in;'. f 
 
 
 Issued September 10, 191'i. 
 
 HAWAII AGRICULTURAL EXPERIMENT STATION, 
 
 E. V. WILCOX, Special Agent in Charge. 
 
 Bulletin No. 28. 
 
 THE EFFECT OF MANGANESE ON 
 PINEAPPLE PLANTS 
 
 AND 
 
 THE RIPENING OF THE 
 
 PINEAPPLE FRUITSl 
 
 BY 
 
 E. V. WILCOX, 
 
 Special Agent in Charge 
 
 AND 
 
 W. P. KELLEY, 
 
 Chemist. 
 
 UNDER THE SUPERVISION' OF 
 OFFICE OF EXPERIMENT STA 
 
 U. 8. DEPARTMENT OF AGRICTJLTU 
 
 
 WASHINGTON: 
 GOVERNMENT PRINTING OFFICE. 
 
 i:M2. 
 
Issued September 10, 1912. 
 
 HAWAII AGRICULTURAL EXPERIMENT STATION, 
 
 E. V. WILCOX, Special Agent in Charge. 
 
 Bulletin No. 28. 
 
 THE EFFECT OF MANGANESE ON 
 PINEAPPLE PLANTS 
 
 AND 
 
 THE RIPENING OF THE 
 PINEAPPLE FRUIT. 
 
 BY 
 
 E. V. WILCOX, 
 
 Special Agent in Charge, 
 
 AND 
 
 W. P. KELLEY, 
 
 Chemist. 
 
 UNDER THE SUPERVISION OF 
 OFFICE OF EXPERIMENT STATIONS, 
 
 U. 9. DEPARTMENT OF AGRICULTURE. 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 
 1912. 
 
HAWAII AGRICULTURAL EXPERIMENT STATION, HONOLULU. 
 
 [Under the supervision of A. C. True, Director of the Office of Experiment 
 Stations, United States Department of Agriculture.] 
 
 Walter H. Evans, Chief of Division of Insular Stations, Office of Experiment 
 
 Stations. 
 
 STATION STAFF. 
 
 E. V. Wilcox, Special Agent in Charge. 
 J. Edgar Higgins, Horticulturist. 
 W. P. Kellev, Chemist. 
 
 C. K. McClelland, Agronomist. 
 
 D. T. Fullaway, Entomologist. 
 
 W. T. McGeorge, Assistant Chemist. 
 Alice R. Thompson, Assistant Chemist. 
 C. J. Hunn, Assistant Horticulturist. 
 V. S. Holt, Assistant in Horticulture. 
 C. A. Sahr, Assistant in Agronomy. 
 
 (2) 
 [Bull. 28] 
 
LETTER OF TRANSMITTAL 
 
 Honolulu, Hawaii, May 1, 1912. 
 Sir: I have the honor to submit herewith and recommend for 
 publication, as Bulletin Xo. 28 of the Hawaii Agricultural Experi- 
 ment Station, a paper on the Effect of Manganese on Pineapple 
 Plants, and the Ripening of Pineapple Fruit, prepared jointly by 
 myself and Mr. W. P. Kelley, chemist. Chemical investigation on 
 the cause of yellowing of pineapples on certain soils and on the 
 ripening of the pineapple fruits has been carried on for the past 
 three years, and some of the important results of this investigation 
 are stated in this paper. A microscopic study was made of all the 
 different parts of pineapples for the purpose of learning the struc- 
 tural changes produced by the presence of large quantities of man- 
 ganese in the soil and the morphological changes which occur in the 
 ripening of the fruit. The anatomical and chemical findings are in 
 rather striking harmony. The practical bearing of these investiga- 
 tions should be of importance in the further development of the 
 pineapple industry. 
 
 Respectfully, E. V. Wilcox, 
 
 Special Agent in Charge. 
 Dr. A. C. True, 
 
 Director Office of Experiment Stations, 
 
 V. S. Department of Agriculture, 'Washington, D. C. 
 
 Publication recommended. 
 A. C. True, Director. 
 
 Publication authorized. 
 
 Ja^ies "Wilson, Secretary of Agriculture. 
 
 (3) 
 
 [Bull. 28] 
 
CONTENTS. 
 
 Page. 
 
 The effect of manganese on pineapple plants 7 
 
 Introduction 7 
 
 Pineapple roots 7 
 
 Leaves 8 
 
 Oxalate of lime 11 
 
 Other visible effects of manganese 11 
 
 The chemistry of the pineapple plant 12 
 
 The composition of the pineapple plant as affected by manganese 13 
 
 The ripening of the pineapple fruit 14 
 
 The chemistry of ripening 16 
 
 Summary 19 
 
 ILLUSTRATIONS. 
 
 Page. 
 
 Plate I. Structure of pineapple leaf showing effect of manganese 8 
 
 II . Cells from pineapple leaves and fruits 8 
 
 (5) 
 [Bull. 28] 
 
THE EFFECT OF MANGANESE ON PINEAPPLE PLANTS, AND 
 THE RIPENING OF THE PINEAPPLE FRUIT. 
 
 THE EFFECT OF MANGANESE ON PINEAPPLE PLANTS. 
 INTRODUCTION. 
 
 The pineapple belongs to the family Bromeliacea?, several species 
 of which are of epiphytic habit. With the exception of the black 
 moss of the South which, as its name indicates, has a moss-like habit 
 of growth and small terete branches, the members of this family 
 which we have been able to examine show very similar structure and 
 arrangement of the cellular tissue of the leaves. The pineapple pre- 
 sents certain peculiar habits of growth which constantly remind one 
 of the fact that it belongs to a family of plants in which a number of 
 epiphytic species occur. The family as a whole occurs principally in 
 tropical and subtropical climates and exhibits a power of adaptation 
 to a wide range of conditions of soil and rainfall. 
 
 The studies reported in this bulletin were undertaken jointly as a 
 continuation of the work reported by this station regarding the effect 
 of manganese on pineapples, and also regarding some of the points 
 which have been observed in the chemical composition of pineapple 
 fruits in different stages of development. 1 It will be noticed in study- 
 ing the results which we have obtained that the anatomical and 
 chemical findings are in remarkable harmony and that they mutually 
 assist in explaining each other. 
 
 PINEAPPLE ROOTS. 
 
 One of the points which is likely to appear most striking in the 
 study of pineapples in the field is the great variation in the root 
 structures. Under favorable conditions the roots may be several feet 
 in length and may quite fully occupy the soil in all directions from 
 the base of the plant. In pulling up apparently vigorous plants, 
 however, many will be found to have almost no root system, although 
 the aerial portion of the plant appears to be as vigorous as those 
 which possess a well-developed set of roots. Moreover, it is also a 
 striking fact that even on many of the most healthy plants the roots 
 may be nearly all dead and in process of decay, with only here and 
 
 1 Hawaii gta. Bui. 26 ; Press Bui. 23^ Rpt. 1909, pp. 58-63; Rpt. 1910, pp. 41^3, 45-50. 
 
 (7) 
 
 [Bull. 28] 
 
8 
 
 there a living root covered near its growing tip with root hairs. In 
 the zone of the root where the root hairs occur these structures are 
 remarkably abundant, the large majority of the epidermal cells of 
 the root being developed into hair structures. It is a difficult matter, 
 therefore, to wash the soil away from these portions of the roots 
 without tearing off the root hairs. It is impossible to determine with 
 certainty the causes which bring about the great variation in the 
 length and number of living roots on plants which seem to be quite 
 vigorous and on normal soils. The proper development of the root 
 system, however, seems to depend largely upon suitable physical con- 
 ditions in the soil. Where drainage is poor and where the soil 
 becomes packed or puddled below the depth of cultivation, it is 
 impossible for the roots to penetrate and develop as they otherwise 
 might do. 
 
 In general it may be said that the root system of pineapples grow- 
 ing on highly manga niferous soils is rather less extensive than that 
 observed on normal soils. The number of small fibrous branches on 
 the main roots is much reduced in manganiferous soils. One of the 
 most striking effects of a high percentage of manganese in the soil is 
 observed in the root tips, which quite generally show rounded swollen 
 ends rather than the pointed tips with rootcaps, such as occur in nor- 
 mal soils. These swollen root tips are almost invariably dead or 
 dying and usually are found in process of decay. It is obvious that 
 they have in all cases ceased growing. In fact, growth is impossible 
 after the swelling occurs, since the roots are then unable to penetrate 
 farther into the soil. In the woody tissue and in the cells imme- 
 diately under the epidermis of roots growing in manganiferous soil 
 there is a slightly greater tendency toward browning of the cell walls 
 than is the case in normal soils. 
 
 LEAVES. 
 
 The leaves of the pineapple and other members of the same family 
 with similar habits of growth are attached to the short stems of the 
 plant close together and spread at an angle of 45°, more or less, from 
 the axis of the plant. The edges of the leaves are curved upward, 
 so that a cross section of a leaf is approximately a semicircle. 
 
 In the normal pineapple plant the upper surface of the leaf shows 
 a conspicuous red color, which is confined to the central third of the 
 leaf surface. The upward curving of the edges of the leaf naturally 
 divides the upper surface of the leaf into three nearly equal portions, 
 two being upright, one on either side, and the third portion lying at 
 the bottom of the trough. This central or lower third receives the 
 sunlight to a much greater degree than the sides of the leaf, and the 
 development of a red coloring matter in the lower third seems to be 
 
 [Bull. 23] 
 
jl. 28, Hawaii Agr. Expt. Station. 
 
 Pl-ATF I. 
 
 J. 
 
 ■v»fe. 
 
 
 
 5a rH? K^I/iMK!**' 
 
 I 
 
 ti 
 
 I i* 
 
 c 
 
 *'■■ 
 
 
 
 
 Str_ f, showing Effect of Manganese. 
 
 - 
 
Jul. 28, Hawaii Agr. Ex; I 
 
 Plate 
 
 Cells ff ple leaves and Fru 
 
 ..in highlj n 
 
 1 rrom pulp of ripe pineapple fruit. 
 
directly connected with this fact. It apparently forms a screen 
 which protects the underlying chlorophyll from the intense action of 
 the tropical sun. This hypothesis is home out by the arrangement of 
 the chlorophyll in the leaves of pineapples and related species of the 
 same family, as will be presently shown. 
 
 One of the peculiar features of the pineapple leaf is the apparent 
 absence oi' stomata. Hundreds of sections were made from pine- 
 apple leaves and examined under the microscope, and portions of the 
 epidermis of the upper and under sides of the leaves were carefully 
 examined without finding any true stomata. There are in some 
 parts of the leaves pits in the epidermis in which much-branched 
 scale-like trichomes are attached. These structures are particularly 
 numerous on the under side of the leaf near the base. The trichomes 
 in question are supposed to be connected with the absorption o| 
 water. 
 
 Running through the leaves parallel to the strands of fibrovascular 
 tissue are strands of branched or stellate cells, which show large 
 intercellular spaces between their branches. These strands lie directly 
 over the pits in the epidermis of the lower side of the leaf and 
 seem to be connected with transpiration and the absorption of gases. 
 It would appear that the respiratory system of the pineapple is 
 abortive, for when the leaves of Bromelia are studied the develop- 
 ment of the strands of branched cells and the stomata is very con- 
 spicuous. In this genus there are numerous small tubular masses 
 of branched cells which extend from the general strands of this 
 tissue to the epidermis of the lower side of the leaf and are directly 
 connected with the stomata, which are arranged very close together 
 in parallel furrows which alternate with ridges on the lower surface 
 of the leaf. In the pineapple, on the other hand, there are no spe* 
 cially modified cells connecting the strands of branched cells with 
 the epidermis. In Greigia, another genus of this family, no branched 
 cells occur in the leaves. The chlorophyll-bearing tissue in this 
 genus is a very thin layer on the lower surface of the leaf, and the 
 respiratory processes appear to go on without the assistance of the 
 stellate cells. 
 
 In cross sections of normal pineapple leaves it is at once noticed 
 that from one-fifth to two-fifths of the thickness of the leaf on the? 
 upper side is composed of colorless tissue containing cell sap and 
 practically no other cell contents. This tissue, with the exception 
 of one or two layers of cells next to the epidermis, is concerned in 
 the movement and. transportation of cell sap. Below the region of 
 the palisade cells lies the spongy parenchyma, which occupies about 
 three-fifths of the thickness of the leaf of the pineapple, and through 
 which the strands of fihrovascular tissue run lengthwise of the leaf, 
 m°— BnlL 2&— 12 2 
 
10 
 
 The chlorophyll in the leaves of normal pineapples is nearly all con- 
 tained in this spongy parenchyma and is therefore protected from 
 the direct sunlight by means of a layer of cells next to the epidermis 
 containing a red coloring matter and by a layer of palisade tissue 
 three or four cells deep. In Bromelia the palisade cells occupy 
 about three-fifths of the thickness of the leaf and in Greigia about 
 four-fifths of the leaf. The layer of delicate palisade cells, showing 
 no cell contents except cell sap, makes it a rather difficult matter to 
 obtain good free-hand sections without injury or disarrangement 
 of the cell structure. The arrangement of the cell structures in the 
 cross section of a normal pineapple leaf is shown in Plate I, A. 
 
 In contrast with the anatomical features of the normal pineapple 
 leaf attention is called to Plate I, B, which shows a corresponding 
 section of a leaf of a pineapple grown on a highly manganiferous 
 soil. This figure shows the destruction which has taken place in the 
 chlorophyll and the protoplasmic bodies in, general. A few small 
 green granules are observed here and there, but the most of the 
 chlorophyll bodies have been disintegrated and have disappeared or 
 at least lost their green coloring-matter. In a few instances it will be 
 observed that the protoplasmic bodies have become discolored with a 
 more or less pronounced brown. The arrangement of the chloroplryll 
 bodies in the normal leaf is shown under higher magnification in the 
 cells of spongy parenchyma in Plate I, C. If the condition shown in 
 that figure is compared with A, B, and C of Plate II the stages in the 
 disintegration and destruction of the chloroplasts will be readily seen. 
 At first the chloroplasts begin to lose the regular form, and the green 
 coloring matter is diffused through the protoplasmic substance of the 
 cell, while the protoplasmic bodies disintegrate into smaller granules 
 and remain separate or are grouped together in irregular masses show- 
 ing a paler and paler green as the effect of the manganese continues. 
 In the final stages of the yellowing of the leaf every trace of green 
 matter has disappeared and only small irregular granules of pale 
 protoplasm are to be seen in the cells which previously carried normal 
 chloroplasts. The conspicuous feature of the effect of manganese 
 upon the growth of pineapple plants is the pronounced and peculiar 
 yellow color of the leaves. Under the microscope the cause for this 
 yellowing is found in the loss of the green coloring matter and in the 
 slight tendencv toward the vellowing of the cell wall and disin- 
 tegrated protoplasmic substance under the influence of manganese. 
 
 In the normal leaf an ordinary iodin test shows the presence of 
 starch granules in the protoplasmic bodies. Simultaneous with the 
 etiolation of the chloroplasts the iodin fails to show the presence of 
 starch. In the later stages of the yellowing of the leaves only occa- 
 sional granules of starch are to be found here and there in the dis- 
 
 [Bull. 28] 
 
11 
 
 integrated cell contents of the spongy parenchyma. The amount 
 of starch which is stored up in the stem of the pineapple, however, 
 is still almost, as gre^t in plants growing on manganese soils as in 
 normal plants. 
 
 The peculiar distribution of the chlorophyll exclusively at the 
 lower side of the leaf seems to be characteristic of the family Brome- 
 liaceaN so far as we have had opportunity to observe. At any rate 
 the chlorophyll is regularly distributed throughout the thickness of 
 the leaf or as densely near the upper surface as near the lower sur- 
 face in leaves of mango, Croton, Sapium, papaya, Monstera, sisal, 
 Sansevieria, oleander, Calophyllum, Eucalyptus, Chrysophyllum, 
 Agave americana, canna, Peireskia, banana, prickly pear, CordyUne 
 termhialis, and vanilla. In none of these plants, except a few in 
 the early stages of growth of the leaves, is there any pronounced de- 
 velopment of red coloring matter, which might serve to protect the 
 chlorophyll, nor m any of the plants mentioned is the chlorophyll 
 restricted to the lower surface of the leaf. It would seem from the 
 observations which we have made that the pineapple and closely 
 related species of the same family are particularly sensitive plants in 
 this respect. The unusually rapid destruction of the chlorophyll 
 bodies and the yellowing of the leaves of pineapples, as compared 
 with other cultivated plants on manganese soils, also favors this view. 
 
 OXALATE OF LI3IE. 
 
 Chemical analyses Ojl various parts of the pineapple plant show 
 that there is a much larger quantity of lime in plants growing on 
 manganese soils than in those on normal soils. This finding is partly 
 explained and further confirmed by the fact that when examined 
 under the microscope all parts of such plants are found to contain 
 enormously large numbers of the needlelike crystals of oxalate of 
 lime. These crystals are especially numerous in the fruits, but are 
 also relatively much more numerous in the leaves of pineapples 
 turned yellow from the effects of manganese than in leaves of the 
 normal green plants. 
 
 OTHER VISIBLE EFFECTS OF MANGANESE. 
 
 However the effect of manganese on pineapples and other plants 
 may be explained, it seems not to be entirely due to the increased 
 amount of manganese absorbed by pineapples on highly manganifer- 
 ous soils, for the amount of increase of manganese in the ash is not 
 sufficiently large to permit such a view to be held. A thorough 
 search was made for the possible visible appearance of manganese in 
 plants other than pineapples. Minute concretions of manganese were 
 found on the ducts and sieve tubes in the roots of mango and straw- 
 berry. These concretions were readily dissolved by hydrochloric 
 
 [Bull. 28] 
 
12 
 
 acid. The presence of citric acid in pineapples would tend to keep 
 the manganese in solution, and this may explain the fact that no 
 visible deposits of manganese could be found in pineapples. 
 
 In addition to the brown color of the protoplasm referred to above, 
 it should be mentioned that the roots of pineapples growing on 
 highly manganiferous soils show a darker brown color than in normal 
 plants and that distinct brown patches appear on the upper surface 
 of the leaves of plants during the later' stages of yellowing. These 
 brown areas may be sunken or elevated and the roughness of the 
 surface seems to be due to the death of the tissue underneath and the 
 consequent shrinking, thus throwing the surface into folds. The 
 brown patches are perhaps the results of sun scald, which apparently 
 takes place more rapidly after the living tissues have been injured by 
 manganese and the regulatory apparatus is thereby destroyed. 
 
 THE CHEMISTRY OF THE PINEAPPLE PLANT. 
 
 The development of a yellow color in the leaves of pineapples on 
 certain soils of Oahu has become a matter of common observation. 
 Investigations into the cause of this phenomenon have resulted in 
 establishing a direct relationship between the occurrence of manga- 
 nese in the soil and the yellowing of the pineapples. In 1909, 1 
 from a preliminary investigation, it was pointed out that the degree 
 of yellowing is directly proportional to the amount of manganese in 
 the soil, and that the manganese exists in the soil in a state of higher 
 oxids, from which forms it readily becomes available to the roots 
 of plants. It was further shown by the use of the Dyer method that 
 the manganese is quite soluble. Subsequently it has been pointed 
 out that the solubility of manganese in various dilute organic acids 2 
 is very pronounced, and that its solubility in distilled water in some 
 instances is greater than that of any other element in the soil. It 
 was further pointed out that the general metabolism of the pineapple, 
 when grown on manganiferous soils, is considerably modified. In 
 order to throw more light on this question, an extensive study of the 
 chemistry of the pineapple plant has been undertaken in conjunction 
 with the anatomical and physiological investigations. 
 
 The results obtained, it is believed, will enable a proper under- 
 standing of certain peculiarities already mentioned and afford a 
 more exact chemical basis for a comprehension' of the physiology of 
 the plant, and also furnish some explanation for the peculiarities 
 attending the presence of large amounts of manganese in the soil. 
 In this study the mineral constituents of the several parts of the 
 plant have been determined. 
 
 1 Hawaii Sta. Press Bui. 23; Jour. Indus, and Engin. Chem., 1 (1909), pp. 533-538. 
 
 2 Hawaii Sta. Rpt. 1909, p. 63. 
 
 [Bull. 28] 
 
13 
 
 THE COMPOSITION OF THE PINEAPPLE PLANT AS AFFECTED BY 
 
 MANGANESE. 
 
 Ill this investigation a number of representative plants from 
 highly manganiferous soil, on the one hand, and from normal soil, 
 on the other, were separated into leaves and stalk, and after becom- 
 ing thoroughly air dried were subjected to analysis. The ash was 
 determined by incinerating over a free flame at a temperature well 
 below redness, then leaching with distilled water, according to the 
 optional method of the Association of Official Agricultural Chemists 
 for the determination of ash in plants. 1 The several mineral con- 
 stituents were determined in samples of the ash thus obtained. It 
 should be mentioned in this connection that the percentages of sul- 
 phur, chlorin, and possibly phosphorus pentoxid, should not be con- 
 sidered as absolute, for the reason that partial volatilization may 
 have taken place. In the case of phosphorus pentoxid, a number of 
 determinations were made by the use of wet methods, and results 
 closely agreeing with those secured from the ash were obtained, so 
 that fair accuracy is believed to have been obtained. In any event, 
 the results are comparable among themselves, and since it is for this 
 purpose that they are submitted, their value is not greatly impaired. 
 
 The composition of the ash of leaves and stalk from the two classes 
 of soil is recorded in the following table : 2 
 
 Composition of pineapple leaves and stalk. 
 
 Leaves. 
 
 Stalk. 
 
 5 months 
 old from 
 manganif- 
 erous soil. 
 
 5 months 
 
 old from 
 
 normal 
 
 soil. 
 
 18 months 
 old from 
 manganif- 
 erous soil. 
 
 18 months 
 
 old from 
 
 normal 
 
 soil. 
 
 5 months 
 old from 
 manganif- 
 erous soil. 
 
 5 months 
 
 old from 
 
 normal 
 
 soil. 
 
 18 months 
 old from 
 manganif- 
 erous soil. 
 
 Per cent. 
 7.14 
 
 Per cent. 
 7.98 
 
 Per cent. 
 6.24 
 
 Per cent. 
 8.86 
 
 Per cent. 
 5.12 
 
 Per cent. 
 7.78 
 
 8.49 
 1.20 
 
 5.72 
 1.76 
 
 7.36 
 .40 
 
 5.20 
 .40 
 
 2.27 
 1.56 
 
 1.72 
 4.52 
 
 1.11 
 
 .96 
 
 .48 
 
 .60 
 
 .70 
 
 Trace. 
 
 1.70 
 7.14 
 7.60 
 22.97 
 16.72 
 
 2.08 
 15.66 
 
 7.91 
 18.86 
 14.35 
 
 1.40 
 
 7.00 
 
 6.98 
 
 22.86 
 
 17.12 
 
 .25 
 36.42 
 
 2.60 
 16.79 
 
 2.65 
 
 .25 
 23.87 
 
 5.82 
 24.18 
 
 1.65 
 
 .20 
 14.36 
 
 7.75 
 32.26 
 
 1.10 
 
 3.57 
 
 1.66 
 
 2.70 
 
 6.12 
 
 8.86 
 
 6.70 
 
 2.72 
 13.33 
 
 2.70 
 13.61 
 
 3.85 
 8.86 
 
 20.99 
 6.31 
 
 16.36 
 9.36 
 
 16.81 
 11.13 
 
 18 months 
 
 old from 
 
 normal 
 
 soil. 
 
 Per cent. 
 
 Ash I 9.94 
 
 Ash. constituents: L 
 
 Silica (Si0 2 ) 9.37 
 
 Alumina (A1 2 3 ) . 2. 12 
 
 Ferric oxid 
 
 (Fe 2 3 ) 81 
 
 Manganese oxid 
 
 (M113O4) 2.41 
 
 Lime(CaO) 9.01 
 
 Magnesia (MgO). 5.70 
 
 Potash (K 2 0).... 21.09 
 
 Soda(Na 2 0) 19.48 
 
 Phosphorus pen- 
 toxid (P 2 5 )... 2.81 
 Sulphur trioxid 
 
 (S0 3 ) 2.62 
 
 Chlorin (CI) 13.37 
 
 Per cent. 
 6.60 
 
 2.84 
 6.02 
 
 Trace. 
 
 12.96 
 
 5.78 
 
 33.01 
 
 .60 
 
 8.36 
 
 22.93 
 8.01 
 
 These data show that there is a wide range of variation in the inor- 
 ganic constituents of the plant. Considerable differences have been 
 
 1 U. S. Dept. Agr., Dur. Chem. Bui. 107 (rev.), p. 238. 
 
 'Analyses of the roots were not made, for the reason that it is very difficult to remove 
 all traces of adhering soil from pineapple roots when grown in Hawaii. 
 [Bull. 28] 
 
14 
 
 observed in the percentages of the mineral elements in a given species 
 of plant when grown under different environments, such as are 
 afforded by different types of soil, climatic variations and lati- 
 tudinal changes, and the exact significance of the variations thus 
 induced isnot fully understood; but the variations in the compo- 
 sition of pineapple ash, herein reported, especially as regards the 
 lime, magnesia, and phosphorus pentoxid, are believed to have spe- 
 cial importance. The significance of these data has been fully inter- 
 preted in a previous publication which is devoted to a comprehensive 
 study of the function of manganese in plant growth. 1 
 
 At this time it is wished merely to call attention to the excessive 
 amounts of lime and the relatively smaller amounts of magnesia, as 
 well as a correspondingly smaller percentage of phosphorus pentoxid, 
 in the plants from manganiferous soils. As previously mentioned, 
 the occurrence of calcium oxalate crystals is much more abundant in 
 the chlorotic plants; in fact the presence of calcium oxalate forms 
 one of the noticeable characteristics in all parts of these plants ; and 
 while this so-called by-product occurs in considerable amounts in 
 normal pineapple plants, the amount is in great excess in the chlo- 
 rotic plants. Various authorities have discussed the occurrence of 
 calcium oxalate in plants, and in general they are agreed that one of 
 the functions of lime in plants is to neutralize the acids formed as 
 a result of metabolism. One of the principal acids thus formed is 
 oxalic, which has been supposed, by various authorities, to result from 
 at least two different sources: (1) It may arise from a decomposition 
 of carbohydrates during plant respiration; and (2) it is thought to 
 be derived, in some instances, from the breaking up of protoplasm. - 
 
 In chlorotic pineapples there have been observed a general disin- 
 tegration and breaking up of the organized structure of the proto- 
 plasm and the complete disappearance of the chloroplasts. With 
 this there is a simultaneous appearance of oxalate of calcium. From 
 these observations the conclusion may be drawn that the excessive 
 amount of oxalic acid in chlorotic pineapples results from a decom- 
 position of the protoplasm itself, and that its neutralization and sub- 
 sequent crystallization is made possible through the presence of 
 abnormal amounts of lime in the cell sap. 
 
 THE RIPENING OF THE PINEAPPLE FRUIT. 
 
 As has been clearly shown by numerous chemical analyses made at 
 this station, it is a peculiar feature of the ripening of the pineapple 
 fruit that no increase in the amount of sugar takes place during the 
 ripening process if the fruit has been removed from the plant. It 
 is apparent, therefore, that the materials which are transformed into 
 sugar are to be sought in other parts of the plant than the fruit. 
 
 i Hawaii Sta. Bui. 26. 
 [Bull. 28] 
 
15 
 
 Sections were made through all parts of the pineapple plant from the 
 base of the stem to the crown with the result that the distribution of 
 starch is found to be strictly in harmony with the chemical findings 
 of the ripening of the fruit. In the dead and partially decomposed 
 basal end of the stem there is relatively little starch, and that which 
 is present is for the most part removed some distance from the fibre- 
 vascular tissue. The parenchyma cells in the stem, with the except ion 
 of the dead base, are completely filled with starch ; in fact, these trunks 
 apparently contain as high a percentage of starch as potatoes or other 
 plant structures used in the commercial manufacture of starch. The 
 station has planned some experiments to show whether old pineapple 
 stumps which have heretofore been thrown away may be used com- 
 mercially for obtaining starch. The storage of starch continue- 
 upward to the attachment of the uppermost regular leaves, where it 
 suddenly ceases. As sections are made in the fruit stem above this 
 point, it is found that starch is almost entirely absent up to the point 
 where the small bracts are attached to the base of the fruit. Here, 
 especially in normal plants, the accumulation of starch is quite con- 
 spicuous. 
 
 In the very young fruit at flowering time small granules of starch 
 may be found at the base of the bra-cts under each eye and occasionally 
 throughout the substance of the fruit. At the base of the crown 
 leaves there is a considerable accumulation of starch and a few gran- 
 ules are found in the core. The crown in young fruits contains a 
 large quantity of starch. 
 
 It is a peculiar fact that old stumps connected only by means of 
 a dead stem with ratoon stems contain fully as much starch as the 
 latter. The old stumps are known to be capable of producing pine- 
 apple plants and have been especially recommended for highly man- 
 ganiferous soils. It is likely that in such cases the plants are able 
 to develop from the large supply of starch found in the stems. 
 Starch is quite abundant throughout the length of all normal leaves. 
 When the fruit is about half grown it contains only an occasional 
 starch grain here and there just underneath the green epidermis. 
 In ripe fruit it is almost impossible to find even a trace of starch 
 in any part of the fruit. It is evident from this distribution of 
 starch that the source of material to be modified by hydrolysis into 
 sugar is almost exclusively outside of the fruit. The few granules 
 of starch found under the green epidermis of unripe fruit and the 
 small quantity of starch in the crown are insufficient to make any 
 practical addition to the sugar content of pineapples which are 
 allowed to ripen after removal from the plant-. 
 
 In this connection it is interesting to note the fad that some pine- 
 apple grower- consider the crown as a parasite of the fruit or as 
 
 [Bull. 28] 
 
16 
 
 growing at the expense of the fruit. Experiments in removing the 
 crown from young fruits indicate that the core is thereby rendered 
 smaller and that the fruit is larger in cross diameter at the top, as- 
 suming a more cylindrical shape. The facts which have been stated 
 regarding the distribution of starch in the pineapple plant and 
 therefore of the possible sources of sugar in the ripening of pine- 
 apple fruits are in harmony with the findings of Hume and Miller, 1 
 that the sugar content is higher at the base of the fruit than in the 
 crown and higher nearer the core than at the surface. This would 
 indicate that the sugar enters the fruit through the fruit stem at the 
 base. 
 
 While pineapples in ripening after removal from the plant do not 
 develop any higher sugar content than they had at the time of re- 
 moval, they nevertheless undergo all the other processes which are 
 characteristic of ripening. The color changes are the same as those in 
 fruits which ripen on the plant and the fruit becomes soft and juicy. 
 It is a matter of common knowledge that only a small amount of 
 juice runs out of the cut surface of a green pineapple while much 
 larger quantities escape from similar cuts from ripe pineapples. This 
 is at least partly explained by reference to D and E of Plate II. In 
 D is seen a cell from the soft pulp of a completely ripened pineapple. 
 The cell wall is thin, delicate, and is easily torn. In fact the walls 
 here and there in ripe fruits are completely broken down in the 
 ripening process so that some of the larger cavities may be parts of 
 what was previously several cells. In the green fruits, on the other 
 hand, as shown in E, Plate II, the cell walls of the pulp tissue of the 
 fruit are much thicker. The thickening of these cell walls is com-" 
 posed of irregular masses of a collagenous nature. During the ripen- 
 ing process this material appears to be dissolved, leaving the thin cell 
 wall of the delicate tissue which is characteristic of the pulp of ripe 
 fruit. 
 
 THE CHEMISTRY OF RIPENING. 
 
 The physiology of the pineapple plant indicates some peculiarities 
 belonging to this plant, and which are different from those of most, 
 fruits. The chemical changes taking place during ripening have 
 previously received some attention at this station, 2 and in order to 
 have a more strict chemical basis for the interpretation of the physi- 
 ology already outlined, it is thought that a further discussion of these 
 data will be of interest. It has been shown that the average composi- 
 tion of the green fruit, just before the beginning of the ripening 
 process, is as follows : Acidity, as sulphuric acid, 0.39 per cent ; fiber, 
 
 1 Florida Sta. Bui. 70. 
 
 2 IIaw;iii Sta. Rpt. 1910, pp. 45-50; Jour. Indus, and Engin. Chem., 3 (1911), pp. 
 403-40.1. 
 
 [Bull. 28] 
 
 
17 
 
 0.17 per cent; solids in the juice, G.89 per cent; total hydrolyzable 
 carbohydrates, expressed as invert sugar, 5.80 per cent ; reducing 
 sugars, as invert sugar, 3.29 per cent; sucrose, 1.72 per cent; and 
 total sugars, 5.01 per cent. 
 
 The point of special interest in these data is the small percentage 
 of sugars in the green fruit. It should be borne in mind in this con- 
 nection that the above data were secured from fully grown fruit 
 which, so far as could be judged, were just at the beginning of the 
 ripening process. In addition, these analyses were made by the use 
 of the fruit itself, rather than the juice. While the reducing sugars 
 and sucrose make up a small percentage of total sugars the hydro- 
 lyzable carbohydrates, which were determined by boiling samples 
 of the fruit with hydrochloric acid, show that the storage of reserve 
 material in the growing pineapple is slight, and if severed from the 
 plant at this stage it can not possibly develop a normal sugar con- 
 tent in subsequent ripening. Pineapples gathered green and allowed 
 to ripen afterwards were found to have the following average com- 
 position: Acidity, 0.58 per cent; fiber, 0.22 per cent; solids in the 
 juice, 6.45 per cent; reducing sugars, 1.22 per cent; sucrose, 3.90 
 per cent; total sugars, 4.12 per cent; and total hydrolyzable carbo- 
 hydrates, as invert sugar, 4.35 per cent. 
 
 The principal changes that take place in this process are the con- 
 version of reducing sugars into sucrose, and a slight increase in 
 acidity. There is a pronounced development of flavor and a general 
 softening of the tissues, but the true fiber is not materially changed. 
 The average composition, when approximately one-fourth ripe, was 
 found to be as follows: Acidity, 0.65 per cent; solids in the juice, 
 8.68 per cent; reducing sugars, 2.74 per cent; sucrose, 4.42 per cent; 
 total sugars, 7.16 per cent; and when half ripe the fruit contains: 
 Acidity, 0.65 per cent; reducing sugars, 2.97 per cent; sucrose, 6.74 
 per cent ; and total sugars, 9.71 per cent. When allowed to ripen nor- 
 mally on the plant, the composition was found to be as follows: 
 Acidity, 0.74 per cent; reducing sugars, 4.23 per cent; sucrose, 7.88 
 per cent ; and total sugars, 12.11 per cent 
 
 The composition at the several stages of ripening shows that there 
 is a rapid accumulation of sugars, especially sucrose, and a slight in- 
 crease in acidity during the development of the fruit. From a study 
 of the physiology of this plant we can better understand the analytical 
 data. It has been shown that the normal pineapple plant stores up 
 large amounts of starch in the stalk and base of the leaves, whereas 
 only faint traces of starch could be detected in any portion of the 
 fruit at any stage of its development. The fruit stem was found to 
 contain small quantities of starch ; also there are scattering granules 
 in the cells immediately adjacent to the epidermis. These cells were 
 
 [Bull. 28] 
 
18 
 
 also found to contain a small amount of starch adhering to the chloro- 
 plastids. The deeper- lying tissues rarely contain any starch ; neither 
 was dextrin detected in more than mere traces; and from the results 
 of acid hydrolysis we may conclude that the green fruit contains no 
 substance of importance that is capable of giving rise to sugars during 
 subsequent ripening. 
 
 The chief carbohydrates produced in the plant, then, may be con- 
 sidered to be of the nature of sugars and starch, and these may be" 
 looked upon as being produced somewhat as follows : The protoplasm 
 transforms carbon dioxid and water into sugars by the intervention 
 of chlorophyll, just as is done in all plants. The excessive accumula- 
 tion of sugar in the chlorophyll-bearing cells is prevented by its 
 transformation into starch, which, in turn, is stored principally in 
 the stalk. During the vegetative growth of the fruit relatively small 
 amounts of carbohydrates are transferred to it, but in the normal 
 ripening process there is an enormous accumulation of sugars in the 
 fruit, which sugars are derived from the carbohydrates previously 
 stored as starch in the stem. 
 
 Normally, pineapples stand almost perpendicular and are some- 
 what protected from the direct rays of the sun by the crown. Occa- 
 sionally there are to be observed in the fields pineapples that have 
 weak steins, which results in the fruit becoming turned over and 
 exposing one side to the direct rays of the sun. The pineapples 
 that are thus exposed become blanched on the upper side, which ap- 
 pears to mature earlier than the lower and more protected surface. 
 Such pineapples also are less palatable in the upper and exposed 
 portion. 
 
 With a view of determining the composition of such fruits a num- 
 ber of analyses have been made. These pineapples were sampled in 
 such way as to secure one portion from the upper side and one from 
 the lower side. Partial analyses of these portions are recorded as 
 follows : 
 
 The composition of upper and lower portions of pineapples. 
 
 Serial 
 No. 
 
 
 Acidity 
 asH 2 S0 4 . 
 
 Reducing 
 
 sugars 
 
 calculated 
 
 as invert 
 
 sugar. 
 
 Sucrose. 
 
 Total 
 sugars. 
 
 Polarization. 
 
 Direct. 
 
 Invert. 
 
 Tempera- 
 ture. 
 
 119 
 
 
 Per cent. 
 0.51 
 .51 
 .40 
 .74 
 .88 
 .98 
 .72 
 .55 
 .63 
 .69 
 
 Per cent. 
 3.06 
 4.35 
 4.00 
 3.44 
 3.33 
 2.98 
 4.17 
 4.54 
 3.64 
 3.83 
 
 Per cent. 
 5.58 
 8.42 
 4.81 
 6.17 
 6.78 
 8.41 
 7.48 
 8.45 
 6.16 
 7.86 
 
 Per cent. 
 
 8.64 
 12.77 
 
 8.81 
 
 9.61 
 10.11 
 11.39 
 11.65 
 12.99 
 
 9.80 
 11.69 
 
 4.1 
 6.4 
 3.4 
 4.7 
 4.9 
 6.4 
 5.6 
 6.3 
 
 °V. 
 
 -3.0 
 -4.3 
 -2.8 
 -3.1 
 -3.7 
 -4.3 
 -4.0 
 -4.5 
 
 °C. 
 31.0 
 
 119 
 
 
 31.4 
 
 120 
 
 
 31.7 
 
 120 
 
 
 32.5 
 
 121 
 
 
 31.7 
 
 121 
 
 
 30.8 
 
 122 
 
 
 28.6 
 
 122 
 
 Lcwer side 
 
 29.7 
 
 
 Average, upper side. . . 
 Average, lower side . . . 
 
 
 
 
 
 
 
 
 
 
 [Bull. 28] 
 
19 
 
 These data show that a considerably greater amount of sucrose w 
 deposited in the lower and more protected portion of the fruit. This 
 may be partially accounted for by the fact that the ripening process 
 is abnormal in character and more hastened in the blanched portion 
 of the fruit. There seems to be no evidence for believing that the 
 hydrolysis of starch in the stalk and the diffusing of sugars to the 
 fruit continues after the fruit becomes thoroughly ripe, even if it 
 be left attached to the plant. The period of transference of sugars 
 to the blanched portion of such pineapples, therefore, is shorter and 
 consequently it should contain less sugars. In addition, osmosis may 
 in some way be modified by the effects of direct rays of the sun on 
 the fruit. 
 
 SUMMARY. 
 
 The root system of pineapples is very variable and particularly 
 sensitive to adverse soil conditions. When grown in manganiferous 
 soil the roots are less extensive and the ends of the roots are charac- 
 terized by the development of swollen tips, the appearance of which 
 seems to mark the cessation of the lateral growth of the roots, death 
 and decay immediately following their development. The cells im- 
 mediately beneath the epidermis of the roots are also somewhat more 
 brown than are normal roots. 
 
 The stem of pineapples serves as a repository for starch and con- 
 tains large amounts of this substance. 
 
 The leaves of pineapples in common with other members of Brome- 
 liaceaa contain several rows of palisade cells which contain nothing 
 but cell sap, and the chlorophyll is confined to the spongy paren- 
 chyma in the lower three-fifths of the leaf. The fruit contains only 
 faint traces of starch during early growth and when it reaches 
 maturity starch is absent from it. 
 
 The most conspicuous effect of manganese on this plant is seen in 
 the bleaching of the chlorophyll which first begins to fade, the 
 chloroplasts lose their organized structure, and later the color dis- 
 appears altogether. Oxalate of calcium is much more abundant in 
 pineapple plants growing on manganiferous soils. The ash of such 
 plants also contains considerably more lime and less phosphorus 
 pentoxid and magnesia than when grown on normal soils. 
 
 During the growth of the fruit relatively small amounts of sugars 
 are stored in it, but within the short period of normal ripening there 
 is a rapid accumulation of sugars in the fruit. Pineapples gathered 
 green do not develop a normal sugar content in subsequent ripening. 
 The sugars of the fruit are derived from the starch previously stored 
 in the stalk. 
 
 [Bull. 28] 
 
20 
 
 The study of the pineapple shows that it is exceedingly sensitive to 
 adverse physical and chemical conditions in the soil. So far as is 
 known at present, there is no really satisfactory program by which 
 pineapples can be grown on highly manganiferous soils. It seems 
 best to use such areas for other crops less sensitive to manganese. 
 The best method of handling pineapples on manganiferous soils con- 
 sists in applying soluble phosphates and planting old stumps instead 
 of suckers. 
 
 [Bull. 28] 
 
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