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L161 O-1096
Effect of Nitrate of Soda on
Development of the
Halehaven Peach
By
RICHARD V. LOTT
Bulletin 493
UNIVERSITY OF ILLINOIS
AGRICULTURAL EXPERIMENT STATION
CONTENTS
PAGE
REVIEW OF LITERATURE 323
Physical Changes During Fruit Development 323
Chemical Changes During Fruit Development 326
EXPERIMENTAL MATERIALS AND METHODS 329
CHANGES DURING FRUIT DEVELOPMENT 334
Morphological Changes 334
Physical Changes 337
Chemical Changes 347
Effects of Nitrogen Fertilization 361
APPLICATION OF RESULTS 367
NATURE OF GROWTH PERIODS 371
First Growth Period 371
Second Growth Period 372
Third Growth Period 374
Changes in Stone and Kernel 379
SUMMARY AND CONCLUSIONS 380
LITERATURE CITED. . .381
Urbana, Illinois October. 1942
Publications in the Bulletin series report the results of investigations made
or sponsored by the Experiment Station
Effect of Nitrate of Soda on Develop-
ment of the Halehaven Peach
By RICHARD V. LOTT, Associate Chief in Pomology
"NOWLEDGE of the changes which the fruit undergoes during
its development is essential to the devising of the most desirable
orchard practices. Altho there are numerous publications deal-
ing with fruit-bud differentiation, fruit setting, fruit drops, the effect
of soil-management methods upon the quantity and grade of the
resulting crop, changes occurring in storage, and similar problems,
relatively little study has been given to the physical and chemical
changes which occur in the fruit during its development from the
blossom to the ripe fruit.
The work here reported was conducted in the peach orchard of
the Department of Horticulture at Urbana, Illinois, in 1938, with the
object of obtaining some information on the physical and chemical
changes which occur in the development of the peach fruit from the
blossom to the soft ripe stage of the flesh, and the effect of a differ-
ential supply of available nitrogen upon them. In addition to this, some
study was made of the morphological changes in the fruit thruout the
season.
REVIEW OF LITERATURE
The principal contributions to the existing knowledge of the
development of the fruit of the peach follow.
Physical Changes During Fruit Development
Strasburger, 61 * referring to stone fruits, said:
". . . . they can be readily used for studies in the development of the various
tissues, especially of the endocarp in the process of 'stoning' which takes place
at a definite period of their growth, during which, for some little while, the
young fruit does not increase in size."
Likewise, Sorauer 60 * observed in 1895, "In the case of stone fruits
.... during the period in which the stone is formed the fruit does
not increase much in size."
Thus some conception of periodicity of size increase in stone fruits
existed long before the first of the modern investigations on the subject.
It is to relatively recent studies, however, that we must give credit for
our present knowledge of the subject.
*These numbers refer to literature citations on pages 381 to 384.
323
324 BULLETIN No. 493 [October,
The first comprehensive attempt to determine the seasonal trend
of development in the peach fruit was that of Connors, 13 * who, in
1918, measured at weekly intervals the suture diameter of the fruits of
nine varieties ranging from early to late in season of ripening. Meas-
urements were started one week before the stones began to harden and
were continued until harvest. The following year he determined the
increase in suture diameter in Greensboro, Belle, and Elberta varieties,
beginning before petal fall and continuing to 61 days after bloom. His
conclusions are given below in some detail because they have been
substantiated in the main by several other investigators and form the
historical basis for any discussion on peach fruit development.
"The growth of the fruit of peaches is quite definitely divided into three
stages Stage 1 : Rapid development of the fruit apparently due mainly to
increase in size of the seed part. Up to the 44th day from the beginning of
measurements. Stage 2: Rest period during which the seed is formed and the
stones become hard. Stage 3: Period of rapid growth of flesh to maturity,
beginning four to five weeks before ripening time.
"The stage subject to the greatest modification is Stage 2. This may be
only one or two weeks, in the case of the early clingstone varieties, or it may
be 4 to 7 weeks in the case of the later ripening varieties."
The term "seed," as Connors used it, apparently included stone
and kernel. He also pointed out that Mayflower, Early Wheeler, and
Greensboro were typical of varieties ripening before Carman in that
they did not produce full-sized cotyledons. This phenomenon has
since received considerable attention in discussions of peach fruit
development.
Blake 5 * studied size increase in Elberta from blossom bud to
maturity during the season of 1925. His data substantiated the theory
of three growth periods described by Connors. He also found that the
polar diameter increased more rapidly than the suture and cheek
Note. In this Bulletin the following terminology is used:
FLESH the pulpy part of the fruit outside the stone ; botanically the fleshy
pericarp.
STONE the inner portion of the fruit that becomes hard and stonelike ;
botanically the endocarp.
KERNEL the integuments and their contents ; the ovule or seed.
POLAR DIAMETER the greatest distance from base to apex of the fruit.
SUTURE DIAMETER the greatest distance between ventral and dorsal sutures.
CHEEK DIAMETER the greatest distance thru the fruit at right angles to the
suture diameter.
GROWTH PERIOD a relatively definite interval during the time the fruit is
increasing in size. These growth periods will be referred to as the first growth
period, second growth period, and third growth period ; or simply as the first,
second, or third period.
FINAL SWELL the rapid increase in the size of the fruit in the last few
weeks before harvest, coincident with the third growth period.
C TREE, FRUIT, LEAF, etc. the tree (or its parts) that received no fertilizer.
N TREE, FRUIT, LEAF, etc. the tree (or its parts) that received fertilizer.
1942] DEVELOPMENT OF HALEHAVEN PEACH 325
diameters during the first 51 days, then the suture diameter increase
was the most rapid of the three, and during the final growth period
both the suture and cheek diameters increased more rapidly than the
polar diameter.
In 1926 Dorsey and McMunn 18 * made the first study of the develop-
mental relationships of the different parts of the fruit, using Elberta.
They also found that the fruit increased in length in three periods
similar to those described by Connors. During the first period the
stone and kernel reached nearly maximum length. The endosperm
made its most rapid growth in the second period. The cotyledons
began rapid growth about the 60th day after bloom and reached full
length in less than a month, about two weeks before flesh maturity.
The beginning of the second growth period coincided with the initia-
tion of hardening in the stone, the attainment of approximately maxi-
mum length by the kernel, and the start of rapid growth in the
endosperm.
Blake et a/ 6 * reported polar, suture, and cheek diameter measure-
ments for the seasons 1929 and 1930 on Elberta fruits from high-
carbohydrate and from high-nitrogen trees. The fruits in both seasons
showed the usual three periods of size increase. The high-nitrogen
fruits had a longer third period, resulting in several days later ripening.
That all peach varieties may not have periodic growth is shown by
the data of Lilleland 37 * on the seasonal increases in cheek diameter in
seven varieties. He found periodicity in Elberta, Lovell, St. John,
Levi, and Late Champion but not in Sneed and Triumph. He thought
that time of maturity was not definitely responsible for the occurrence
of periodicity, since St. John, an early variety, exhibited distinct
periodicity. Tukey 87 * reported a second period of nine days' duration
in Triumph in New York. This discrepancy with Lilleland's results
may be due to the method of measurement since Tukey based growth
on polar diameter increase whereas Lilleland used suture diameter in-
crease. As reported by Blake, 5 * the peach fruit increased more rapidly
in polar diameter early in the season than later, but suture diameter
increased more rapidly after the rate of polar diameter increase had
begun to slow down. Volume measurements would have to be used to
determine definitely whether the Triumph variety had periodicity of
size increase.
In 1932 the writer 39 * studied the development of Hiley from the
beginning of stone hardening until flesh maturity. To the usual
diameter measurements were added volume, green-weight, and dry-
weight determinations. While a second growth period was evident from
the diameter, green weight, and volume data, it was not nearly so
clearly defined as has been reported for other varieties. When dry
weight was used as the measure of growth there was only a suggestion
326 BULLETIN No. 493 [.October,
of a second period. The dry weight of the stone increased most
rapidly during the second period and reached a maximum at its end.
Likewise, the kernel was increasing steadily in dry weight at this time
and made its most rapid increase near the end of the period. Similar
results were obtained in 1933 with Hiley and Elberta and in 1934 with
Elberta. When growth was measured on the basis of dry-matter
increase there was no definite second growth period. If such a period
had been present it would have been confined to the flesh since the
stone and kernel were both increasing rapidly in dry matter.
The next investigation on this subject was that of Tukey. 67 * In
1933 he measured the length increases of the fruit, stone, and kernel of
five varieties with intervals of 91 to 144 days from bloom to harvest.
In each variety he found the usual three periods of size increase and
also reported the following results: (1) The duration of the first
period was similar in all varieties. (2) the duration of the second
period was directly correlated with the date of ripening, being short-
est in the earliest variety and longest in the latest ripening sort. This
is in agreement with Connors. 13 * (3) Initiation of stone hardening
was almost simultaneous for all five varieties, but hardening was most
rapid in those ripening earliest. (4) Nucellus and integuments in all
varieties reached maximum size near the end of the first growth period.
(5) The embryo development in all varieties was similar, rapid enlarge-
ment beginning at approximately the end of the first period and maxi-
mum size being reached in 29 to 31 days.
Chemical Changes During Fruit Development
The first comprehensive study of the changes which the chemical
constituents of the peach fruit undergo during its development was
made by Bigelow and Gore 4 * in 1905. They analyzed six varieties,
ranging in season of ripening from early to late, at three stages which
they designated as June drop, stone just hardened, and market ripe
(probably what is now known as hard ripe). Three of the varieties
were also analyzed at the full-ripe stage. Their publication includes an
excellent synopsis of the analytical work on peaches which had been
done up to that time. Since none of these former analyses were
extensive, knowledge of the chemistry of the peach really started with
their work. A notable feature of their report was the need they pointed
out for expressing results in amounts as well as on a percentage basis,
a fact since overlooked by some investigators.
The data of Bigelow and Gore show large increases in the solids of
the peach fruit from one sampling date to the next, a marked increase
in percent of solids in the stone and kernel, but a decrease in the
percent in the flesh in the last sample. The sucrose content of the
flesh was very low in comparison with reducing sugars in the first
sample but two to three times as great in the last sample. The amounts
1942] DEVELOPMENT OF HALEHAVEN PEACH 327
of nitrogen and ash increased as the season progressed. The only
determination made on stone and kernel was made for solids content.
The only carbohydrates determined were sugars. The major fault of
their work, one which they recognized and mentioned, was that
samples were not taken more frequently.
In 1905 Van Slyke ct a/ 73 * published extensive analyses of the parts
of fruit trees. They found the following relative amounts of nutrients
in peach fruits, based on the average of the three varieties, Elberta.
Champion, and Hills Chili, at maturity: nitrogen 1.00, phosphoric acid
(P 2 O 5 ) .49, potash (K 2 O) 2.05, lime (CaO) .12, and magnesia (MgO)
.23. Based on percentages, their data show two to three times as much
potash as nitrogen in the flesh, considerably less phosphoric acid, more
nitrogen in the stones than in the flesh, and two to four times as much
nitrogen as phosphorus or potassium in the stones.
Thompson and Whittier, 63 * in a significant but seldom mentioned
study in 1912, pointed out the desirability of determining the relative
proportions of dextrose and levulose in fruits. They found that in the
juice of both green and ripe Belle peaches the percent of levulose and
dextrose was approximately equal. In the green fruit, however, the
percent of reducing sugars (levulose and dextrose) was more than
eight times that of sucrose, while in the ripe fruit the percent of
sucrose was over twice that of the reducing sugars. In 1913 the same
authors 64 * published the results of a study in which the juice of peaches
was analyzed at intervals starting one month before the stone hardened
and continuing to flesh maturity. They found that levulose and
dextrose occurred in approximately equal quantities but in no case did
the dextrose exceed the levulose. The percent of these two sugars
decreased uniformly toward maturity, accompanied by a corresponding
increase in sucrose.
The next contribution to the knowledge of chemical changes
during development in the peach was that of Appleman and Conrad. 3 *
They studied the pectin changes in Crawford peaches from the hard
ripe to the soft ripe stage. They concluded:
"The amount of soluble pectin formed from the insoluble protopectin in the
cell walls so closely paralleled the degree of softening of the peaches during
ripening that this transformation may be considered the chief process respon-
sible for the softening of the fruit. Other processes besides this pectic change
are probably involved in the extreme softening of overripe peaches."
Kokin 35 * studied the sugar changes in the flesh of Elberta and
Champion during the last 84 days of the season of 1928. His data for
both varieties show the usual low percentages of sucrose early in the
season and an increase to maturity. In Elberta there was more glucose
than fructose up to the last three weeks, then there was a drop in
glucose but a continued increase in fructose, so that the percent of
fructose was nearly 50 percent greater at harvest. At that time fructose
328 BULLETIN No. 493 [October,
constituted nearly 20 percent of the total sugar. In Champion, glucose
exceeded fructose in the first two samples only, then decreased rapidly
and was entirely absent during the last month. Fructose continued to
increase and made up nearly one-third of the total sugars at maturity.
These results are not in agreement with those of Thompson and
Whittier cited above. The lack of agreement may be due entirely to
difference in the varieties studied and thus shows the danger of draw-
ing widespread conclusions from the results of study of a single
variety.
In 1930 Nightingale et a/ 51 * published the results of a study of the
comparative chemical composition of the flesh of Elberta fruits from
high-carbohydrate and high-nitrogen trees. Only the last seven weeks
of the season were included. The outstanding results were a higher
percentage of sugars, soluble pectin, protopectin, cellulose, and dry
matter at maturity in the flesh of the high-carbohydrate fruits, and
higher percentages of nitrogen and ash in the flesh of the high-nitrogen
fruits.
In an investigation of the development of Hiley from stone harden-
ing to flesh maturity, conducted by the writer 39 * in 1932, the analysis
of stone and kernel was included in the study of chemical changes
occurring during development. By expressing results on the basis of
amounts as well as in percentages, a more comprehensive picture of
the seasonal trend of the constituents was obtained. The most sig-
nificant feature of the flesh-stone relationship was the rapid accumla-
tion of hemicellulose in the stone, while all carbohydrates in the flesh
were increasing slowly and the sugars in the stone were decreasing.
This relationship, coupled with the fact that the period of greatest
accumulation of sugars in the flesh (the final swell) coincided with a
decrease in all carbohydrates in the stone, indicated that the stone was
the dominant part of the fruit until it reached its maximum carbo-
hydrate concentration, which was also its point of maximum dry
weight. The decrease in dry weight and in all determined materials
in the stone during the final swell of the flesh showed that the stone
reached physiological maturity before the flesh. The kernel increased
rapidly in ether extract during the third growth period of the flesh
after the embryo had attained its greatest size. The amount of ether
extract in the kernel at maturity was more than twice that of all of its
other determined constituents. Further study 40 * with Hiley and Elberta
in 1933 and with Elberta in 1934 confirmed these results.
In 1935 Lott and Ashley 41 * compared the development of five
varieties varying from early to late in season of maturity. The size,
fresh and dry weights, and composition of each variety when ripe were
compared with these characteristics in the late-ripening Elberta on the
same date. It was found in the early varieties that the stone continued
to increase in dry weight until harvest, instead of reaching a maximum
1942] DEVELOPMENT OF HALEHAVEN PEACH 329
in the second period or early in the third period, as Elberta did. This
competition for materials between the flesh and the stone in the third
growth period was associated with small fruit size and low sugar con-
tent in the flesh at maturity. The percent of sugar in the flesh
increased directly with the date of ripening. The Elberta kernels
increased much more rapidly in dry weight, nitrogen, and ether extract
than the earlier varieties. The amount of each of these was greater
in the Elberta kernels on the ripening date of any earlier variety than
in the kernels of the earlier variety. This work showed the impos-
sibility of applying directly to any variety the information obtained
from another variety having a different season of maturity. It is also
quite possible that varieties having the same season of ripening differ
enough in their development to make the study of individual varieties
desirable.
The literature which has been reviewed above shows that since the
work of Connors 13 * the conclusion has been reached by nearly all inves-
tigators of the subject, that the fruits of the peach have three fairly
distinct periods of size increase. When the present problem was
initiated, no one had followed both the physical and the chemical
changes in the fruit or its separate parts from bloom to flesh maturity.
This investigation was undertaken in order to supply some of this
needed information.
EXPERIMENTAL MATERIALS AND METHODS
Materials
For use in this investigation two adjacent six-year-old Halehaven
trees were selected. They were apparently of the same size and vigor
and had made a vigorous growth in 1937, the length of the longer
terminal shoots ranging from 10 to 18 inches. There was an abundant
crop of fruit buds, and approximately 50 percent of the nodes on the
longer shoots had two buds. Only an occasional bud failed to survive
the winter of 1937-38.
The soil is a brown silt loam underlain with clay loam at a depth
of 8 to 10 inches. The slope of approximately 3 percent is toward the
southwest and away from the trees used. A cover crop of rye, sowed
in the fall of 1937, was allowed to head and was then disked into the
soil on June 3. This was followed by a crop of natural vegetation,
which was mowed August 1. The vegetation under the trees was
mowed with a scythe as frequently as was necessary to keep it down to
a height of a few inches.
To determine the effect of the available-nitrogen supply upon fruit
development, a difference in vigor between the two trees was estab-
lished by making two applications of nitrate of soda to one of them.
330
BULLETIN No. 493
[October,
The applications, of 5 pounds each, were made March 28, 17 days be-
fore full bloom, and June 4, when the stone was beginning to harden,
51 days after bloom. The fertilizer was scattered uniformly over the
surface of the ground under the tree, extending from the trunk to the
tips of the branches. Rain fell in the night following each application,
so the material undoubtedly went into solution within 10 to 12 hours
after application.
The daily mean temperature and the precipitation are shown in Fig.
1. The mean temperature for March was 3.2 degrees above normal,
with the result that the buds developed somewhat more rapidly than
in most seasons. A cooler period started April 1, with the following
minimum Fahrenheit temperatures: April 1, 33; 2, 30; 3, 26; 4,
30 ; 5, 31 ; 6, 33 ; 7, 30 ; 8, 34 ; 9, 30 ; 10, 32. The buds developed
very slowly during this period. Rain which fell on April 8 froze on
LESS THAN 3/100 INCH NOT SHOWN
FIG. 1. DAILY TEMPERATURES AND RAINFALL AT URBANA
DURING GROWING SEASON, 1938
the trees, resulting in a coating of ice approximately }4 inch thick on
all parts of the tree. This remained on the trees for nearly 24 hours,
and melted on the 9th, which was clear and warmer. The petals were
well colored and the buds almost ready to open, but no buds were
killed by the ice and accompanying cold. Clear and increasingly
warmer weather followed. The trees had a few open blossoms on
April 13, were about one-half in bloom on the following morning, and
were in full bloom by midafternoon. Only a few buds opened after
this date. The weather of April 13 and 14 and for several days there-
after was warm and sunny, with abundant bee activity and favorable
conditions for growth following pollination. Consequently April 14 is
considered the date of full bloom and all data are referred to that as a
base date.
1942\ DEVELOPMENT OF HALEHAVEN PEACH 331
There was no evidence of a deficiency of moisture at any time
during the season. The most extended period of light rainfall extended
from April 9 to May 7. Apparently there was an adequate moisture
supply during this period, since there was no evidence of wilting of the
peach leaves nor of nearby vegetation.
Methods
Sampling. In all collections the samples were taken from the
two trees within 30 minutes, and were then taken to the laboratory
about five minutes distant for preparation. All samples were collected
in the early morning, not later than 8:30 a.m. during the first few
weeks after bloom and before 7:30 a.m. thereafter.
Fruit samples. Samples were collected at intervals of approxi-
mately one week from full bloom to the soft ripe stage of the flesh,
taking care to include fruits from all portions of the tree. The first
sample was taken on April 14, when a sample of 300 flowers was
collected from each tree. The pistil was removed by separating the
base of the ovary from the calyx cup with a sharp scalpel. Thereafter
200 to 300 fruits were included in each sample until May 12 and the
whole sample preserved for analysis. Beginning with that date a
sample of 75 to 100 fruits was picked from each tree. The fruits were
taken to the laboratory, weighed individually, and grouped into classes
of 2-gram intervals until July 21 and in classes of 5-gram intervals
thereafter. Since the objective was to measure the mean condition on
the tree, the smallest class and the largest class was discarded and a
25-fruit sample selected from the remaining classes, the number of
fruits taken from each class being proportional to the total population
of that class.
The selected sample was weighed to obtain the fresh weight per
fruit ; the polar, suture, and cheek diameters were measured with a
caliper; and the volume determined by displacement in water in a
graduated cylinder. Because of the small size of the fruit, no separa-
tion into its component parts was attempted before May 12. Beginning
with the May 12 sample (28 days after bloom) the kernel was removed.
The stone was first hard enough to separate from the flesh on June 10
(57 days after bloom), and thereafter the fruit was separated into
the three parts: flesh, stone, and kernel.
After the weight, diameters, and volume of the fruit were de-
termined, the flesh was removed from the stone and placed at once in
a ventilated electric oven at 90 C. and left for 30 minutes, after which
it was transferred to a similar oven kept at 65 C. and left until a
constant dry weight was reached. The stones with the included kernels
were weighed, measured, their volume determined, separated from
the kernel by cracking, and the weight, diameter, and volume of the
kernels obtained. After securing the above data, stones and kernels
332 BULLETIN No. 493 [October,
were dried in the same manner as the flesh. The weight and volume of
the flesh were determined as the differences between the weights and
volumes of the fruit and those of the uncracked stone. Likewise, the
weight and volume of the stone were calculated as the differences
between those of the uncracked stone and the kernel.
Preparation. The first four fruit samples were ground by hand
in a mortar, on account of the small size of the dry sample. They
were reduced to pass a 60-mesh sieve. Finer grinding was impractical
because of the great amount of epidermal hairs present. In all later
samples the flesh (including the stone until it was hard enough to
separate) was ground in a Wiley mill to a particle diameter to one-
half millimeter. Further grinding was impossible because of the hygro-
scopic nature of the material, especially as maturity was approached.
These samples were further reduced before analysis, as explained
later.
The stones were cracked in a burr mill into pieces 1 to 3 millimeters
wide and then ground in a ball mill to pass a 100-mesh sieve. The
kernel samples were all ground by hand in a mortar, since the samples
were relatively small. After ether extraction, they were again ground
to homogenize the extracted residue before further determinations
were made.
The ground samples were stored in the dark in tightly stoppered
sample bottles until analyzed. Duplicate samples were used for all
determinations.
Dry matter. This was obtained by drying, as previously ex-
plained. The dried samples were weighed and the percent of dry
matter calculated on the basis of the original fresh weight.
Ash. A one-gram sample of the dry powder was ignited to a
white ash in a porcelain crucible over a Bunsen flame. 38 *
Ether extract. Two-gram samples of the dry ground kernels were
extracted for 20 hours with anhydrous ethyl ether in a standard con-
tinuous extraction apparatus. The kernels were the only samples upon
which this determination was made, since previous experiences had
shown that the flesh and stone did not contain measurable quantities
of the substances extractable by ether.
Nitrogen. Only total nitrogen was determined. The Kjeldahl
method modified to include nitrates, as described by Loomis and
Shull, 38 * was used on 1-gram samples.
Sugars. Extraction. After considerable preliminary investigation,
the following method of extraction was found to be most satisfactory
under the prevailing conditions for the flesh and kernel but was not
necessary for the stone samples.
1942} DEVELOPMENT OF HALEHAVEN PEACH 333
A 2-gram sample of the dry material was ground in a porcelain
mortar with a minimum of water until it was a finely reduced homo-
geneous mass. The ground sample was washed onto filter paper in. a
4-inch Buchner funnel and the filtrate carried thru with slight to
moderate suction. The colloidal material in the peach flesh and kernels
made suction necessary. The sample was washed ten times with small
quantities of water. Tests showed that this removed all of the sugars.
The stone samples were extracted by placing 2-gram samples on
filter paper in 75-mm. glass funnels and washing ten times with small
quantities of water. These samples could be washed fairly rapidly by
this method.
Determination of reducing sugars. In all cases the extracted solu-
tion was cleared with 1 cc. of a saturated solution of neutral lead
acetate, filtered, thoroly washed, deleaded with a saturated solution of
potassium oxalate, filtered, and made to volume. Duplicate aliquots of
the filtrate were taken for the determination of reducing power.
Reduction was carried out according to the Munson-Walker condi-
tions* 4 * and the amount of reduced copper determined by the Shaffer-
Hartman method. 58 * All carbohydrates were calculated and expressed
as dextrose.
Determination of total sugars. A 50-cc. aliquot of the cleared and
deleaded sugar solution was pipetted into a 100-cc. volumetric flask, and
25 cc. of water and 5 cc. of concentrated HC1 added. The flasks were
placed immediately in a water bath at 70 C. and left in the bath for
five minutes after the contents reached a temperature of 67 C.
The flasks were then removed, cooled at once, nearly neutralized, and
duplicate 50-cc. aliquots taken for the determination of reducing power.
Sucrose. The reducing power obtained in the total sugar determina-
tion minus that of the reducing sugar determination was considered to
be sucrose.
Starch and dextrin. These were determined on the residue from
the sugar extraction, following the general procedure outlined by
Loomis and Shull, 38 * using fresh saliva and completing hydrolysis by
refluxing in 2yi percent HC1 for 2 hours. Reducing power was
determined as for sugars.
Hemicellulose. While this should more correctly be designated
as water-insoluble acid-hydrolyzable materials, the more convenient
term "hemicellulose" will be used.
The residue from the starch-dextrin extraction was refluxed for
2 hours in 2i/ percent HC1, filtered, washed, cooled, nearly neutralized,
cleared and deleaded, made to volume and duplicate aliquots taken for
the determination of reducing power.
334 BULLETIN No. 493 [October,
CHANGES DURING FRUIT DEVELOPMENT
Morphological Changes
A summarized description of the gross morphological changes
which occurred during the season in the fruit is given in Table 1. A
similar summary is given in Table 2 for shoot and leaf growth. This
material is included at this point in order to provide a background for
the detailed discussions on the growth and chemical changes in the
fruit. Certain morphological aspects of fruit development which could
not easily be included in Table 1 will be considered at this time.
At full bloom the two ovules were the same size, with the exception
of an occasional ovary in which one ovule was slightly smaller. Seven
days later one ovule was noticeably thicker than the other and slightly
TABLE 1. SEASONAL DEVELOPMENT OF FRUIT OF Two PEACH TREES AT
URBANA, ILLINOIS, 1938
Days
Date after Condition
bloom
Apr. 14 Full bloom.
18 4 Half of petals fallen.
21 7 All petals fallen, stamens erect, anthers dry, tip % inch of style dry.
22 8 Shuck abscission zone evident in 25 percent of N fruits, none in C fruits.
25 11 Shuck abscission zone evident in 50 percent of fruits, stamens dry.
27 13 Shucks abscised in all fruits, shuck withered more advanced in N fruits tip
one-third to one-half of style dry.
28 14 Shucks brown, withered.
May 5 21 Shucks all off; styles mostly abscised, more from N than from C fruits.
June 2 49 Stone beginning to harden at tip, down ventral suture, and inner epidermis.
6 53 Endosperm first evident macroscopically. Nucellus and integument near maxi-
mum size.
June 10 57 Stone first hard enough to separate from flesh, still somewhat soft at base and
next to flesh at tip. Embryo first evident macroscopically.
29 76 Endosperm full length of nucellus in most cases, embryo half as long.
July 7 84 Stone at maximum hardness as measured by resistance to cutting. Embryo Mo
length of nucellus, endosperm a thin layer. Integument started to color
cream with slightly darker tip. Third period of flesh development started.
15 92 Embryo filling integuments except for very thin layer of endosperm.
21 98 Blush present on some C fruits, none on N. Integument dark cream, slightly
darker at tip.
29 106 Ground color of C fruits yellow-green, 50 percent overlaid with red. Flesh lemon-
yellow with some red in it and red at stone. Ground color of N fruits still
quite green, with 10 percent overlying red. Integument same color as on July 21 .
Aug. 4 112 Ground color of C fruits yellow, 90 to 100 percent overlaid with crimson. Con-
siderable red in flesh and adjacent to stone. Ground color green in N fruits,
50 percent overlaid with crimson, less red in flesh than C.
9 117 C fruits soft ripe, ground color orange-yellow overlaid with deep crimson on ex-
posed side, with streaks and splashes of carmine and crimson on shaded side,
very little ground color showing. Flesh orange-yellow, with red conspicuous
along main vascular bundles and at stone. Integument mostly dark cream,
some with light brown chalaza, a few entirely light brown.
15 123 N fruits soft ripe, same general appearance as C fruits on Aug. 9, not as highly
colored but as attractive, less red in flesh. Half of integuments light brown,
others dark cream or dark cream with light brown chalaza.
C check tree. N - tree treated with nitrate of soda.
1942] DEVELOPMENT OF HALEHAVEN PEACH 335
longer ; the smaller ovule was twice as long as it was at bloom, but
it was the same width as at bloom and slightly thinner. One month
after bloom the suppressed ovule w r as still white in color and four
times as long and twice as wide as at bloom but only about half as
thick. Whether this difference in size was due to continued growth
or to the flattening of the suppressed ovule against the stone by the
growth of the other ovule was not determined. This information
indicates the possibility of being misled concerning the growth of the
suppressed ovule because of the more rapid development of the normal
ovule after bloom. Harrold 32 * stated that the two ovules in Carman
developed equally until about three days after bloom, when one
TABLE 2. SEASONAL DEVELOPMENT OF SHOOTS AND LEAVES OF Two PEACH TREES
AT URBANA, ILLINOIS, 1938
Days
Date after Condition
bloom
Apr. 14 Rosette of leaves up to % inch long in C, up to 1 inch in N.
May 5 21 N leaves darker and larger than C leaves from here to end of season.
12 28 C shoots up to 3 inches long; N shoots up to 4 inches long.
June 8 55 C shoots up to 5 inches long, approximately 90 percent ceased elongating.
N shoots up to 8 inches long, large percentage still elongating, those under 3
inches ceased elongating.
22 69 C shoots all ceased elongating.
N shoots up to 4 inches long ceased elongating, others decreasing in rate of
elongation.
July 1 78 N shoots above 6 inches long still elongating. Some of longest with lateral
secondary shoots.
14 91 N shoots above 10 inches long still elongating.
21 98 N shoots above 10 inches long still elongating slowly.
29 106 N shoots all had ceased elongating.
Aug. 10 118 C leaves had decreased in dry weight compared with July 1 (start of third growth
period).
N leaves were still increasing in dry weight as compared with July 1.
stopped. Ragland 57 * reported that one ovule was often smaller than the
other in Phillips Cling at full bloom, and that this difference prevailed
for 10 or 12 days, when the smaller one aborted. This discrepancy
with the present work may be due to the varietal or the environmental
difference or both.
The arrangement of the bundles in the pedicel was essentially that
described by Bonne. 7 * From the vascular cylinder at the base of the
fruit there were 10 to 12 bundles that entered the stone and branched
from it into the flesh at various levels. In addition to these bundles
the stone also contained the bundles that extended from the vascular
cylinder at the base of the fruit to the ovules, one to each ovule. These
are the bundles that Ragland 56 * called funicular bundles. The major
bundles exterior to the stone were the two large ventral bundles lying
in deep grooves, one on each side of the ventral suture of the stone,
and the dorsal bundle lying in a groove along the dorsal suture. The
336 BULLETIN No. 493 [October,
ventral and dorsal bundles diverged from the stone just back of its tip
and continued into the style. There were a few small bundles passing
directly from the vascular cylinder into the flesh, but the main vascular
system of the flesh developed by the branching of the bundles entering
it from the stone and from the dorsal and ventral bundles.
In the young peach fruit at full bloom the principal vascular
bundles extended the full length of the fruit and continued on into
the style. Sixteen days after bloom it was apparent that the interior
cells of the vascular bundles in the tip one- fourth of the fruit had
broken down and disintegrated to form ducts which rapidly became
more prominent. They were easily distinguished by a low-power
microscope 22 days after bloom. Thereafter they gradually appeared
thruout the flesh but were always most prominent in the tip one-third
of the fruit. These ducts later became filled with a gummy substance
which was probably a pentose, since the peach is known to form such
substances. 65 * Ducts of a similar nature were described by Ragland. 56 *
He found that they appeared at the apex of the fruit two to three
weeks after full bloom and four weeks later had appeared thruout
the flesh.
No detailed study was made of the development of these ducts. It
seems probable that their formation was due, at least partly, to the
inability of the vascular bundles to undergo the very significant
stretching which results from the rapid increase in the size of the
fruit.
The differentiation of stone tissue from flesh was evident at full
bloom. The outline of the stone could be observed macroscopically
two weeks after bloom. The stone began to harden first at the tip,
down the ventral suture, and in the inner epidermis, with the tip
slightly in advance of the other regions. Tests with alcoholic phloro-
glucin showed lignin formation accompanying hardening. Hardening
progressed outward from the inner epidermis and from the tip toward
the base. If the theory is accepted that the carpel is a modified leaf or
leaf -like structure, it would be expected that the stone would harden
first at the tip, since Fitzpatrick 27 * has shown that, anatomically, the
peach leaf matures first at the tip and then progressively toward the
base.
The morphological details of ovule development after bloom were
in agreement with the description of Pechoutre. 52 * The more obvious
features of its development are given in Table 1.
The skiri and pubescence apparently followed the growth trend
described by Dorsey and Potter, 24 * altho this was not studied in detail.
Microchemical tests showed the basal one-fourth to one-third of the
hairs to be lignin, with the remainder giving a positive test for cellulose.
194Z\ DEVELOPMENT OF HALEHAVEN PEACH 337
Physical Changes
Diameter. Both the C and the N fruits increased rapidly in
diameter up to the 57th day after bloom, somewhat more slowly from
the 57th to the 76th day, then at an increasing rate until a few days
before harvest (Table 3). Hence the usual three periods of size
increase were evident. There was a particularly noticeable acceleration
from the 98th to the 112th day in the C fruits and from the 98th to
119th day in the N fruits. The period of slow growth was more
pronounced in the polar diameter than in the suture and cheek
diameters. During the early part of the third growth period all three
diameters increased at approximately the same rate, but during the
latter part of the period the suture and cheek diameters began to
increase more rapidly than the polar diameter so that they both
exceeded it at harvest.
The nitrogen had little effect on the diameter trend except that the
fertilized fruits were usually slightly larger and had a 4-percent
greater average diameter at harvest than the C fruits. The larger
size of the N fruits at harvest was due to the fact that these fruits
continued to grow after the check fruits had ripened (Table 3 and Fig.
2). The data of Blake et a/ 6 * show this same condition in fruits
growing under a wider range of nitrogen nutrition than the fruits in
this investigation.
The different rates at which the three diameters increased during
the season shows that the use of any one of them alone may lead to
erroneous conclusions concerning rate of size increase. This is espe-
cially true of the long fruited varieties such as Elberta, when only the
polar diameter is used, as has sometimes been the case. 67 * The effect
of nutritional level would also be a factor in such cases, since the
nitrated fruits were broader in relation to length than the C fruits.
The transition from one growth period to the next was a gradual
process, but it was more distinct between the first and second periods
than between the second and third. This was also the case in previous
work by the writer on this subject. 39 - 40 * Lilleland 37 * says, "The changes
in rate of growth are generally quite abrupt as the fruit passes from
one period to the other." Tukey 67 * also pointed out that the change
from the first to second period was abrupt. This is not in agreement
with the present data.
Volume. When volume increase was used as the measure of
fruit development, the same period of reduced rate of increase occurred
as with diameter measurements (Table 3 and Fig. 2). The N fruits
were 23 percent larger than the C fruits at harvest, but until near
harvest no appreciable difference occurred. The fact that, in contrast,
the diameter difference at harvest was only 4 percent shows that vol-
338
BULLETIN No. 493
[October,
iiisiSiss ssss sssss :ss:
Dry weigh
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1942\ DEVELOPMENT OF HALEHAVEN PEACH 347
tions of water content, it is even possible to obtain a decrease in fresh
weight while the amounts of solids are actually increasing.
Diameter measurements must be resorted to when the development
of specific fruits on the tree is followed, but in such cases the dry-
matter increase in comparable fruits must be determined in order to
make correct physiological interpretation possible.
The developmental history of flesh, stone, and kernel, as depicted
in Table 4 and Figs. 3 and 5 emphasizes the necessity for dry-
matter determinations and for separating the fruit into its parts in
studies of its physiological development. Increases in dry-matter per-
centage in the stone and the kernel in the second and third growth
periods made possible the most rapid dry-matter increases after these
parts had reached nearly their maximum volumes and fresh weights.
Measurements of size and fresh weight could not show these increases,
nor could they show the increase in dry-matter percentage in the flesh
in the second growth period and its decrease in the third period. This
is in agreement with previous work. 40 *
Measurements are particularly inadequate as indices of the growth
of the kernel because of the internal tissue changes which occur during
development, as shown in Table 1. For example, the kernel near the
end of the first growth period is a vastly different organ than at the
beginning of the third growth period. The inclusion of measurements
of endosperm and embryo development would provide little informa-
tion of their metabolic activity. There seems to be no good reason for
relying upon diameter or volume determinations in the stone and
kernel, since the fruit must be destroyed to obtain them, and securing
the dry weight merely adds the simple operations of weighing and
drying.
Chemical Changes
The chemical data secured from this investigation are presented as
percentages of fresh weight and as amounts per fruit or fruit part.
Percentages of dry weight are also given in Tables 17 and 18 for
reference. Expressing results solely on a percentage basis does not
always give a true picture of the seasonal activity of any particular
constituent. This is especially true of organs, such as fruits, which
increase many times in mass during the course of their development.*
Sugars. Altho it is possible that reducing substances other than
sugars were present in the extracts, it is probable that the quantity of
them was small. Therefore the term "reducing sugars" will be used
here rather than the more cumbersome but perhaps more correct term
"free reducing substances." Because of the relationship that existed
*In this publication the term amount refers to grams per 100 fruits ; per-
cent refers to fresh weight percentage; and content refers to both amount and
percent when they have the same seasonal trend.
348
BULLETIN No. 493
TABLE 9. SUGAR CONTENT OF PEACH FRUIT
[October,
Percent of fresh weight
Grams per 100 fruits
Growth
period
Date
col-
lected
Days
after
bloom
C
N
C
N
Re-
ducing
sugars
Su-
crose
Re-
ducing
sugars
Su-
crose
Re-
ducing
sugars
Su-
crose
Re-
ducing
sugars
Su-
crose
Flesh*
I
4-14
2.74
.47
2.84
.42
.42
.07
.43
.06
4-21
7
1.00
.34
.93
.31
.02
f .01
.02
.01
4-28
14
.91
.30
.83
.31
.07
.02
.06
.02
5-5
21
1.90
.14
1.86
.13
.94
.07
.93
.07
5-12
28
3.66
.17
3.51
.10
3.95
.18
4.18
.12
5-19
35
3.44
.10
3.34
.13
10.63
.31
11.52
.45
5-26
42
3.41
.15
3.31
.15
27.63
1.21
28.07
1.28
6-2
49
3.99
.35
3.63
.26
60.61
5.32
59.93
4.29
II
6-10
57
4.07
.44
3.76
.42
62.11
6.71
57.30
6.40
6-16
63
4.24
.32
3.77
.40
69.62
5.26
64.66
6.86
6-22
69
4.54
.15
4.12
.33
87.21
2.88
80.09
6.42
6-29
76
4.22
.26
4.06
.27
92.67
5.71
88.31
5.87
III
7-7
84
4.05
.54
3.87
.67
114.94
15.32
108.24
18.74
7-15
92
3.86
.45
3.85
.43
146.90
17.14
145.15
16.21
7-21
98
3.69
1.09
3.67
1.03
186.12
54.98
182.69
51.28
7-29
106
3.91
1.67
3.61
1.69
307.09
131.16
270.43
126.59
8-4
112
3.94
2.09
3.59
2.52
431.63
228.96
389.91
273.70
8-9
117
3.45
4.50
420.59
548.59
8-11
119
3.05
4^16
444!65
605! 65
8-15
123
2.93
4.94
435 . 43
734.13
Stone
II
6-10
57
2.50
.28
2.49
.76
13.48
1.50
14.17
4.32
6-16
63
2.06
.19
1.98
.22
11.41
1.06
11.74
1.31
6-22
69
1.30
.55
1.20
.35
7.88
3.33
7.62
2.22
6-29
76
1.06
.35
.90
.65
6.64
2.20
5.96
4.30
III
7-7
84
.81
.42
.72
.09
5.23
2.72
5.01
.63
7-15
92
.72
.17
.66
.11
5.02
1.18
4.87
.81
7-21
98
.66
.11
.68
.11
4.37
.73
4.98
.80
7-29
106
.67
.12
.61
.09
4.50
.80
4.31
.64
8-4
112
.63
.18
.51
.11
4.18
1.20
3.36
.73
8-9
117
.52
.20
3.03
1.17
8-11
119
!ii
'.12
2^66
'[77
8-15
123
.42
.11
2.54
.66
Kernel
I
5-12
28
2.11
1.42
1.80
1.56
.08
.05
.07
.06
5-19
35
1.03
.63
.97
.70
.11
.06
.12
.08
5-26
42
.75
.31
.72
.32
.17
.07
.19
.09
6-2
49
.71
.20
.71
.30
.30
.09
.36
.15
II
6-10
57
.64
.30
.56
.30
.36
.17
.35
.19
6-16
63
.63
.26
.54
.27
.35
.15
.33
.17
6-22
69
.68
.26
.56
.23
.38
.15
.34
.14
6-29
76
.87
.55
.73
.68
.50
.32
.45
.42
III
7-7
84
.93
1.00
.74
.98
.54
.57
.47
.62
7-15
92
.69
.76
1.53
.53
1.00
.45
1.00
.35
7-21
98
.58
.84
1.54
.69
.93
.49
1.00
.45
7-29
106
.51
.78
1.53
.76
.83
.43
.98
.48
8-4
112
.65
.99
1.86
.98
1.00
.60
1.15
.61
8-9
117
.78
2.05
.99
1.14
8-11
119
1.99
\.is
i!ii
.72
8-15
123
2.10
1.65
1.22
.96
N. B. Under "flesh" in this and subsequent tables, 4-14= blossoms; 4-21 to 5-5 inclusive =
entire fruit; 5-12 to 6-2 inclusive = flesh plus stone; 6-10 to 8-15 inclusive = flesh alone. All carbo-
hydrates are calculated and expressed as dextrose.
1942}
DEVELOPMENT OF HALEHAVEN PEACH
349
between reducing sugars and sucrose it seems desirable to consider
their activity together.
The seasonal trend of sugars in the separate parts of the fruit is
shown in Table 9 and Figs. 6 and 7. The relatively small percent and
amount of sucrose in the flesh until well into the third growth period
indicates the continued use of sugars in the metabolism of the fruit.
The processes of cell division, cell enlargement and cell-wall thickening
during this time would require increasingly large quantities of sugars.
Consequently there was no excess available for condensation and stor-
age as sucrose until the above processes had neared completion. During
the third growth period, however, when the fruit was nearing maturity,
the sucrose content increased rapidly and exceeded the reducing sugars
^ 14 21 28 35 42 49 57 63 69 76 84 92 98 106112117123
DAYS AFTER BLOOM
FIG. 6. SEASONAL CHANGES IN PERCENTAGE OF SUGARS IN
FLESH -OF PEACH ON FRESH BASIS
at harvest. This behavior of sugars in the flesh is in agreement with
the results of Nightingale, 51 * Kokin, 85 * and Lott. 39 ' 40 * As was men-
tioned in the literature review, the peach is one of the few fruits in
which sucrose is the predominant sugar in the ripe fruit. That this
condition does not prevail much beyond the soft ripe condition is
indicated by the statement of Tarr 62 * that, "as the 'so-called' dead ripe
stage occurs, the sucrose content decreases very rapidly with a corres-
ponding increase in reducing sugars." Bigelow and Gore 4 * also seemed
to find this condition in stored peaches. This fact, in addition to the
loss of aromatic compounds, is the probable reason for some of the
350
BULLETIN No. 493
[October,
m
B
i
t*
s,
H
r
i
o
u
g
06
|5 1
o*a
33
II
H
fOO'* WfOOOQ O^i
_ '. -r ^-. -| ^. ^^
- 00
~r
Mflro oo
^HI5M'O<*J1
O O *O O -"
^OCOCO fSrot^t^O'*
t^t^O-
w> \c O i
ts (N m ts (S ~~"ts m >ooo <^ e^ t- 1
1942\ DEVELOPMENT OF HALEHAVEN PEACH 351
deterioration in quality as peaches become overripe. The loss of sugars
and acid thru respiration would be an added factor.
The rapidity of influx of sucrose during the final swell is shown
by the fact that 75 percent of the total amount of sucrose in the ripe
flesh accrued in the last 11 days in the C fruits, whereas 65 percent
accumulated in the flesh of the X fruits in the same interval.
The content of reducing sugars in the stone was greater in each
sample than the sucrose; which fact indicates that there was prac-
tically no storage of carbohydrates as sucrose in the stone. The con-
sistent decrease of sugars in the stone thruout the second and third
growth periods does not necessarily show that little sugar entered the
stone during this time, but rather that the sugar probably condensed
immediately to more complex carbohydrates until the maximum dry
weight of the stone was reached, and was translocated to the flesh or
kernel or both thereafter. The above relationship of reducing sugars
and sucrose in the stone, and their seasonal trend, is in agreement with
previous investigations. 39 ' 40 *
In the kernel reducing sugars were more abundant than sucrose
until just before harvest, when the amount became approximately the
same as sucrose. An interesting feature of the trend of sugars in the
kernel was the rapid increase in amount during the first period as the
nucellus and integuments were enlarging to nearly maximum size,
followed by a decrease during the early size increase of the endosperm
and embryo and a very slow rate of increase thereafter until the
embryo had reached nearly its greatest size. The fact that sucrose did
not increase appreciably until the rate of accumulation of ether
extract had materially slowed down is evidence that the sugars were
being used as a source of ether extract.
Starch and dextrin. This carbohydrate fraction formed a com-
paratively small part of the total carbohydrates determined, altho the
values obtained were considerably higher than those reported by
Nightingale 51 * and Tarr. 62 * Comparison of the percentages and amounts
in the flesh emphasizes the possibility of errors in interpretation when
percentage alone is used as the measure of the trend of a constituent.
Altho there was a very large decrease in the percentage in the third
growth period, the amount more than doubled (Table 10).
Microchemical tests showed that in the young fruit there was no
starch in the four or five cell layers of the hypodermis, and that it was
most concentrated in a region of ten to fifteen layers of cells interior
to the hypodermis. It was also abundant at the base of the fruit just
above the point of attachment to the receptacle. Very little could be
detected in the stone or kernel at any time. A positive test in the flesh
was obtained on July 21, 98 days after bloom, but not thereafter. The
region of distribution in the flesh remained the same thruout the
season.
352
BULLETIN No. 493
[October,
siinaj ooi 3d
1942}
DEVELOPMENT OF HALEHAVEN PEACH
353
Hemicellulose. Altho this fraction, as determined, was really
insoluble acid-hydrolyzable materials other than starch and dextrin,
it has frequently been designated as hemicellulose 461 65 * and for con-
venience will be referred to as such in this manuscript.
20
8
16
HEMICELLULOSE
220
-//-M-
7 u
./i_\.\_
PERCENT IN V N
STONE /
/ \ N
120
180
160
140
100
80
60
40
20
7 14 21 28 35 42 49 57 63 69 70 04 92 90 106112117 123
DAYS AFTER BLOOM
FIG. 8. SEASONAL CHANGES IN HEMICELLULOSE CONTENT OF
FLESH, STONE, AND KERNEL ON FRESH BASIS
The data shown in Table 11 and Figs. 7 and 8 emphasize the
importance of expressing results in terms of amounts, as well as in per-
centages, in organs such as fruits, which change appreciably in mass
during the season. Altho the percent of hemicellulose in the flesh
354
BULLETIN No. 493
[October,
MOO'TOOO
O'J'OGOO t
q
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j
n
S
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r
00'1'r-i'^
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ts M m - - ts ts ^> o. -
" ~ >^ t oo oo ob oo
13
o'C
O*
1942]
DEVELOPMENT OF HALEHAVEN PEACH
357
in the kernel than in the stone at harvest shows a greater storage in the
kernel. The decreasing amount in the stone after the middle of the
second growth period shows that the stone reached physiological ma-
r"!l3lR355<' ,'^--*-5- 5IUNL
7 14 21 28 35 42 49 57 63 69 70 84 9298 106112117123
DAYS AFTER BLOCK'
FIG. 9. SEASONAL CHANGES IN NITROGEN CONTENT OF
FLESH, STONE, AND KERNEL ON FRESH BASIS
turity long before the flesh and kernel. These relationships were also
found to exist in the previous work by the author. 40 *
Ash. As might be expected because of the greater size of the
flesh, the amount of ash in the flesh was greater thruout the season
than in the stone and kernel. The percentage in the flesh, however,
was approximately the same as that in the stone, while that in the
kernel at harvest was over four times as great as that in either flesh
or stone (Table 13 and Fig. 10). The amount in both flesh and kernel
358
BULLETIN No. 493
{October,
-1/5IO
I
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1942\
DEVELOPMENT OF HALEHAVEN PEACH
359
had apparently nearly reached a maximum in the last samples, whereas
the stone content decreased thruout the third period.
The consistently greater amount of ash in the N flesh suggests a
slightly more active assimilation as a result of the nitrogen fertilization.
This may have been due to greater transpiration. Childers 12 * has re-
ported that the application of nitrate of soda to apple trees increased
transpiration, and Freeland 28 * found that the ash content of tomato,
bean, and other plants increased with the rate of transpiration. The
7 14 21 28 35 42 49 57 63 69 76 84 92 96 106 112117 123
DAYS AFTER BLOOM
FIG. 10. SEASONAL CHANGES IN ASH CONTENT OF
FLESH, STONE, AND KERNEL ON FRESH BASIS
differences in percent were small, however, the differences in amounts
being due largely to the greater mass of the N flesh, especially in the
last few samples.
Nightingale 51 * found a consistently higher percentage of ash in the
flesh of high-nitrogen fruits than in the flesh of high-carbohydrate
fruits and a decrease in both to or near harvest. His interpretation is
somewhat surprising, viz.: "As sugars increase, the percentage of ash
decreases, apparently indicating, as in the case of nitrogen, that there
360 BULLETIN No. 493 [October,
is no considerable intake of the mineral elements after the early stages
of fruit development." He apparently did not consider the total
amount per fruit to be of importance. Actually, Table 13 shows ap-
proximately seven times as much in the flesh at maturity as at the
beginning of the second period, nearly three times as much in the
kernel, and over four times as much in the fruit as a whole. The use
of percentages as the basis of conclusions regarding the assimilation
by the fruit of any particular constituent obviously may be very mis-
leading unless used in conjunction with the actual amounts involved.
On the percentage basis the kernel was the only part of the fruit which
showed an increased assimilation of ash during the second and third
growth periods. Only in the stone did the percentage give a fairly
accurate picture of the actual assimilation.
Ether extract. The outstanding feature of this constituent was
the decrease in both the percentage and the amount in the kernel
during the second growth period and the accelerated rate of increase
in the third period, as shown in Table 14 and Fig. 11. This is in agree-
TABLE 14. ETHER-EXTRACT CONTENT OF PEACH KERNEL
Growth
period
Date
collected
Days
after -
bloom
Percent of fresh weight
Grams per 100 fruits
Percent of dry weight
C
N
C
N
C
N
I
5-12
28
2.49
2.71
.09
.11
17.94
22.21
5-19
35
1.64
1.42
.17
.17
21.33
18.93
5-26
42
.94
.99
.21
.26
13.28
14.41
6-2
49
1.11
1.12
.47
.56
15.68
16.59
II
6-10
57
.98
.91
.56
.57
13.92
13.48
6-16
63
.94
.90
.53
.56
13.17
13.24
6-22
69
.87
.72
.49
.43
11.07
9.45
6-29
76
.64
.54
.37
.33
7.09
6.18
III
7-7
84
1.22
1.13
.70
.72
9.76
9.68
7-15
92
5.15
4.38
3.04
2.87
25.75
23.95
7-21
98
8.27
7.19
4.85
4.66
32.30
29.12
7-29
106
14.97
12.67
8.26
8.09
42.60
39.24
8-4
112
16.62
16.64
10.10
10.32
43.93
41.60
8-9
117
19.33
10.75
45.93
8-11
119
26! 16
12^22
45!59
8-15
123
21.89
12.70
46.67
ment with Hiley and Elberta in Mississippi 40 * but not with Mayflower
and Early Rose. 42 * The decrease in amount coincided with the first
macroscopic evidence of the embryo. The continued decrease until the
embryo was approaching its maximum size indicates that carbohydrates
which were formerly being stored as substances extractable by ether
were being utilized in embryo development. Additional weight is sup-
plied to this interpretation by the fact that sugars, and starch and
dextrin in the kernel showed a decrease in amount at the start of the
second period. The development of the endosperm to its maximum
size during this time must not be overlooked as an additional factor in
the utilization of food and nutrients.
1942}
DEVELOPMENT OF HALEHAVEN PEACH
361
7 14 21 28 35 42 49 57 63 69 76 84 9298 106112117123
DAYS AFTER BLOOM
FIG. 11. SEASONAL CHANGES IN AMOUNT AND PERCENTAGE OF
ETHER EXTRACT IN PEACH KERNEL, FRESH BASIS
Effects of Nitrogen Fertilization
It should be pointed out that this investigation was different in one
important respect from the usual studies of the effect of nitrogen ap-
plications. Whereas it is customary to apply nitrogen to trees of low
vigor and compare results with similar unfertilized trees, in this case
the trees at the start of the investigation were in a state of vigor that
is usually considered to be highly satisfactory for peach production.
In this investigation, therefore, the effect of the application of nitro-
362
BULLETIN No. 493
[October,
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*^-g-,- 00^0 - 31 * this acceleration in growth following
fertilization in seed-bearing fruits may be explained thus:
"We may then think of the usual fruit growth as being initiated by pollina-
tion and fertilization, which brings into the ovary a sufficient quantity of auxin
from the pollen grains and pollen tubes to start the enlargement of the 'ovary,
and continued by the additional auxin produced by the developing embryos and
seeds, which diffuses into the ovary to supply what is needed."
Considering this rapid increase in growth immediately following
fertilization, it would seem that the first growth period really starts
with fertilization. Since, however, the exact time of fertilization is not
easy to determine and probably varies with variety, season, and loca-
tion, it is usually more satisfactory to consider the time of full bloom
as the starting point of the first period.
During the first period the flesh, stone, and kernel increased
rapidly in size and in fresh and dry weights (Table 4). The relatively
high percent of dry matter in the fruit in the first four weeks of this
period (Table 7) may be associated with the hydrion concentration, as
pointed out by Caldwell, 9 * who studied a number of common fruits,
including the cherry but not the peach, and found that the young
fruits at setting and for a short period thereafter had a low hydrion
concentration and a high solids content. During this time rapid and
general cell division occurred.
Caldwell continues with the statement that this period was fol-
lowed by one of rapid increase in active acidity, rapid water absorp-
tion, and the most rapid percentage increase in weight and volume of
the fruit. The latter period of activity would coincide with the last
few weeks of the first growth period of the fruit. Consequently the
assumption seems valid that the flesh, stone, and kernel of the peach
fruit develop after bloom and fertilization in the manner characteristic
of developing tissues in general ; that is, during the first growth
period they undergo a period of cell division which is followed by
rapid cell enlargement.
Second Growth Period
The possible reason for the occurrence of this period of retarded
rate of size increase has received considerable attention from investi-
gators. During this period the flesh, stone, and kernel apparently
continue in what is usually considered to be the normal fashion for
size increase of an organ ; that is, after having passed thru the stages
of cell division and rapid cell enlargement during the first growth
period, they evidence a slower rate of size increase coincident with cell
differentiation. This differentiation is characterized by increased
thickness of cell walls in the flesh, increased thickness and lignification
in the walls of the stone cells, increased thickness in the cell walls of
the integuments, and the chemical changes already discussed.
1942] DEVELOPMENT OF HALEHAVEN PEACH 373
In this work both the stone and kernel had reached nearly maxi-
mum volume at the beginning of the second period (Table 4). This
fact, coupled with the rapid hardening of the stone in the first part of
the period, making further enlargement difficult, shows that any
retarded rate of size increase must occur largely in the flesh. Signifi-
cant increase in flesh volume occurred during this period but there
was some retardation in the rate of increase (Tables 4, 5 and 6).
The fact that the rate of dry-matter accumulation in the fruit as a
whole continued to increase, and that this was the case in previous
investigations, 39 - 40 * shows that whatever the cause for the retarded
rate of size increase in the flesh it is within the fruit itself and is not
due to such external factors as competition from shoot development,
as has been suggested. 19 *
The question naturally arises whether wall thickening and other
changes in the flesh cells can account for the retarded rate of size in-
crease in the flesh. Information is needed on the histological behavior,
during this period, of different varieties during different seasons of
ripening before this question can be entirely answered. However, the
chemical data may partly explain the developmental activity of the flesh
at this time. The rate of accumulation of reducing sugars in the flesh
at the beginning of the second period was appreciably slower than
before or after this time, while the amount of sucrose actually de-
creased (Table 9). Apparently the sugar changed to more complex
carbohydrates in the flesh or was used elsewhere in the fruit. Hemicel-
lulose increased very rapidly in the flesh from the 49th to 57th day,
the amount on the 57th day being approximately equal to that of flesh
and stone combined on the 49th day (Table 11). The rate of accumu-
lation of hemicellulose in the flesh was somewhat slower thereafter and
may not have been great enough to account for the low rate of accumu-
lation of sugars during the remainder of the period. The increase in
the starch and dextrin content during this time was not enough to be
of any importance in this connection (Table 10).
Altho the time of increase in cell-wall thickness in the flesh
coincided with the increase in the amounts of hemicellulose and dry
weight, the rate of accumulation of dry matter in the flesh decreased
after the 57th day (Table 6) rather than increasing at a consistent rate,
as might have been expected. It therefore appears that the sugars
were being used more rapidly elsewhere than in the flesh after the
57th day.
Turning now to the possibility of competition from other parts of
the fruit, let us consider the development of the stone.
The amount of dry matter in the stone increased rapidly during the
second period and slowly thereafter, decreasing during the latter part
of the final swell (Table 4). This previously was found to occur in
Hiley and Elberta. 39 ' 40 * The same trend is shown in Lilleland's apri-
374 BULLETIN No. 493 [October,
cot data. 36 * Coincident with this accumulation in dry matter was the
rapid increase in the amount of hemicellulose (Table 11) and the lig-
nification of the stone. The formation of these complex carbo-
hydrates hemicellulose and lignin would require considerable quan-
tities of simple sugars. Since the rate of accumulation of both sugars
and total dry matter in the flesh was low after the 57th day, the stone
would appear to be the dominant part of the fruit during the second
period. The fact that the stone constituted over 50 percent of the
dry weight of the fruit for approximately two weeks during this
growth period is substantiative evidence of the flesh-stone relationship
(Table 8). The same condition was shown to prevail in Hiley and
Elberta 39 - 40 * and in the apricot. 36 *
In some preliminary work with the early varieties Mayflower and
Sneed in Mississippi, 42 * it was found that the stones were not com-
pletely hard at harvest, and that the dry weight of the stone did not
equal that of the flesh at any time during the season. In these early
varieties the stone and flesh developed together to harvest, and the dry
weight of the stone never became great enough to cause more than a
short second period, or none at all, as Lilleland 37 * found in Sneed and
which also occurred elsewhere. 42 * The concomitant development of the
flesh and stone until maturity may partly account for the poor quality
of these early varieties. The continued utilization of sugars by the
stone would limit the amount available to the flesh. The data of Lott
and Ashley 41 * show that the sugar content of the ripe flesh increased
directly in proportion to the lateness of maturity of the variety. While
quality is not determined by sugar content alone, it seems to be directly
associated with it. It is possible, however, for early-ripening varieties
to have high sugar content, as shown by some of the seedlings from the
University of Illinois peach breeding plots. The fruit of some varieties
ripening approximately 100 days after bloom in 1941 had as high
sugar content as late-ripening sorts such as Elberta ; but the seasonal
development of these fruits was not followed, nor were the flesh-stone,
sugar-hemicellulose relationships investigated.
The conclusion seems plausible that the delayed rate of size in-
crease in the flesh in the second period is due largely to a combination
of cell-wall thickening with accompanying hemicellulose accumulation
in the flesh, and lignification and hemicellulose accumulation in the
stone. The relative dominance of these two phenomena will depend
upon the genetic make-up of the variety. The part played by the rapid
size increase of the endosperm and cotyledons at this time is very
difficult to determine but may be of considerable importance.
Third Growth Period
One of the most striking features of peach fruit development is the
rapid increase in size and dry weight during the third growth period.
1942] DEVELOPMENT OF HALEHAVEN PEACH 375
It has been shown that the stone decreased slightly in size during this
time. The size increase which occurred was therefore in the flesh. The
increase in dry weight was also in the flesh, because the decreasing dry
weight of the stone offset the dry-weight increase in the kernel. The
data already presented show that the increased dry weight of the flesh
was due primarily to the rapid increase in sugars. Consequently any
consideration of the reason for this final swell centers largely upon the
source of supply of the sugars during this period.
That there is a very noticeable increase in size during this time
has been mentioned by nearly all investigators of the subject (see
References 2, 5, 6, 13, 18, 22, and others), but no attention seems to
have been given to any aspect other than observable size increase. A
further consideration seems desirable.
It is commonly known that the volume of the flesh increases two
to four or more times during this period, but there does not seem to
be any definite information concerning the percentage of this increase
that is due to cell enlargement and the percentage due to increase in
volume of intercellular spaces. That the increase in volume is due
primarily to cell enlargement is indicated by the report of Addoms 1 *
that the intercellular spaces between the flesh cells of Elberta remained
relatively small during the maturation of the fruit. That there may be
considerable difference between peach varieties in this respect is indi-
cated by the fact that in some varieties of the sour cherry there are no
intercellular spaces in the flesh at maturity. 25 ' 71 *
The greater part of the increase in flesh volume during the third
period would thus seem to be due to increase in cell size. Such in-
creases would be accompanied by large increases in the surface area
of the individual cells, which would necessitate a decrease in cell-wall
thickness or a rapid increase in the deposition of cell-wall materials.
It is therefore obvious that very erroneous conclusions might be
reached concerning the trend of a cell-wall constituent if only the
change in thickness was considered. Definite data on this point are
necessary before the final swell of the peach fruit can be thoroly
understood.
The next point to consider is the possibility of the transformation
of more complex carbohydrates in the flesh to sugar during the third
growth period. That the quantity of starch and dextrin was never
great enough to be of any consequence in this respect is shown by the
data in Table 10. Hemicellulose showed (Table 11) a decrease only in
the last sample, and this decrease was not great enough to be of any
significance in relation to the increase in the amount of sugar. Further-
more there is no assurance that any of this hemicellulose was hydro-
lyzed to sugar. The data of Mrak et a/ 43 * show a fairly high percent-
age of lignin in dried prunes. The same condition may occur in
peaches, since positive microchemical tests for lignin were obtained in
the vascular bundles in the last few samples. Some hemicellulose may
376 BULLETIN No. 493 [October,
have been converted to lignin ; but according to the view of Ehrlich, 26 *
the lignin would more likely arise from pectin, but hemicellulose as
here determined would include at least a part of the pectin.
The relationships of the more complex carbohydrates in the peach
during ripening is somewhat unsettled. Nightingale 51 * reported a de-
crease in protopectin, hemicellulose, and cellulose during the ripening
of the peach. Since he presented the data only on the percentage basis,
it is impossible to determine whether the actual amounts decreased. If,
however, one assumes that the normal final swell occurred in the fruits
which he examined, his data indicate that there was no decrease in
amounts, with the exception of protopectin in the last sample. Apple-
man and Conrad 3 * concluded that the transformation of protopectin
to soluble pectin was the chief process responsible for the softening of
peaches.
Obviously there is need for further study of the ripening processes,
including a consideration of the cell-wall changes, and the expression of
results in amounts per fruit. The conclusion seems inevitable that the
large increases in sugar in the third growth period of the flesh of the
peach cannot come from other forms of carbohydrates in the flesh.
The decrease in the amount of hemicellulose in the stone during
the time that the sugar content of the flesh was increasing most rapidly
indicates hydrolysis and translocation, since all the other analyzed
carbohydrates in the stone decreased at this time. Some of the hemi-
cellulose may have been transferred to the kernel for storage, but only
a small part of the decrease could be accounted for by increases in the
kernel. The amount of the decrease of hemicellulose in the stone was
small in comparison with the sugar increase in the flesh, but it may
have been the source of a part of the sugars. This condition might be
interpreted as a hemicellulose-sugar relationship in accordance with
Murneek's conception of hemicellulose as a storage carbohydrate. 47 *
Definite conclusions on this subject cannot be drawn without a more
detailed separation of the acid hydrolyzable fraction here designated
as hemicellulose. Nevertheless it appears that a portion of the materials
included in the hemicellulose determination did act as a reserve sub-
stance that was translocated from the stone during the final swell.
This condition also occurred in Hiley and Elberta. 39 - 40 * The fact that
hemicellulose did not seem to act as a reserve substance in the flesh
does not preclude the possibility of such a situation in the stone. Aside
from the relative activity of these two organs during the third growth
period, the probable difference in the nature of their hemicelluloses may
play a part. According to Buston, 8 *
" . . . . lignified tissues are characterized by the presence of xylan and
allied hexo-pentosans of the same series (glucosan-glycuronic anhydride-xylan),
while in nonlignified material galacto-arabans constitute the main bulk of the
hemicelluloses."
1942] DEVELOPMENT OF HALEHAVEN PEACH 377
Because the decrease in hemicellulose in the stone could at the most
account for only a small part of the sugar increase in the flesh during
the final swell, and the added fact that in some early-ripening varieties
the hemicellulose content of the stone has been found to increase until
flesh maturity, 42 * most of the sugar must come from the tree. Davis 17 *
found that in the Sugar prune the increase in sugars during the final
swell was accompanied by a corresponding depletion of starch in the
branches back of the spur. This phase of the problem has not been
investigated in detail in the peach. Tottingham 65 * considers that
hemicellulose is a reserve material in the peach, but his results would
not necessarily be applicable here since he did not state whether he
used bearing trees.
The fact that during the third period the C leaves decreased in dry
weight (Table 19) suggests the possibility that not only were all the
products of photosynthesis being translocated into the fruit but some
of the materials that had been temporarily stored in the leaves were
also being translocated. That such a condition would be more marked
in trees with a nitrogen deficiency is indicated by the fact that the N
leaves did not similarly decrease in dry weight. The increased chloro-
phyl content from nitrogen fertilization and the greater size of the N
leaves apparently made possible a rate of carbohydrate manufacture
in excess of the assimilable demands of the developing fruits.
In studying the effect of fruit production on tree growth in several
fruit species, including the peach, Chandler 11 * points out the possibility
of a greater rate of photosynthesis on the bearing trees, due to the
removal of the products of photosynthesis to the fruit. This suggests
the possibility of a greater rate of photosynthesis during the final swell
because of the rapid removal of the products of photosynthesis to the
fruit.
Obviously the information is too meager to permit definite conclu-
sions concerning the cause of the rapid increase in sugars during the
final swell. A more complete chemical study, more detailed investiga-
tion concerning the relationship between fruit development and the
growth of all parts of the tree, and a study of the relationship be-
tween fruit growth and leaf activity are suggested as sources of addi-
tional information.
The effect of the kernel upon the growth of the flesh and stone
should not be overlooked. Even tho the kernel is not important on a
mass basis, it may nevertheless play a very important part in the
development of the stone and flesh. It has been definitely established
that the act of fertilization in some way causes a rapid rise in the
growth rate. 45 - 49> 50 * It has been shown by Tukey 69 * that in the Prunus
species the side of the fruit to which the functional ovule is attached
develops more rapidly than the other, resulting in an asymmetric fruit.
When both ovules developed, the fruit was symmetrical. It is well
378 BULLETIN No. 493 [October,
known that fertilization is usually necessary for normal fruit develop-
ment in the common deciduous tree fruits.
The question of the possible effect upon fruit development of the
growth of the kernel after fertilization is unsettled. In a study of
the effect of branch ringing and defoliation on the development of the
embryo of the peach, 72 * Tukey concluded:
". . . . it is abortion of the embryo which induces early-ripening of the
fruit, and not the reverse .... when the supply of materials to the embryo
from outside the fruit is limited, as by ringing and defoliation, the embryo
continues to increase in size and storage materials continue to be mobilized."
It was found by Lott and Ashley 41> 42 * in Mississippi that the early
peach varieties Mayflower, Sneed, and Early Rose did not produce
truly abortive ovules except in a small percentage of the fruits. The
kernels were still plump at harvest, but the cotyledons had reached
only about half the length of the nucellus. A number of seedlings in
the University of Illinois peach-breeding plots which ripened fruit in
approximately 100 days after bloom in 1941 had kernels in which the
cotyledons filled the integuments except for a very thin layer of endo-
sperm, and the outer integument was light brown, indicating an ap-
proach to maturity. Consequently there would seem to be no definite
cause-and-effect relationship between kernel development and the
initiation of the third growth period in early-ripening varieties of the
peach. Furthermore there is considerable evidence to indicate that in
the peach the development of the kernels to maturity is not necessary
for the production of normal fruits. Havis 33 * has recently reported
the effects on peach fruit development of the death of the ovules as
the result of frost three weeks after bloom. He found that the fruits
with dead ovules developed in essentially the same manner as those
with normal ovules. The writer has frequently observed peach fruits
with aborted ovules in which the development of flesh and stone was
approximately the same as that of fruits with normal ovules.
If the kernel does affect the development of the flesh, this effect
probably occurs during the first three or four weeks after bloom. It
is quite possible that a metabolic status that would extend to ma-
turity could be established in the fruit during that time. This could
occur on the basis of auxin brought into the ovule in the pollen tubes
and that produced by the developing embryo, as conceived by
Gustafson. 31 *
Another viewpoint that might be entertained is that either or both
the kind or amount of growth-regulating material is such in late-ripen-
ing varieties that the kernel is dominant over the flesh until sufficient
time has elapsed to make possible the subsequent normal development
of the kernel; whereas the setup in early varieties is such that the
flesh dominates the kernel, with the result that the flesh completes its
development while the kernel is still in a relatively undeveloped condi-
1942} DEVELOPMENT OF HALEHAVEN PEACH 379
tion. A further possibility seems to be the presence, in different pro-
portions in different varieties, of separate growth-regulating substances
for the flesh and the kernel. The development of the stone could also
be included in such an hypothesis. In any event the fact must not be
lost sight of that the differential development of flesh, stone, and
kernel in varieties of the peach is governed by their genetic make-up.
Changes in Stone and Kernel
The data obtained in this investigation and the facts presented in
the preceding discussion show that the ordinary conception of the three
growth periods fails to express all of the growth activities of the fruit.
Altho this concept is useful because it is easily understood and it does
include fairly accurately the changes that occur in the size manifesta-
tion of growth, other growth phenomena should be considered.
Actually the three growth periods usually described by investiga-
tors explain primarily only the size increase in the flesh. The present
study, together with previous work by the author, adds the following
information concerning the development of the stone and the kernel:
The stone: Period 1. Increases rapidly in size to approximately a
maximum, due to cell division and cell enlargement. Increase continues
from bloom until stone is hard enough to cut away with a knife.
Period 2. Slow increase in size. Stone hardens rapidly and in-
creases rapidly in dry matter. Little or no cell division takes place.
Period continues until harvest in early varieties, but terminates before
harvest in late varieties.
Period 3. In late varieties only. Stone is stationary or decreasing
in size and in dry-matter content. Period continues until harvest.
The kernel: Period 1. Nucellus and integuments increase rapidly
in size to nearly a maximum. No macroscopic evidence of endosperm
or embryo. This period coincides with Period 1 of flesh and stone.
Period 2. Slow increase in size of nucellus and integuments. Endo-
sperm and embryo are macroscopically evident; rate of size increase
is usually correlated with lateness of ripening. Period continues until
harvest in early varieties but ends with attainment of maximum embryo
size in late varieties.
Period 3. In the late varieties only. Dry matter increases rapidly,
particularly the ether extract.
The terms early and late as used here will apply to such varieties
as Mayflower, Sneed, and Early Rose for early varieties and Elberta
as a late variety. The intermediate varieties probably will, in general,
exhibit the characters of the group they most closely approach in time
of ripening. Exceptions may well be found as the number of varieties
examined increases.
380 BULLETIN No. 493 [October,
SUMMARY AND CONCLUSIONS
The seasonal development of the fruit on two six-year-old Hale-
haven peach trees was observed from the time the trees were in full
bloom to the time when the flesh became soft ripe. A vigor differential
was established between the two trees by two 5-pound applications of
nitrate of soda to one of them the first, 17 days before full bloom,
and the second just as the stones began to harden 51 days after bloom.
Samples were collected at weekly intervals and determinations were
made of the diameter, volume, fresh weight, and dry weight of the
entire fruit, the flesh, the stone, and the kernel. The flesh, stone, and
kernel were analyzed for the content of the following constituents:
reducing sugars, sucrose, starch and dextrin, hemicellulose, total nitro-
gen, ash, and ether extract.
When growth of fruit was measured by increase in its diameter,
volume, or fresh weight, three periods of development were evident:
1. The first growth period, which ended when the stone was
first hard enough to separate from the flesh 57 days after bloom.
This period was characterized by rapid increase in size and fresh
weight of flesh, stone, and kernel ; by attainment of nearly maximum
size of stone and kernel ; by absence of macroscopic evidence of
growth in endosperm and embryo until near the end of the period ; and
by an increase in the amount of each of the determined constituents.
2. The second growth period, which ended approximately 76
days after bloom. This period was characterized by a slow rate of
increase in size of flesh, stone, and kernel ; by a reduced rate of dry-
matter accumulation in the flesh and kernel, but by the most rapid rate
of increase in the stone ; by the development of the endosperm and
embryo to approximately maximum size ; by a reduced rate of accumu-
lation of all constituents in the flesh and the kernel, but by the most
rapid increase in lignification and hemicellulose content in the stone.
3. The third growth period, extending to the soft ripe condition
of the flesh 117 days after bloom in the check fruits and 123 days after
bloom in the nitrated fruits. This period was characterized by an
accelerating increase in size and dry matter of the flesh ; by a decrease
in volume and dry matter of the stone during the latter half of the
period; by a decrease in volume but the most rapid increase in dry
matter of the kernel; by an increase in the amount of all determined
constituents of the flesh, with a particularly rapid increase in sucrose
during the last 11 days; by a decrease in the amount of all constitu-
ents of the stone ; and by an increase in the amount of all constitu-
ents of the kernel except starch and dextrin, which decreased. Ninety-
four percent of the total amount of ether extract in the kernel
accumulated during the third period.
The transition from one period to the next was not abrupt ; hence
only approximate dates can be given for the duration of each period.
1942] DEVELOPMENT OF HALEHAVEN PEACH 381
When dry-weight increase was used as the measure of growth, no
clearly defined second period was evident, the rate of increase in each
sampling interval being as great as that in the preceding interval. The
rate of increase was accelerated, however, during the last three weeks
before harvest.
The rate of development was almost parallel between the fruits of
the two treatments, regardless of method of measurement, until about
three weeks before harvest, when the check fruits developed more
rapidly for a few days and then were surpassed by the fertilized fruits.
The principal effects of the nitrogen fertilization were:
In the tree: greater yield, more and longer shoots ; larger, heavier
and greener leaves ; and more fruit buds for the succeeding year.
In the fruit: greater size, six days later ripening, slightly less in-
tense color, no detectable difference in quality, and a greater ratio of
flesh to stone on both the fresh-weight and the dry-weight basis.
In the flesh: higher percentages of starch and dextrin, ash, and
nitrogen ; but lower percentages of reducing sugars and hemicellulose.
In the stone: greater size and weight, higher percentages of nitro-
gen, hemicellulose, starch and dextrin ; but lower percentages of
sugars and ash.
In the kernel: greater dry weight, and greater percentages of all
constituents except reducing sugars.
The fertilizing of peach trees with liberal quantities of a readily
available nitrogenous fertilizer would thus seem highly desirable
under conditions similar to those of this investigation, resulting in
more vigorous vegetative growth, the formation of more fruit buds,
and a greater yield of larger fruit as attractive in color and as high
in quality as that from trees not so fertilized.
The necessity for giving detailed attention to the separate parts
of the fruit in any study of the physiological development of the peach
as a whole is emphasized by the data, which reveal some of the growth
relationships existing between the flesh, stone, and kernel. Still
further separation of the fruit parts, such as that of the kernel into
integuments, endosperm, and embryo, and the development of more
precise methods of analysis are necessary in order to add to the exist-
ing knowledge of the details of the growth processes.
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