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" pears BUREAU OF ‘CHEMISTRY BULLETIN No. 142. cit oa ab W. WILEY. chief of Bureau, { { Sot ) Bae st. 5 . Fruits. a Bi bcs. Carbon Dioxid by Peaches. Bt > —. * tion of Fruit Under Adiabatic € Conditions. Lag oh ot @, GORE, ASSISTANT CHEMIST, DIVISION OF FOODS. | as = X Gs Mea aie ; tk 7 bal bee At i 5 WASHINGTON; | GovpRNaENT. - PRINTING OFFICE. . e 1911. oe DEPARTMENT OF AGRICULTURE, I. The Effect of Teri peratare on ‘the Respiration of 3 8 ee II. The Effect of Picking on the Rate of Evolution of HII. The Rate of Accumulation of Heat in the Respira- PUDIES ON Le RESPIRATION, ORGANIZATION OF BUREAU OF CHEMISTRY. = H. W. Witezy, Chemist and Chief of Bureau. F. L. Dunuap, Associate Chemist; Acting Chief in absence of Chief W. D. Bicetow, Assistant Chief of Bureau. F. B, Linton, Chief Clerk. A. L. Pierce, Editor. A. E. Draper, Librarian. Division of Foods, W. D. Bicetow, Chief. Food Inspection Laboratory, L. M. Totman, Chief. Food Technology Ee boratary. E. M. Cuace, Chicf, and Assistant Chief of Division. Oil, Fat, and Wax Laboratory, H. 8. Barus, Chicf. Diviion of Drugs, L. F. Kesier, Chief. Drug Inspection Laboratory, G. W. Hoover, Chief. Synthetic Products Laboratory, W. O. Emery, Chicf. Essential Oils Laboratory, wnder Chief of Division. Pharmacological Laboratory, WM. SaLant,. Chief. Chief Food and Drug Inspector, W. G. CAMPBELL. Miscellaneous Division, J. K. Haywoop, Chief. Water Laboratory, W. W. SKINNER, Chief. ° Cattle-Food and Grain Laboratory, G. L. BipweEtt, Acting. Insecticide and Fungicide Laboratory, C. C. McDoNNELL, Chief. Trade Wastes Laboratory, under Chief of Division. Contracts Laboratory, P. H. WALKER, Chief. Dairy Laboratory, G. E. Parricn, Chief. Food Research Laboratory, M. E. Pennineton, Chief. Leather and Paper Laboratory, F. P. Vrerrcn, Chief. Microchemical Laboratory, Bb. J. Howarp, Chief. Physical-Chemistry Laboratory, C.S. Hupson, Chief. Sugar Laboratory, A. H. Bryan, Chief. Sections: Animal Physiological Chemistry, F. C. WEBER, in Charge. Bacteriological Chemistry, G. W. Sties, in Charge. | Enological Chemistry, W. B. Atwoopn, in Charge. ; 3 Nitrogen, T. C. Trescor, in Charge. Plant Physiological Chemistry, J. A. LeCierc, Chief. - Food and Drug Inspection Laboratories: Boston, B. H. Smiru, Chief. Buffalo, W. L. Dusots, Chief. Chicago, A. L. Winton, Chief. Cincinnati, B. R. Harr, Chief. ; 2 ae Denver, R.S. Hitrner, Chief. eo ot Wee ee ig he a ib: Detroit, H. L. Seuxvuz, Chief. x Galveston, T. F. Parr, Chief. + : Honolulu, Hawaii, E. B. BLANCHARD, ‘Acting z : Kansas City, Mo., EW LIEPSNER, Chief. ‘ Nashville, R. W. Batcom, Chief. 4 New Orleans, W. J. McGrz, Chief. 5, a New York, R. E. Doourrrie, Chi:/. : aeees Sa Omaha, 8S. H. Ross, Chief. — Z : Philadelphia, C. S. Bruston, Chief. Sd here 1 .. Pittsburg, M. C. ALBREcH, Chic. ss Portland, Oreg., A. L. KN isELy, Chief. ere Ag Hehe ees aa St. ews, D. B, BisBeE; Chicf. - . SOT : See St. Paul, ‘< 6 Mebavie Chief. oi G Ss one ee San Francisco, R. A. Goutp, Chief. rt sche ee Savannah, W. C. Burnet, Chief. Se ee ee eS Ee Seattle, H. M. Loomis, Chief. Egt ea : Ste eee Issued August 4, 1911. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF CHEMISTRY—BULLETIN No. 142. H. W. WILEY. Chief of Bureau. STUDIES ON FRUIT RESPIRATION. I. The Effect of Temperature on the Respiration of Fruits. Il. The Effect of Picking on the Rate of Evolution of Carbon Dioxid by Peaches. Wi. The Rate of Accumulation of Heat in the Respira- tion of Fruit Under Adiabatic Conditions. BY H. C. GORE, ASSISTANT CHEMIST, DIVISION OF FOODS. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1911. LETTER OP PRAN Sita shAt: U.S. DEPARTMENT OF AGRICULTURE, BUREAU OF CHEMISTRY, Washington, D. C., April 28, 1911. Str: I have the honor to submit for your approval three studies on fruit respiration made by H. C. Gore of this bureau in cooperation with the Bureau of Plant Industry. Mr. William A. Taylor, acting chief of that bureau, has been in close touch with the work, making suggestions from time to time which have increased its scope and use- fulness. I recommend that this manuscript be published as Bulletin No. 142 of the Bureau of Chemistry. Respectfully, HW... Winey, Chief of Bureau. Hon. JAMES WILSON, Secretary of Agriculture. 2 CONTENTS. I. Effect of temperature on the respiration of fruits....................---- ri Gr@ Cie om ey sees Beech a Pe cle eats > ky perl aad py Mare ahaha ene Selection,and preparation of the aruit.- 3 - oo. sced oti sie dee Peete s 2 Deseripiion of apparatus andiamethods. 2 4): -.csseuiee {ses oes as 442. Absorphion apparatus seme semua o. boos. cep kona epee are ape QRS Mewmperaturesh swap peMser Wie ehh tn du vee a utes Uae ele 2 Regulation of imenbator, Wiesel alae. eeu lek dea Mioe «4 Collection and estimation of carbon dioxid-......-....-...-...--. Statement ohresul tsi3s ao sh oe Seen ia icy bei Mpa re, Mase weston, Giires lisesi ier ek ae oh Eh ey see eles aio duet hh Rig NE II. Effect of picking on the rate of evolution of carbon dioxid by peaches. .. . A pparatisandanethodvemployede yt: sat eos ui iessatlae baa lk Resuiltsvobtarmecd sites oy be eke yee ar tah alka A Spee REAL) Ou 5) III. Rate of accumulation of heat in the respiration of fruit under adiabatic COMGIGIOMS yas enke tee sue Naik LOS el Myla ace Mid AL ab pecs (lasises.ebseli- hea amos tacit Ay) ade es Eh ey ye adler Baye gual ei ko Formula for calculating rate of heat accumulation..................-- Application of formula to'specilic cases... ace aepigse 4a eo! SSE AVOTE Ff Aaa Ae le Me ages Panay ATS er eae Pay tC EuS ir a eran SU Ce ae oe Fie. 1. . Electrically-heated, constant-temperature incubator........-....----.- “'Detarl of thermostats vue ooo) Ne cee ev A SAG eee gee . Effect of temperature on the rate of respiration of blackberries, cur- 10. 1. 12. 13. 14, 15. 16. ie . Effect of temperature on the rate of respiration “of grapes . Effect of temperature on the rate of respiration of lemons, oranges, ILLUSTRATIONS. Purthying and sabsorption-apparatusscn = seco see. ee ese ee ee eae rants, huckleberries, raspberries, and strawberries . Effect of temperature on the rate of respiration of peaches and apples. . . Effect of temperature on the rate of respiration of peaches, pears, and persimmons, mangos, and pineapples....................- . Data on the respiration of Delaware grapes, showing the evel edt car- bon dioxid plotted directly and logarithmically................... Effect of temperature on the rate of respiration of blackberries, cur- rants, huckleberries, raspberries, and strawberries, plotting the carbon dioxid logarithmically.) cee bce ae ee eee Effect of temperature on the rate of respiration of peaches and apples, plotting the:earbon’ dioxid logarithmically 3:20 5.5.2 Effect of temperature on the rate of respiration of peaches, pears, and plums, plotting the carbon dioxid logarithmically...........-.-..- Effect of temperature on the rate of respiration of grapes, plotting the carbon: dioxid logarithmiacalliy..) 25555240 Woe ie aye eee Effect of temperature on the rate of respiration of lemons, oranges, persimmons, mangos, and pineapples, plotting the carbon dioxid logartthmarcallby:: ieee ee Ae OST ESSE Ek Spt Sen cea eee Distribution, about the mean, of the experimentally found values of a (rate at which the logarithm of the respiratory activity changes per degree of rise in temperature)... Agiey Beage kes Saar Theoretical rate of increase in the fopeoree) ol ernie held Pdee adiabatic COmdItIONS iis 2. os eee ee te else cians teh ase oer nee Theoretical rate of increase in the respiration and temperature of fruit held under adiabatic conditions..........-e-eeeeee sib Sebiowe eee cee 24 28 37 38 STUDIES ON FRUIT RESPIRATION. I. EFFECT OF TEMPERATURE ON THE RESPIRATION OF FRUITS. INTRODUCTION. The literature on the effect of temperature on the respiration of plants is well covered up to the year 1905 by the review of Czapek,} who notes that de Saussure and his predecessors were well acquainted with the fact that a rise in temperature increases both the rate of absorption of oxygen and the rate of evolution of carbon dioxid. Van’t Hoff? early noticed that the respiration of plants followed the empirical rule that the rate increases two or three times for each rise of 10° C.2 Important studies were published in 1905 by Miss Mat- thaei‘ on the effect of temperature on the respiration and assimila- tion of leaves, and Kuyper® has recently published results on the effect of temperature on the respiration of seedlings. But little work has been reported in the literature on the respiration of fruits. The investigations of Gerber® showed that the rate greatly increased on warming. Bigelow and Gore’ found that the formation of carbon dioxid by apples was much more rapid at cellar temperatures than in storage at 0° C., and F. W. Morse® confirmed these results and showed ‘‘that at summer temperatures apples will undergo respir- atory metabolism from four to six times as rapidly as in modern cold storage.” The work herein reported was undertaken to obtain more infor- mation along this line, which is of special value at this time, when such rapid advances are being made in the field work on the trans- portation and storage of fruit. The plan followed consisted, in brief, in determining the rate of evolution of carbon dioxid from fruit kept in the dark at different temperatures and supplied freely with air. 1 Biochemie der Pflanzen, 1905, 2 : 397. 2 Htudes de dynamique chemique, 1883. 8 This point is further discussed on p. 28. 4 See p. 28. 5Kon. Akad.. van Weten Amsterdam, 1909, 12 (1): 219; and Recueil des Travaux Botan. Néer- landais, 1910, 7: 131. 6 Ann, des sciences naturelles, 1896, (8), 4: 1. 7U.S. Dept. Agr., Bureau of Chemistry, Bul. 94. 8 J. Amer. Chem. Soc., 1908, 80 : 876. 6 STUDIES ON FRUIT RESPIRATION. SELECTION AND PREPARATION OF THE FRUIT. Whenever practicable the variety and locality were selected by Wm. A. Taylor, of the Bureau of Plant Industry, in order that the study should have as direct an application as possible to field work. The fruits so selected came from localities in which the particular variety was grown under typical conditions on a commercial scale. The fruit from the Arlington farm was usually picked from the trees on the day preceding the date of the beginning of the experiments. Except where noted, none of the fruit had been subjected to cold storage or any known condition which could cause abnormality. Each sample was prepared for the experiment by first eliminating unsound or injured specimens. The sample was then divided into two or more weighed lots for the measurement of the rate of respira- tion at different temperatures. After weighing, each lot of fruit was kept at the temperature at which it was desired to measure the rate of respiration for several hours or overnight before starting the exper- iment, in order that it might acquire the temperature of its surround- ings. To effect this the fruit was placed either in open baskets beside the desiccators in which it was to be run later, or in the desiceators themselves. In the latter case a rapid current of air was passed through them in such a way that the air surrounding the fruit was continuously renewed. In the case of the small fruits, the greatest care was exercised in selecting and handling them during the opera- tions of weighing and placing in desiccators. The best specimens as far as freedom from any suspicion of spoilage was concerned were selected for the experiment at room temperature, as it was realized that here was the greatest danger of vitiation of the results, owing to the activities of yeasts and other microorganisms. The red rasp- berries, in particular, were extremely delicate, and it was difficult to avoid breaking them during the necessary handling of the fruits. Similar precautions were necessary in the case of blackberries. With the red and black currants, only berries attached to stems were used, to lessen the chances of deterioration due to the development of microorganisms at the pedicels. At times, in the work on the small fruits, the experiments were run for several days in order to obtain duplicate determinations on the same lot of fruit. In all cases well agreeing duplicates were obtained except where visible deterioration due to spoilage occurred. The first lot of black raspberries had per- ceptibly molded at the close of the period of measurement in the desiccator kept at room temperature, and accordingly, a few days later, a second sample of fruit from the same patch was run. This sample also molded very slightly. It is probable that, in both eases, increases of carbon dioxid due to activities of microorganisms were very small. The huckleberries and the wild blackberries were obtained EFFECT OF TEMPERATURE. 7 from the local market, and no reliable data as to place of origin could be obtained. The huckleberries were identified by F. V. Coville, of the Bureau of Plant Industry. The peaches from Georgia had been shipped in refrigerator cars and were cold when received. The data for the Carman variety were obtained first on a sample of hard-green fruit. Weighed lots of the same sample of peaches were allowed to ripen at room tem- perature and were then examined to determine whether there were differences in the rate of respiration between the green and the ripened fruit. The locally grown peaches, Champion, Cunnett, and Elberta, were picked when hard-ripe and well colored. The lemons were divided into two lots, the fruit which was still partly green and that which was fully yellowed, and examined separately. Both the oranges and lemons were freshly picked fruit sent by express from California. The pineapples and Japanese persimmons were well colored but firm; the latter did not soften while under observation. The mangos were highly colored and eating-ripe. The apples were all recently picked, the two summer varieties, Jefferis and Summer Pearmain, having been gathered on the day previous. The three lots of winter apples from California were well colored, freshly picked fruit sent by express. The four varieties of Vinifera grapes were purchased on the local market, those from California probably having been shipped in refrigerator cars. Two attempts were made to determine the effect of temperature on the rate of evolution of carbon dioxid from bananas but without success on account of the very rapid acceleration in the rate of evolution of carbon dioxid with ripening. These trials showed that the rate of physiological activity increased greatly even overnight. The effect of temperature on the respiration of bananas will be the subject of further study. DESCRIPTION OF APPARATUS AND METHODS. ABSORPTION APPARATUS. The apparatus used in the measurement of respiration intensity at each temperature-is shown in fig. 1. The air entering the desic- cator was first drawn through a long tube filled with soda lime to free it from carbon dioxid; it was next passed through a wash bottle containing baryta water and then through a drying tower containing calctum chlorid. The wash bottle was useful in testing the apparatus for tightness and for insuring that the air was properly purified, while the drying tower was used in the measurements at room, ice-box, and cold-storage temperatures, as it was feared that the 8 STUDIES ON FRUIT RESPIRATION. use of air nearly or quite saturated with water vapor would cause excessive humidity. The air entered each desiccator near the top and was removed through a delivery tube reaching nearly to the bottom. From the desiccator it was drawn through a Reiset absorp- tion apparatus, then through another wash bottle containing baryta water and to the suction pump. The air current was drawn through at the rate of from 2 to 4 liters per hour. The desiccators were kept in the dark usually at some distance from their respective sets of purifying and absorption apparatus. The gases were led to and from them in copper tubes (one-fourth Ain. | (18 c] “O~ REISET ABSORPTION TUGE = Fh l i 2 i Pai pe at > laa oa 2 BTS e f Sr a l Gare re Sh ‘= rs | fa . | lke i lee Fic. 1.—Purifying and absorption apparatus. inch outside diameter and one thirty-second inch wall) which pos- sessed, in addition to the advantage of being infrangible, the property of being easily bent into the required shapes. Im all apparatus care was taken to have the ends of the glass or copper tubes come together closely at the joints, and to avoid entirely leading gases in rubber tubes because of the well-known fact that rubber absorbs carbon dioxid selectively... The desiccators were of the tubulated Scheibler pattern, 8 or 10 inches in diameter. No difficulty was experienced in fitting the covers tightly, provided the glass surfaces were plane and finely ground. The two-holed stoppers carrying the tubes were well lubricated with vaseline, forced tightly into place, and tied. 1 Morse, H. N., Exercises in Quantitative Chemistry, 1905, p. 77. EFFECT OF TEMPERATURE. 9 TEMPERATURES. The fruits were usually held at three different temperatures, although at times four were employed and in several cases only two are recorded. The four temperatures were as follows: (1) A cold- storage temperature of about 2° C., which was usually very steady and rarely varied more than 1° durmg arun. (2) An ice-box tem- perature of from 7.1° to 12.7°C. Thetemperature in this case usually rose slowly during a determination as the surface of the ice decreased with melting, and rarely varied more than 2°C. during a determina- tion. (3) Room temperature, which varied according to the season of the year from 20.5° to 31.2° C., but was very steady from day _ to day, as the darkened cabinet in which the desiccator was kept ee ee j 7 Y | Bi WCW Y F A | i | [ { : so _ SaaS SS STNG | tae aN UY, =) Za Se eran Te ae Y Fic. 2.—Electrically-heated, constant-temperature incubator. , was situated out of the way of drafts. (4) The incubator tempera- ture, from 32.6° to 35.6°C., was automatically regulated and varied at most but 0.2° C. during a determination. The temperatures were taken at the beginning and at the end of a run by reading short corrected thermometers placed in the desiccators among the fruit. REGULATION OF INCUBATOR. The incubator in which the fruit was kept when it was desired to measure the respiration at a higher temperature than that of the room consisted of a wooden cabinet with well-fitting doors. The arrangement of the heating device is shown diagrammatically in fig. 2. The incubator was large enough to contain the desiccator, A, an electric fan, C, an electri¢ heating coil, B, a thermostat, D, and various lots of fruit. In planning the method of heating slightly 95678°—Bull. 142—11——2 10 STUDIES ON FRUIT RESPIRATION. above the highest room temperature attained during the summer, it was necessary to keep in mind the fact that such an incubator has a small heat capacity and the heater must likewise be of low heat capacity, so that the temperature may cease to rise as soon as the circuit is opened; otherwise the temperature may rise and fall through a wide range. The heating device, B, was a set of coils taken from an electric toaster. This was placed directly in front of the fan, C, so that the heat as suppled was quickly distributed through the chamber. The thermostat, D, consisted of a long coiled glass tube filled with mercury. It was closed at one end, mounted on a wooden frame not shown, and provided at the other with a simple device for making and breaking a low-tension electric current as the temperature varied. The essential part of the thermostat is shown in detail in fig. 3. While involving nothing new in principle, the arrange- ment has been found to combine sensitiveness with stability. Electric connection is made with the mercury of the thermostat through the plat- inum wire A. It is necessary that mercury of high purity be used, that its surface be kept free from dust, and that sparking at the point of contact between the mercury and the plati- num wire be reduced toa minimum. The heat was supplied by the 110-volt, direct lighting cur- rent which was cut in and out by a telegraph relay, E, actuated by opening or closing the small current at the point of contact in the thermostat. Two points in the electrical arrangements deserve special mention. First, sparking was Fig. 3.—Detail of ther- avoided in the usual manner by placing con- ae densers G and H across the spark gaps at F and I, respectively. In making and breaking the heating current it was found that if the condenser was too large enough energy was stored in it to cause small sparks when the circuit was closed at the con- tact points, causing them to adhere at times so that they failed to separate at the pull of the electro-magnet. The condenser finally used for breaking this current consisted of three pairs of plates of tin foil separated by waxed paper. The effective area of each sheet was about 500 square centimeters. The second point is the method of getting the small constant current which is made and broken in the thermostat. This was obtained as a shunt from the 110-volt direct current by using a resistance coil, J, rated at 1,000 ohms, con- SST may eT TTTTITTTTITITTT tiie! y EFFECT OF TEMPERATURE. 11 sisting of a coil of wire wound on a porcelain tube over which enamel had been baked, with 8 taps taken off at even points along the tube. The small shunted current used in actuating the relay was taken from two adjacent taps. It was thus at a potential difference of about 11 volts when the resistance coil was connected in the 110-volt circuit. A rheostat, K, was found useful in regulating the amount of_ current supplied to the heater. If the amount sent through is but slightly more than sufficient to supply the usual losses of heat from the incubator, the current will be on nearly all of the time and the regulation of the temperature will be very exact. If the room temperature should be considerably lowered, however, sufficient heat would not be supplied. If, on the other hand, much current is used, the heat would be on for but a small fraction of the time, but the temperature would vary within wider limits. It was found well to adjust the rheostat so that the circuit was closed about half the time. The current strength was about 3 amperes. Except for the thermostat, which should be made by an expert glass worker, the entire outfit may be selected from electrical sup- plies now on the market. COLLECTION AND ESTIMATION OF CARBON DIOXID. As stated on page 8, the air was withdrawn from each desiccator and passed through a Reiset absorption apparatus where the carbon dioxid was quantitatively removed. The Reiset tubes were similar to those used by Reiset 1 and by Brown and Escombe.? Each apparatus consisted of a long, wide glass tube fixed vertically in a side-arm flask by a gasket made from a rubber stopper. The tube was 50 cm high and 2 cm in diameter. Platinum disks were fixed at the lower end, 12.5 and 25 cm, respectively, from the bottom. These disks were pierced with fine holes about 0.5 mm in diameter and their edges sealed into the walls of the tube. When in operation, the absorbing liquid rises in the tube, the air which is then drawn through the lowest disk “rises through the column of liquid in a rapid stream of small bubbles which are broken up and reformed at each of the two succeeding plates, thus producing a very effective ‘scrubbing’ action.” ° Generally 100 cc of normal sodium hydroxid were used as the absorbent, but at times double normal alkali was employed. During the early part of the work two Reiset tubes connected in series were used, but later it was found that one was sufficient unless very large amounts of carbon dioxid were to be collected. 1 Compt. rend., 1879, 88: 1007; 1880, 90: 1144; Hempel, Gas Analysis, 1902, p. 110. 2 Royal Society, London, Proc. 1905 (B) 76: 29. 3 Brown and Escombe, loc. cit., p. 33. 1h STUDIES ON FRUIT RESPIRATION. The method of double titration employed by F. W. Morse! and by Brown and Escombe ? was used, in which phenolphthalein and methyl orange are employed successively. It was found convenient to rinse the soda solution into a precipitating jar of about 650 cc capacity. If much carbon dioxid had collected the volume of the solution to be titrated was increased considerably by adding water, and it was found necessary to stir rapidly, and to have the tip of the burette well down in the solution; these precautions tend to avoid loss of carbon dioxid due to the presence of local excess of acid. Normal hydrochloric acid was added until the solution was colorless. Methyl orange was then added and the titration finished. The sodium hydroxid solution used contained a small known amount of carbonate whose value expressed in terms of normal hydrochloric acid was subtracted from the results of each titration. Kiister? has critically reviewed the volumetric methods for the determina- tion of carbon dioxid. He found that this method of double titra- tion was faulty on account of the fact that sodium bicarbonate is faintly alkaline to phenolphthalein, and low results for carbon dioxid may consequently be obtained. If the titration with hydrochloric acid is carried to the point where the solution is colorless to reflected light while still containing a trace of red color when compared with a control, Kuster found that accurate results were obtained, but notes that the end point is empirical. He states also that methyl orange is strongly colored by carbon dioxid and the titration with this indicator should be carried to a normal tint, which is defined as that of an aqueous solution of the indicator, of the same concen- tration as the one used in the titration, saturated with carbon dioxid. The writer was not familiar with the work of Kiister until the study was well under way, and it was then considered best not to change the method. No control was used in judging when the phenol- phthalein pink disappeared, and the end point was thus essentially the empirical one described by Kiister. The error caused by the uncertainty of the end point can hardly amount to more than 1 per cent of the amounts of carbon dioxid found. Very accurate results were obtained by Kiister by using the Winkler > method in which solution of barium chlorid is added in excess. ‘The titration is then made without filtering, using phenolphthalein. This there- fore appears to be the best volumetric method of determining carbon dioxid. 1 Loc. cit. ; 2 Loe. cit.; Royal Society, London, Philos. Trans. 1900, (B) 198: 289. 3 Certain minor refinements used by Brown and Escombe in their work on leaves, in which very small amounts of carbon dioxid were estimated (using sodium hydroxid prepared from sodium, using dilute acid in titrating, and taking measures against contamination from the atmosphere of the solutions to be titrated during their transfer from the absorption apparatus), were omitted, as blank determinations were found to give constant results irrespective of slight changes in technique. 4 Zts. anorg. Chem., 1896, 13: 127. 5 Cl. Winkler, Massanalyse; see also B6ckmann, Untersuchungsmethoden, pp. 408, 411, and 413; through Kuster, loc. cit. sf x) wg Pi é >| 0 p moments © pote “ i i 4 ale Ce RAE rome Or We eN Bee ener, CONV mee Mite vay a Mts nd i soe A ee Ome boa ee eee aad a Site oo ee ay eS q a Pt aie hata Ge wie eee ea CCC es Se ?29 30 3/32 EFFECT OF TEMPERATURE. | bes STATEMENT OF RESULTS. The kind and variety of fruit, the locality where grown, date, weight of fruit used, the interval during which the carbon dioxid was collected, the average temperature during this period, and the carbon dioxid formed expressed in milligrams per kilogram of fruit per hour, are given in Table 1, following. The data have been calculated also in terms of the volume of carbon dioxid per kilogram per hour. The time in hours which will be required for the fruit to give off its own volume of carbon dioxid has been calculated on the assumption that 1 kilo- gram of fruit occupies 1,000 cc. The results in terms of milligrams of carbon dioxid per kilogram per hour are given graphically in figs. 4 to 8, inclusive. In plotting, curved lines have been used in con- necting the several determined points. While straight lines are more commonly used, particularly when but few points are deter- mined, it is believed that the curves show better the constantly accel- erated activity as the temperature rises. They were drawn with a spline and spline weights. TaBLE 1.—Lffect of temperature on the rate of respiration of fruits. mor KOON anO NRN HP RR DOWD 33 Carbon | © = = GS dioxid. =O = Ea» SoG e ob A 5 5 =| ns, tou on 15 q 5, Sg : 5 =| d Locality where Date a5 5 E oe 5 ie é : aia ; = mo |e S) rs) Kind and variety of fruit. grown. manera 3s a 5 5 ‘AS s\s a2 3 = = bb 5 at cS a= a4 % Se ni x a SF o = a |f38| 8 [8s Heel oss Of HO a ro) eH 5 g 3 vo o |2sa\ 5 BAS) SH &|HSS eaitaa < > = Strawberries: : 1910. Grams.|Hours.| °C Hours. Martin’s New Queen....-- Arlington, Va...-- June 10; 1,000] 18.3 | 23.9} 130] 72.0 13.9 ; 18.3 | 10.1 41} 21.6 46.3 Gam Given. tases ree eee Washington, D.C.| June 17 | 1,000] 18.0] 26.2] 151] 84.3 11.8 18.0 | 10.6 46 24.3 41.2 20.0 | 2.0 117 8.7 | 114.9 Black raspberries: CAN SHSeecice ee eats sare Me West Falls] June 18] 1,000] 20.0 | 28.4] 284) 159.7 6. Church, Va. 20.0 | 11.4 72 38. 2 26. DOOR peel 20 | 10.3 97. 10) etna ah MORE es tena gers GOP ss See a June 21} 1,000} 17.5 | 28.7) 241 | 135.7 le LEO le 64 | 34.0 29. 17.5} 1.9 25 | 12.8 78. Red raspberries: Cuthibentie. Je. s2 2... Anne Arundel] July 2] 1,000] 19.5] 30:8] 311} 176.4 5. County, Md. 19.8 | 10.5 SN | Pe 36. PAV Ah PA 22))\ Tae: 87. Blackberries: ~ Eldorado, first day’s run..| Maryland......... SULy a) OOOH else al es0hon 222 elo barr 8. 18.5 | 10:2 60 | 31.7 31. Uy Pale 22) 11.3 88. Eldorado, second day’srun.|--... GOsseesemee es July 8] 1,000] 26.7 | 30.8] 239 | 135.5 ds 25.8 | 9.4 55 | 29.0 34. A Dore ple “18 9.2] 108. VV AIEEE Sere aps men se a ote me SRR at CG NEL OB 03 28 Le Oe June 28| 1,000] 16.8 | 29.0] 274] 181.8 5. eee 10. 9 58 | 30.7 32. Red currants: : zeit ae eS Fay, first day’s run......- INOW; OnK2 2-2 2- July 16} 1,000] 24.1 |} 30.2 HOn alan d Sie 23.9 | 11.8 13 6.9 144. 24.5 1.8 7 3.4 294.1 Fay, second day’s run.....|.....do..........-..| July 17| 1,000| 24.1 | 29.6 48 | 27.1 36.9 24.1 9.1 10 5.3 188.7 24.5! 0.8 5 2.6! 384.6 ao = a Ss) Las Sees ot Nes |__J_ Lice aaheaeke “SG TURPE—DEG, TEMPEFA Fic. 4.—Fffect of temperature on the rate of respiration of blackberries, currants, huckleberries, raspberries, and strawberries. —_- VLES CENTIGRADE —ll. (To face page 13.) 95678°—Bull. 142 14 STUDIES ON FRUIT RESPIRATION. TaBLE 1.—LEffect of temperature on the rate of respiration of fruits—Continued. Kind and variety of fruit. Locality where grown. Black currants: Burst Gay7s Tun: = 6-2 - es = Geneva, N. Y..... Second days Tun=.22- =25-4|-222 GO-- 2822 2245s Phinrdsday7S RUN: <5 see GOrs so ae Huckleberries: GOUIAUSSACIGDUCCOLG aa ee eee eee | Peaches: Carman, hard-ripe....--..- Americus, Ga...-- Carian sri pened aaa es =| eee dos Wot tet aS So es es dow are ETE yokes 2 seo anne Fort Valley, Ga... Cham pion-~. sae ase Arlington Farm, Va. Connett, first day’s run....|__._- do... Connett, second day’srun.|__... doze: ID eria See san ese seein aoe | See GOStess see Plums: AAS ad Lada SS Ace er capstan a! Nese do--: GOT eee seme eee eae GO:dt eee s Damson Tere eae eee | Washington, D.C. Pears: | SeCkeliaas: Mapes sig eae SOE ae | Takoma Park, Md. Kietieny eee a ae ne Arlington Farm, Va. Apples: J OLLOTISS Aa carrey eae et a ea College Park, Md.. Summer Pearmaina ses lee dose ee Yellow Bellflower.......-. Watsonville, Cal. . Fedak earmain a aes fs mehr GOS eee yan Missouni Pippin. .o. 55. c lc 20 dose ebees — Date received. Aug. 4 June Ai une June July 6 Aug. July 22 July Aug. Aug. Aug. 10 Aug. Aug. 22 Sept. as - 19 83 Carbon a dioxid. Bn $ 3 n 4 5p Blgs |ae. ay SES ome 5x o- js 190.5 56 Sy 1S. 4 oO Tw: =a 3 tom: 3 S Fes [sad eae alse epee Oo ma Pes) & |B S| ees Dag o |IS9oao § Ss Seog oD 2Oos| 5 5 a5 | SS & = < > Hours.| °C 5 Ol ole 139 | 78. Ube Sy |} We 28 14. 24.1 | 30. 136 | i. Pee |) ies 29 1s 20.8 if 9 4, Paty | alls 163 92. 73 G) | 1 28 14. 24.2 ie 9 4, 623 oO: 84] 47. 6.8 9. 23 12 6.6] 0. 7 of Sl PERI OTE 120 67. 17.5 | 10. 20 10. UC if 8 4, 16.8 | 29. 134 75. 17.5 9. 28 14. 17.8 if 11 Sy PAtsy || Qube 134 76. 24.2 8. 22 itil 24.3 0. 9 4, 16.5 | 29. 114 5: 16.8 9. 19 10. 42.8 | -25. 84 46. 42.4 as 13 6. 42.9 it 7 3h 23.9 | 29. 104 69. FALE I PAS |) 18) 24.3 7 3 ATaGn|n2 93 52. 47.8} 1 ee tite 47.5 6 ae 16.8 | 3 106 60. 2 40. 10 WOON CON OHO OOM PRN OHO OOMPODW WHEN ANOR B® NORMHORDRFHMOWFRNCONOPERONWDON Ola WON ONNWONN. He ie) 0. i 9: ike i 2. 16.9 | 26. 73 18:8} 9. : 18.8 | 1. 7 3. 21.3) 27. 69 | 38. 20.9 | 12. 1) |p uae 21.3) 1. 6 3. 28.3 | 30. 103 | 58. 28.51 8. 10 5. 28.5 | J. 6 3. 23.9 | 26. 44 | 24. 24.0 | 10. 10 5. 24.6) 1. 5) 2. 2051} 26: 23 | 12. 20.4] 7. 5 2. 20.3 | 0. 3 Us 24.7 | 34. 50 | 28. 24.7 | 22. 19} 10. 24.3 | 10. 11 5. 24.6 | 2. 4 2. 22.5 | 27. 46 | 26. 22.5 | 10. 13 6. 23.8 | 26. 46 | 20. 23.7] 8. 13 6. 23.5} 1. 4 2. 5.7 | 34. 65 | 37. 14.7 | 24. 30 | 16. 14.6] 9. 13 6. 14.7] 2. 3 12 14.8 | 34. 50 | 28. 14.8 | 23. Zila eats 14.8 | 10. 11 5. 15.0 | 2. + 2. 21.3 | 20. 29 21.3 | 10. 12 ZU ok: ired for fruit to _ carbon equal to its own volume. Time requ dioxid evolve 94.3 iy) 6 — NPN R ODN SO bho ft F100 HL STO Sebeliciey ciao eei Ces 100.0 EFFECT OF TEMPERATURE. 15 TaBLe 1.—Effect of temperature on the rate of respiration of fruits—Continued. : é : Locality where Date Kind and variety of fruit. orn. ene ng Grapes : 1910. Black Cormichonss-es-ee2 Califormia 4524.52. Oct. 5 Flame Tokay, first run....| Clements, Cal... _. Ochi +6 Flame Tokay, second run..|...-.- GOL Ss Saas Dae Oct. 6 SOOANIN CLL itp Se Bee spas Poy] 02 1310 ae ny See a Dec. 1 JAINESS cs Sere een ne a Wiillande IN. ©3222 Sept. 9 WMelawaTreneon sess ol eee Arlington, Va..--. Aug. 29 Concord 2 535 eo ee ee Penn Yan, N. Y..| Oct. 20 INGA ATS. ah ye Pee Ue New York........ Oct. 21 Catawibalssastce meets nek ales. CO SR Beas Oct. 22 Oranges: Valencian late sara sss a eee San Dimas, Cal. Aug. 15 Lemons: Eureka, partly green......|_-- Coe ae meee Aug. 13 Kureka, fairly well yel- |..... COEES BAe Se Sines Aug. 14 lowed. Pineapples: IRGC! Syopmanisin sg. oo5 ke Walkonaren Gol Bys oo LS Aug. 3 Smooth Cayenne, first | West Palm Beach,| July 28 day’s run. Fla. Smooth Cayenne, second !..... GORE eee July 29 day’s run. ‘ Mangos: RuUTpeMtine +225. seen Mice Rae epee Sept. 10 Japanese persimmons: achive sc |. pee Dinsmore, Fla....} Sept. 23 MRane=nashiies 5: ee | Na Cie Sees See Sept. 24 33 Carbon £3 é = dioxid. |#o¢% Pale. BS E D 4, ie Re Te gap See ee lea she} s Ona Goal ee eats aa B la lo s|acs 3s BP Ea |Sesiesa OT ewe cad (ee ion treloees ; ees o |prm. DAI Dar ~~ Bo 3 Py) S da} vo oh aE a y @ |pe8| & |BLSISS8|o08 @ |S8e! £ |gasissh| 85s = 18 < Ei = = Grams.|Hours.| °C. Hours. 1,651 G7 MN BEG PA 46 26.4 37.9 1, 676 24.0 | 21.3 22 12.1 82.6 3, 457 Tre Wass? 9 4.8 208. 4 3, 570 Ved PAB 3 155) 666. 6 1, 5386 ey |) BLY 57 BY4, Uf 30.6 1,523 5.3 | 25.9 24 13. 4 74.6 1, 5389 at WG 8 4.3 232.6 1, 500 5.7 1.8 5 2.6 384. 6 1, 5386 17.4 | 34:2 55 Ball, 31.8 il, SR (eA 265 29 16.2 61.7 1, 539 17.4 | 10.0 7 Bi 270.3 1, 500 17.4 1.8 3 1,5) 666. 6 I AAS AGO PDO Sut reel! ce oes 1,113 16.0 | 10.1 to) | (ae rnee era essen = 1 113 |) 211) 919 ), | OS aia sed 1, 056 16.7 | 34.3 60 34. 4 29.1 1, 130 16.8 | 27.2 33 18.5 54.1 1, 133 16.9 9.3 8 4,2 238. 1 1,138 17.0 Oe 5 2.6 384. 6 1, 224 UG. 7/ |} Bee 86 49.3 20.3 1, 246 16.6 | 27.0 48 26.9 Bila 2 1,110 23.6 9.8 13 6.9 144.9 1, 087 23.8 1.4 4 Deal A476. 2 1, 240 17/533 || e4. 118 (i ¢f 14.8 1,356 OB Ga || PRY 1 60 One 30.1 1, 451 20.4 | 12.7 22 iil, 7 85. 5 1, 214 20.3 Pa, '5) 6 35 Ut 322.6 1,791 17. 6 | 34.2 102 58.5 ilefennle 1,714 17.6 | 22.9 48 26.5 Blo Th 1,781 20.2 } 12.3 14 To 183}, 33 1, 890 PLE iL 2.4 6 oul 322.6 1,613 16.8 | 34.2 101 57.9 U7/583 1, 591 G3") Palle I 32 17.6 56.8 1, 532 16. 7 9.5 8 4.2 238. 1 1, 530 24.6 5 9, 5 2.6 384. 6 2,025) 23.1 |(29.3)|) 2341 13:0)1) 76.9 2,105 P4335, 9.0 4 BAL 476. 2 2, 226 21.4 iL, 7 2 1.0 |1,000.0 2,004 | 30.8 | 29.3 20 1133 88.5 2,020 30.8 Sacto ro 1.6 625. 0 2,080 31.0 War7/ 2 1.0 |1, 000.0 2,005 11.3 | 28.4 i7/ 9.6 104. 2 2,003 11.4 9.7 4 PAS IL 476. 2 2,033 ils 7 67 D, 1.0 |1, 000.0 2,319 1875) |) 3152 104 59.0 17.0 2,479 18.6 | 11.1 12 6.4 156. 2 2, 536 18.5 iy 7 3.6 277.8 1, 754 PAS IN BS it 60 33.9 29.5 1, 652 oe |) 1D) 8 4,2 238.1 1,017 26.3 205 5 2.6 384. 6 1,754 21.9 ! 30.0 50 28.3 8359.33 1, 652 21.9 8.6 7 3 270.3 1,017 22.0 2.4 6 35 I 322.6 930 23.8 | 34.4 192 | 110.2 9.1 794 Deen || 2ihere 123 68.9 14.5 955 PB Bs 8.2 18 9.4 106. 4 873 DOM er etes 6 3,1 322.6 828 23.9 | 35.6 44 Deo 39.5 843 23.9 | 24.0 25 13.9 71.9 953 23.5) || 1053 10 3 188. 7 892 23.6 2.9 3 ilo & 666. 6 1,044 AXA | 30.6 | Lok 17.9 55.9 1, 146 42.4 | 25.0 34 18.9 §2.9 1, 200 42.4 8.5 6 3.2 312.5 1,054 42.3 2.8 2 1.0 |1, 000.0 1 Two days later the rate decreased to 23 mg per kilogram per hour. 16 STUDIES ON FRUIT RESPIRATION. , 9 baal ae ees a = CECA TREC SMREEE: RACY eer oe SRY COMETS WSR EY ia i YANWAA\ SSSSSSSR8\\\:\| SSRSRR eA! SoeeReeeee\\ Pat Pa eae Hee Eee eeeie |. BEREGGGEESE | ce Pada al ee Bethe Ree rees BHR Se eRe TE. ERR eSe eae. . BRREBe. Ser a = TEMPETRAT UFRIE-DEGIRPEES CENTIGIPRADE Iria. 5.—E fect of temperature on the rate of respiration of peaches and apples. re ae =—e EFFECT OF TEMPERATURE. CEE NE eor TEN paler ea ae Ga Rec, a a CON TEE Tey %) 9 ) N iN % MY +) N N e N N Wy SY N Ny) as 8 N “ g S y Q ~ S g S 9 8 9 & &< ss RB Sok sa Sek YPNOH AFA WEEDON! LIS SINCE S/TUM AXOIG NOFAFS 95678°—Bull. 142—11——3 TEMPERATURE -DEGREES CENTIGAADE Fic. 6.—Hilfect of temperature on the rate of respiration of peaches, pears, and plums, 17 18 STUDIES ON FRUIT RESPIRATION. =f RIA" Finer] E. GR dita cha 4O 1 12 13 (4 18 16/7 18 19 20 2/ 22 23 2A 25 26 27 28 29 GO 3/ G23 FAQS TEMPEMATURE~OEGHEES CENTIGHADE "Sn ak ec a 7, 6 fu le rl aed 9 ese eer 1 SEVEN a SEE HEE : : — a 6 abil ihel saa aa ed ® iz | . Pe ae alae A gee © O79 Ss SSsssSRBRRSSE SN GNOH Fae WELDON YFoS SWEYS/THLY : “QIXOIG NOGAFO lia. 7.—Efflect of temperature on the rate of respiration of grapes. EFFECT OF TEMPERATURE. oe es gat flashed os PAG dhl ole CN Bacal aaa 5 (0) = apoE 5-EURETA 12 13.14 (8 16 17 18 19 20 2/ 22 23 24 2S 26 27 28 29 90H 32 33 34 3 ieee HENCE aaa CEE aN Vy 2hhsseee CEES EERE A | EEE = ae TEMPERAT URE— DEGREES CENTIGHADE Fig. 8.—Effect of temperature on the rate of respiration of lemons, oranges, persinimons, mangos, and pineapples. Gf 910 4 Bt gata wae x: jaxagore SoaSSGHSSREERSEER§ | soca rir: SaSmeaE | ~ melanie mene eal sad ola MM BEER EEE S 9 S38 R Se gercgeeesgggsagss ~ OH “— See Yd SWEPADITUIN— G1XOI7 NOGHFD 19 20 STUDIES ON FRUIT RESPIRATION. As was foreseen from the study of the literature, a rise in tem- perature was accompanied by a very rapid increase of respiratory activity, and, as the data accumulated, the general resemblance of the curves to each other became increasingly evident. There seemed to be some general law regulating the increase of respiration with temperature. At this point, material assistance was received from C. S. Hudson, of this bureau. The curve under consideration at the time was that of Delaware grapes. The values at the four different temperatures are given in Table 1 and graphically represented in fig. 9. At Mr. Hudson’s suggestion, besides plotting the actual values found for the carbon dioxid per hour per kilogram of fruit, the loga- rithm of the carbon dioxid figure was used, and the points were found to lie nearly in a straight line. The equation of this line by con- struction is— log (CO,),=log (CO,):<0° + at or if (CO,);=y and (CO,):-o° = Yo, then log y=log y, + at. (Equation 1 :) Logarithm y, and a‘ may be readily determined by inspection ;? log y, (the intercept on the y axis) equals 0.78, and 30a equals 1.790 — log yp, equivalent to 1.010, therefore a equals 0.0337. The location of the straight line most nearly representing the facts is more or less empirical and a number of circumstances must be con- sidered. A small error in the determination of the activity at low temperatures affects the results when plotted as the logarithm much more than the same numerical error at higher temperatures. Hence less weight should be given to the cold-storage values than to the others. With many fruits the activity has been found to decline when held at high temperatures. For this reason less consideration should be given to the data obtained at incubator temperature than to those obtained from fruit kept at refrigerator and at room tem- peratures. While certain imaccuracies are thus unavoidable, this method of expressing the results has been found of great value in comparing the different fruits with one another. The results obtained by plotting the data in this way are given graphically in figs. 10 to 14, inclusive. 3 From equation 1, written in the exponential form y=y,10%, it is. possible to calculate the number of times that y will be increased for any given rise in temperature. If the activity is y’ at temperature U’, at t’’ the activity y’’=y’10@’-. If #’’—#/=10° C., y’” =y/10". The number whose logarithm is 10a is the number of times by which the activity is increased for 10° C. 1 The constant a is defined on p- 24. 2 See fig. 9. ce se seeekes N Ss Se aGeeSeeheR se” ° Sri as messes ys tte pine momar) nin gi wet GSDOWH Saas .G/XOK VOOa | ANOHM 43f NWCADOWH YIS sigegs ua’ a ae WHLIGSYV DOT A ‘a Sie GD/XO17 NOGYFO 95678°— oie Fl ll Sa ais ia Ab Sia Ea a Fa I FT Pp 70 HW 12 13 14 (5 16 /7 (8 19 202! 22 23 24 25 26 27 28 29 FO W Ga FW GAGS HEGGSen Base Sige nie caidas dae PeSesrenaennc: Migiestsc | ieee BEES eee DEREEER ER SS SRRSES ER S S26 Ue x 202/ 22 23 CENT 1 OF. 9 181. 10) 12 13 14 18 16 17 Se Sa eS (SRO 45g NEWS OTY HIT AXOVI NOGZFD> fa) LE GFHEED TEMPERATURE 4 Fig, 0.—Data on the respiration of Delaware grapes, showing the evolved carbon ®ox!d plotted directly and logarithmically 95678°—Bull. 142-11, (To face page 20.) No. 1. = ee eo lia a catiate: aaa erg come et i is ees a tay! ye < ‘ 3 =" g 3 ot 4 : an fh J > —— wie | : nN i $ } ‘s rr Berns poi a ~ tp . i ; a ee i Y carn lehderrtiehiet heed Seidel ‘ r ’ 4 3 = Se vee ‘ t t Loreen ee tp diet ~ fergie ic “RE ES eee Mme ole ton mae me obs weet de es (eo — eee wey te ENS Sree, SEA UNS Tea 7 . 1 aon ‘ ven : 3 aed ; x , wo: ne Sti em ey ie cbc) MoS 9 ARS ER Rae Hare 3 area § ses drdacsdectein ie -ce 3 ies vr e * ia | 7, PX lige ne i | ee oe ee 2 > E i. * 4 f if Lae es ae eR + ¥ r ‘ ' . ‘ ; 2 ae / i . < Lays o ; t . . ‘ 0 + : i a ; ry ‘ : % + ; ae D . b r h , . / . 1 ' ae : —_ . ~¢ we i Z i i ; : . 4 1 u 2 mi r ‘ a ‘ oy A ; or “ey ' P 1 t ib, jon) ‘ , , ; , ¥ ; ys 7 ve a i - - " ‘ j ) ‘ * - . 7 “ j “ - , 7 ii o Ce. 4) re y ba , a a 3 a d ¥ ' ’ e s i A A * ‘ ’ aor ‘ a : i ~ _ a it Py ; - on 7 ; ee o oF <— x bd i ie) ‘ ' i ; rr ®, f Fs = ; : : fen ' P a f MATT ear b c ‘ 7 : v n ig ‘on ; i ’ ” ’ 7 ' rae F : A _ i ‘i : 7 au ! » : : 1 } , 1 7 aed ts : \ vey / ie 7 * aS F e ’ ' ” ‘ . - 7: . Oe 8 i m4) i : t ye av + = . i fl 4 1 " o a [ a i ' { 1 . 7 4 % v F a é 1e, t © | { = . \ * ue x ‘ te P 0 ‘ \ : : ‘ \ ' ‘ ‘ 7 on ; 5 ul 4 ' ’ ; *<) ~ ee i ‘ ) % p e = ~ ' ™, i a a = ‘ i — a J % rf ~ t " ‘ . ees eee A SSSR EERRE. i AI pt pele ee Gat Gis ae NUNS CENT VEN GaawW REN al EN fel ara TAN CHEE iat aN Bo oe eme FEELERS SSDS 3g. TRATUPRPE-DECFPEES CENT/IGHADE TEMPE? Fi@, 10.—Effect of temperature on the rate of respiratfon of blackberries, currants, huckleberrles, raspberries, and strawberries, plotting the carbon dioxid logarithmically. 12 13 /4 18 16 17_/8_19 20 2 22 23 2425 26 27 28 29 GO 9 04 eae (elsiciiaeale als © ) ¥ APACER MLL peal Wea: bo ee Ss POA AIS WESSON AID O/KO/O NOSED > LVELLISS PDOTF No. 2. (To face page 20.) 95678°—Bull. 142—11. : | } 25. a 5 + = : — a Was - ae bik cat es fo osuta 36, “ ~ 4 vt ta tte! oakger’ SA f A@ievedfaeed harmo slnediogid + ~ | ren shan as : aoe: eS eee SR BEANS RNC BON, me tp ! y H - | eel SmI ei deieanin a_i ceeieadtnaineeiande caliente amine emicateaars Cdk - oes eae ee cee EE ee es ee cl de wate? To: bf flnti-* o & ‘ EFFECT OF TEMPERATURE. oe ae , Ale pt Nate Ae ee N\ NCONREEHHE su an \GRSEESBEE A Me ale al kha li 1 Ee a a May po RCAC ECCI \ AKA i lle a ll bt | fA al saan ia Oe SP ae 9S bel pee 8 TULISSTLSTIRTARSAS N WN 21 Fig. 11.—Effect of temperature on the rate of respiration of peaches and apples, plotting the carbon dioxid logarithmically. 22 STUDIES ON FRUIT RESPIRATION. bERBENGGRROREE Ge PCCP aa | NEGSUSGRCReE oo. INCL TE ee BURBGNBABRE MAE oi a: se Paha Vt aia SACCCEEEEEE as S98 \GLY ase SOOO NACE Eee a ON Re AEE ee NGW@ aia ae WN De aA a PIE | wa WEY ALR COCA Cee SRSRSRA NE Sam im Reels feeding | CECE EEE RMS SEe Orb ca ia. 42 13 (#4 15 (6 17 18 (9 20 21 22 29 BF TEMPEKAT USE -DEGHEES CENTIGHAOE MG. 12.—Hfiect of temperature on the tate of respiration of peaches, peas, and plums, plotting the carbon dioxid logarithmically. 4/4 40 mmmmmiaie cc WAG mE ECE CEE ELEN COC RE 98 29.072 S Ss SLSSSS SC SSW sg §s SeRERL YSNOH &f Fa APAOSOTA ela O1fXOIG NOBEFD SO AHLIAPISOT EFFECT OF TEMPERATURE. oo o> 9a Se ae Aw ere | cee mmeree Wis Ca A a NAA ea ea aN Bree he IDE eee: RN ae Pata ald a a a es We a < fe i eee eae a Dee ks ei [icra oleae Deol ime Ue a Ch es \ ila A : oa es ioe a ea ef SEN ee mee pee Ne pote ee ob to WN Eales pa ea pies con Be pallies aes AAA EE dis MW AA AKC = Pais WN bie | ae CHOC ers TEMPERATURE — DECFEES CENTIGHAME iiq@. 13.—Dffect of temperature on the rate of respiration of grapes, plotting the carbon dioxid logarithmically. a © f 5 EEE Ae SESSRSSEeR Wa Semen SSRSSRRS08.% Gene EEEEECEECCNNANK CCE Pee ENN CE PECCEEECCLEAN A aE oe: PELE OLIN NAL Le Fe eeeeess\\ CG COC AN ENTE CCC PERE EECA HE 10 +4 42 13 14 15 140 23 24 STUDIES ON FRUIT RESPIRATION. It is also possible to calculate the range of temperature through which it will be necessary to warm the fruit before the activity is doubled or changed by any other factor. If the activity is doubled— y"’ = y/10ale"” NET} ry tt an J Sige tg inne Raley a In Table 2 are given the constants derived by inspection from the straight lines drawn among the points determined by plotting the logarithms of the carbon dioxid formed per kilogram per hour. Logarithm y, is the constant for any special fruit, and the number corresponding (y,) is the calculated respiratory activity at 0° C. expressed as milligrams of carbon dioxid per kilogram per hour. The constant ais a more general constant, changing slightly from one series of determinations to another, and is the rate at which the logarithm of the respiratory activity changes per degree of rise in temperature. It corresponds to the constant A of unimolecular chemical reactions in which the independent variable is time. The number of times by which the respiratory activity increases for 10° C. is also given, as well as the temperature intervals through which the fruits must be warmed in order that the activity be doubled. TaBLE 2.—Constants determined by inspection from figs. 10-14, the increment for 10° C., and the temperature increase required to double the activity. | Temper- | ature Incre- | merease Kind and variety of fruit. Log Yo. | The a. | ment for | required 10°C. | to double | the ac- tivity. 1 i Strawberries: Mariin’s New Queens... 2). 2-2 3 ee eee 1.240 7.4 0. 0366 | 2.32 8.2 GanG ys 22st ee heresies eee ee 1.250 17.8 0365 | 2.32 Se2 Black raspberries: Ransas® 60h Se Ee eee ee 1.357 | 22.8 . 0408 | 2.56 7.4 02 2 = tee Pees ae eee ee ee eee 1.390 24.6 - 0357 | 2.28 8.4 Red raspberries: Gruber esse se ee fee ae Pree or |} 1.310 | 20.4 0384 2.42 7.8 Blackberries: | | | Hidorad0... asshole ES 1.550 | 35.5 0277 1.89 10.9 Dos si) Se eee ets ae ee | 1.420 | 26. 3 | - 0320 | 2.09 9.4 LUE age eine ier, See ee eee ee a oe See So 1.320 20.9 0390 | 2.45 7-7 Red currants | Pa yos tee ee ee ee ee -710 5.1 - 0344 | 2.21 &.8 Deseiesisevss te ee eee oe - 690 4.9 . 0336 Fi 9.0 Black-currants:. 32 3.08 5 Pee ee | 1.060 12.0 . 0347 Baa? 8.7 CR ES Ros SiMe 8s) ACs ye SS | 1.080 11.5 L0g413| 2 2:19 8.8 Huckleberries: : | Gaylusaccia baceata. 2-22" + ee 1.055 11.4 . 5302 2.00 10.0 Peaches: | Carman: (hard-sreen} =f 2520S ee ce . 818 6.6 . 0461 2.88 6.5 Garman: (ripened). 22): 2792 4 3: See Paes eee | 1.070 11.8 | . 0374 2.37 sel i aie Bee ei es Og OT ee 2 ee | 1.000 | 10.0} .0377 | 2.38 8.0 Bisley 22. ss Sg ee ee ee - 895 | 7.9 | - 0402 | 2.52 7.5 champions = 9-2 oo er ee eee | - 800 | 6.3) .0440 2.75 6.8 Connete 2) ep a Pr ee [a g10" | ty ae es 8.4 ‘ WO 2 Se ee ee Se } . 930 8.5 - 0359 | 2.29 8.4 ablberian: = S25 = 2 eee ans ee ee ee - 920 8.3 - 0357 2.28 8.4 Plums: Wrage ks 1925.2 8 2 et See Sa eee - 810 6.5 - 0381 | 2.40 7.9 A oe 5 ase ee Se a es . 655 | 4.5 . 0438 | 2.74 6.9 “ Damsenr’? 22.5 oo. a SSE Soe See | - 610 4.1 .0397 | 2.49 7.6 Wi i) o % N SIN ESN CPYHDON4 tha Fic. 14.—H 95678°- a eee cee ‘ : . ah ater tk . * 4 - eM Ss f° ra eae Ree ao Meee h Te TT a a a eT a aa er] Ss g& SRSRSES 2 a | VV ae if EI EI im i CI ia cE A |e EN SS Sa Ore ESS LOAN | | NAC Ea eh | | tT i ia ciate 5 ata! FIAT, TEMPE? (To face page 24.) 95678°—Bull. 142—11. ig wer mS hace ay' ~) : F mE ca ki fotene- baat ne es an tN ' i; : , es ES ) Sy AOR. > oe - mew} el ! ’ ’ | : $- ree an ste oe bani, i / 4 - rs t 4 ct | : at eo oe memes = ene em amr ne 6 ee rs t t- mh ath veer Pe we - iy — ame rev Siloti ameter = EFFECT OF TEMPERATURE. - 25 TaBLE 2.—Constants determined by inspection from figs. 10-14, the increment for 10° C., and the temperature increase required to double the activity—Continued. Temper- ature Incre- | increase Kind and variety of fruit. Log Yo. Yo. a. ment for | required 10° C. |todouble the ac- tivity. Pears: SOs [Sa Te See ee Aone, See Ee eee BANee 455 2.9 . 0348 Papas 8.7 RG CHT Gr ete eee ee etn ee es oats chee iceneee 510 3.2 - 0350 2. 24 8.6 Apples: AT CLLCSIS Me ee ne eee eee map ree ee eeis 798 6.3 . 0314 2.06 9.6 SummeniPearmaines <2. semanas esac kestebee ae cen 825 6.7 . 0322 2.10 9.4 DVELLOW A BelInOWelne coe reece ce ees ae esaeree -770 5.9 . 0310 2.04 9.7 ICC ER CATM AIM ecco te Soe bee Sen eee ees sige ae . 630 4.3 0333 DANS) 9.0 MUSSOUTIP PID Pineem er emcscree nc see cecrema eee ee - 660 4.6 0380 2.40 7.9 Grapes: GRITS eines hed a ot cpap i Sates Biel ae a teats as SNe eit a pale 580 3.8 . 0349 2.24 8.6 1D YE) G1\,1¢2) 2 ee ee res On DON av ee ey ae ee 780 6.0 . 0337 Pe Ne 8.9 CON CORG re eee ern nateere eta eerie 810 6.5 - 0393 2.47 Hest INT AC ara oe er ok Sarita eyelets Sede Meteo cms 695 5.0 0408 2.56 7.4 COPS TIT G7] OFS VIS tcl aetna ape 2 Ma ate garg to . 550 3.5 . 0437 2. 74 6.9 lam 6 MOka yeocteeis aioe wero eee rae ae eee - 460 2.9 . 0367 2.33 8.2 Os ees ale taser ee Rae ae = See erin! - 485 3. . 0368 2.33 8.2 IBlACk Conmchoma; maa eras sees see eee - 500 3.2 0383 2.41 7.9 SEP AUNTIGRI Mee ete ce ee ee te ect cee . 185 1565 0505 3.20 6.0 Oranges: WalenciaUate)e «ea cecee stones occ len ccc ee kee. - 265 1.8 . 0375 DEH 8.0 Lemons: Une Ka (QRERI) paseo ass te sececs cree ee ence ete - 180 56) - 0381 2.40 7.9 ETRE keh Gy CLl OW) ria eet sarey estes hate lepers bis clatepversioks - 270 1.9 - 0341 2.19 8.8 Pineapples: INGOs Oe Nese oe pees oe eee ae Soe EE moet em ES . 620 eS . 0455 2. 85 6.6 SMOOtMICAVENMeS nase ote Meee oe oe ae eles meters - 430 2.7 - 0448 2.81 6.7 WY Oreo eae a abet giie sts eB ek . 530 3.4 . 0389 2.45 THe tl Mangos: ANURT OTe Ob OVS Ge Seek aye ae an ta ee eae ee Pe tee Ie . 886 Wot . 0430 2.69 7.0 Japanese persimmons: HMA ISTE) CIS eo ee as aD CoE Os CD OR Oe DOeE oeeere - 390 2.9 0450 2. 82 6.7 ACh amerec omer meee icn setae ces memes - 085 3.8 0358 2.28 8.4 ASCE thet eer BOSSI SSS ECE GME NEES HESS OES OSE| ESSA aise ekene samt aa! . 0376 2.376 8.01 DISCUSSION OF RESULTS. Strawberries, variety Martin’s New Queen, were first experimented with, using temperatures of 23.9° and 10.1° C.; 130 and 41 mg per kilogram per hour of carbon dioxid were formed, respectively. Upon inspection of the results of this experiment, Mr. Taylor suggested that a third temperature, that of commercial cold storage, be added to the other temperatures at which it was proposed to determine respiratory activities. Accordingly, in the subsequent experiments a cold-storage temperature was used when possible, thus considerably extending the scope of the work. The study of the respiratory activi- ties of the Gandy variety gave values similar to those found in case of Martin’s New Queen, and the curves expressing the results are practically parallel. Black raspberries, variety Kansas, were found to be intensely active. At 28.4° C. the first lot formed 284 mg of carbon dioxid per kilogram per hour. Blackberries, both wild and cultivated, and red raspberries were also found to be intensely active, the latter forming 311 mg of carbon dioxid per kilogram per hour at 30.8° C. Red currants were relatively inactive when compared with the other small fruits. At temperatures of 30.2°, 11.8°, and 1.8°C., 56, 13, and 26 STUDIES ON FRUIT RESPIRATION. 7 mg of carbon dioxid per kilogram per hour, respectively, were formed. The results of the second day’s run were practically a duplicate of those of the first day. Black currants and huckleberries were intermediate in physiological activity between raspberries, blackberries, and strawberries on the one hand and red currants on the other. Carman peaches when hard-green respired slightly less rapidly than when ripe. After ripening, however, the respiratory activity de- creased slightly but decisively. With Hiley peaches results were obtained at but two temperatures, as the determination at the cold- storage temperature was lost. The curve of Champion peaches closely paralleled that of the Hiley and of the fully ripened Carman. In the case of Connett peaches there was a distinct decline in physio- logical activity from one day to another. During the first day at 29.0°, 10.7°, and 1.1° C., 104, 25, and 7 mg of carbon dioxid per kilo- eram per hour were formed, respectively; while during the second day’s run, at temperatures of 29.6°, 11.0°, and 1.1° C., 93, 22, and 6 mg, respectively, were collected. The curve of Elberta peaches closely paralleled that of Connett peaches during the second day’s run and seemed distinctly less active physiologically than the other sorts. A special lot of Dover peaches picked on August 24, at three differ- ent stages of ripeness, from the same tree at the Arlington farm, was separated by A. V. Stubenrauch, of the Bureau of Plant Industry, into three lots according to ripeness—hard-green, hard-ripe, and tree or eating-ripe. The measurement of the rate of respiration was begun on the same day. The peaches respired at the rate of 101, 98, and 101 mg, respectively, showing that no marked changes in rate of respiration occur during ripening on the tree. The data are as follows: TABLE 3.—Respiration data on peaches picked at three stages of ripeness. Carbon dioxid Xf = . = j i Stage of ripeness. Nun Weight. | Interval. Tempe Sas = ilogram per hour). Grams. | Hours. se Hard-green...---- ES TOE ec Ny ee eM Ae ba gi She 14 1,570 17.8 28 101 lard=ripeess-92" 25-72 Se ae eee aU e CE SAR Ty Hoe 15 1,703 18.0 28 98 PUTCOMTIPOM pace soos See Ne lye ele eel eee es mee 13 1,458 18.3 28 101 Plums, apples, and pears were less active than peaches. Summer apples respired with perceptibly greater rapidity than the winter varieties. 3 The Concord, Delaware, Niagara, and Catawba grapes were found to be distinctly more active than the Vinifera grapes, Flame Tokay, Black Cornichon, and “ Almeria,’ or the Rotundifolia variety James. EFFECT OF TEMPERATURE. DFT. Mangos were nearly as active as peaches. The citrus fruits were exceedingly inactive. No satisfactory theory based on the composition or size of fruits has been found to account for the differences in the respiratory activity. A few moments’ inspection shows that the rate of respira- tion is not a direct function of content of sugar or of acid, and does not depend upon size, as Japanese persimmons are richer in sugar © than strawberries, yet are less active; oranges and lemons, which differ greatly in acid content, have about the same respiratory activity; red currants differ greatly in respiratory activity from black currants, although they are nearly the same in size. Generally speaking, the fruits which have a short growing period, mature rapidly, and become over-ripe quickly—as strawberries, raspberries, and blackberries— are very active physiologically. At the other extreme are the slowly developing citrus fruits, which are very inactive. Intermediate in these respects are the other fruits. Peaches have a shorter life his- tory than apples and are more active. Summer apples do not keep so well as winter apples, and respire more rapidly. In the case of 29 series of determinations the values at the cold- storage temperatures fall below the empirically drawn lines, and it is therefore probable that in cold storage most fruits respire less actively than would be calculated from equation 1, page 20. In 11 out of 15 determinations the value at the incubator temperatures falls below the line, and it is probable that where this occurred the rate of res- piration declined during the period of observation. In general, how- ever, the respective respiratory activities are well defined by equation 1, in which log y,, determined experimentally as described on page 20, is the constant characteristic for each kind of fruit and in which the constant @ is nearly constant for all fruits, varying slightly from one fruit to another. | In calculating the standard deviation and the probable error of the constant a@ from the mean value 0.0376, formule given by Daven- port and Rietz' have been used. The standard deviation equals y7)2 ¥ z= > = 0.00457, where 2D? is the sum‘of the squares o. the differences from the arith- metical mean, and N is the number of observations. The probable error, iygoe ee x 0.6745 = +0.00044, “determines the degree of confidence we may have in using the mean as the best representative value of a series of observations.” 2 1 Univ. of Illinois, Agri. Exp. Sta. Bul. 119, 1907. * Mellor, Higher Mathematics for Students of Chemistry and Physics, 1905, p. 514. 28 -0250 -AH00 0500 Fic. 15.—Distribution, about the mean, of the experimentally found values of a@ (rate at which the logarithm of the respiratory activity changes per degree of rise in temperature), STUDIES ON FRUIT RESPIRATION. The chances are even that the best value of a= 0.0376+ #, and are 4.5 to 1 that it is 0.0376+2E, and 21 to 1 that it is 0.0376+3E, etc.! The distri- bution of the forty-nine determined values of a with respect to the mean value 0.0376 is shown graphically in figure 15. By grouping arbitrarily into classes a frequency curve may be constructed in the usual way. The form of the curve changes greatly, however, accord- ing as the classes are chosen and, as no relation not already well illustrated by figure 15 is shown, the frequency curve is not given. It will be seen that a large proportion of the determinations of a are very near the mean, while the few high and low values are far removed. The results obtained by Clausen? in the study of the respiration of wheat, lupin seedlings, and syringa (lilac) between the temperatures 0° and 25° C. have been cited by van’t Hoff * as an illustration of the fact that the rate of increase in intensity of respi- ration with temperature is similar to the rate of increase of chemical reactions. A rise in tempera- ture of 10° increased the respiration intensity ‘‘2.46 times (on the average) with wheat, 2.45 times with lupins, and 2.47 times with syringa (llac).”’ Similar facts have been developed by Blackman * in discuss- ing the data obtained by Miss Matthaei® in the study of the effect of temperature on the intensity of respiration and assimilation. Here the number of times by which the intensity increased for 10° C. rise has been calculated to be 2.4 and 3.1, respectively. In the determinations of the rate of respiration of fruits presented mn this report the average coefficient for a rise in temperature of 10° C. is 2.877+0.024.° That the respiratory proc- esses of fruits follow the same rule as do the chemical reactions is a fact of great significance, indicating that the fundamental life processes of fruits are chemical. 1 Davenport and Rietz, loc. cit. 2Landw. Jahrbucher, 1890, 19: 893. 3 Studies in Chemical Dynamics, trans. by Ewan, 1896, p. 126. 4 Annals of Botany, 1905, 19: 281. See also Nature, 1908, 78: 556. 5 Royal Society, London, Philos. Trans. 1905 (B). 197 : 65. 6 Calculated as shown on page 20. The quantity +0.024 is the deviation due to the probable error of a. GS pe pee Hr II. EFFECT OF PICKING ON THE RATE OF. EVOLUTION OF CARBON DIOXID BY PEACHES. In the discussion of the rate of the formation of carbon dioxid by fruits Mr. Taylor suggested that experiments be made on peaches in the orchard to determine whether or not they received a stimulus on picking which would be made known by an increase in the rate of evolution of carbon dioxid; by measuring the rate of change an idea of the magnitude of the stimulus to the life processes might be obtained. Field studies were accordingly made and facilities were provided at the Arlington Experiment Farm, where valuable coop- eration was given in the conduct of the investigation. So far as known no data are on record of similar studies. APPARATUS AND METHOD EMPLOYED. Pure air was run through a jar containing peaches attached to the trees and the amount of carbon dioxid given off during a known period contrasted with that formed by peaches at the same stage of ripeness after picking. The jar which contained the attached fruit was provided with a split cover which could be fastened together air-tight by means of long screws after it had been taken apart to admit the branch. The joint between the branch and the cover and the joint of the cover were made air-tight either by use of grafting wax or a specially prepared rubber compound used by electricians. The large perco- lating jars used in experiments 1 and 2 were fitted with brass collars provided with threaded bolts and thumbscrews by which the covers of paraffined hard maple were brought tightly against a rubber gasket at the edge of the jar. The jars were screened from direct sunlight to avoid the rapid rise in temperature due to the ‘‘greenhouse”’ effect; and in order to keep both lots at the same temperature because of its marked effect on the rate of respiration, they were kept near each other under the tree at about the same height. _ IL. J. Briggs, Bureau of Plant Industry, assisted in designing these covers and having them made. 29 30 STUDIES ON FRUIT RESPIRATION. The air entering each jar was purified by passing it through a glass tube, 35 cm long and 5 cm in diameter, filled with soda lime. It was then drawn through a bottle containing baryta water and into the jar. The tube entering the container terminated near its cover, while the exit tube reached nearly to the bottom. The air drawn from the jars passed through a Reiset absorption apparatus, then through a wash bottle containing baryta water and to a suction pump. A failure of the soda lime to remove carbon dioxid from the entering air would, of course, be shown by the appearance of turbidity in the first bottle of baryta water, while the last bottle of baryta water would reveal a failure of the Reiset tube to absorb the carbon dioxid completely. In three experiments, the results of which are detailed on page 32, these bottles indicated that the air was properly purified and that there was a complete absorption in the Reiset tubes of the carbon dioxid formed by the fruit. The air was aspirated through each apparatus at the rate of about 2 liters per hour and was conveyed in glass or copper tubes, avoiding use of rubber tubing as far as practicable on account of the recog- nized selective absorption of carbon dioxid by rubber and because of the marked tendency of much of the rubber tubing on the market to develop minute cracks when exposed to the weather. The carbon dioxid was estimated by the method employed in the study of the effect of temperature on fruit respiration. (See page 11.) As a good many difficulties were encountered during the progress of the work, only three experiments were completed. It was hard to make the joint air-tight between the branch and the jar, and the percolating jars cracked at very inopportune times on account of the warping of the covers. One of the jars cracked during experi- ment 1. In experiment 2, as no other percolating jar was available, a tubulated desiccator was substituted, in which the picked fruit was held. In experiment 3 a large museum jar with a cover made of hard rubber was substituted for the percolating jar for fruit attached to the tree. It was planned to support both jars under the tree on tripods, but these proved not to be sufficiently stable, and the jars were therefore attached by means of universal clamps to half-inch vertical iron rods, the sharpened ends of which were driven firmly into the ground. Only sound normal fruits from the same portion of the same tree were selected. The foliage was carefully trimmed away from the group of fruits selected for inclosure in the jar while attached to the tree. The detached fruit was weighed at the beginning of each experiment and the attached fruit at its conclusion. eee EFFECT OF PICKING. 31 RESULTS OBTAINED. The data of the three experiments are shown in the accompanying table (p. 32). Experiment 1 on Mountain Rose peaches was started in the after- noon of August 10 and finished during the forenoon of the follow- ing day, an interval of 182 hours. Five peaches weighing 325 grams attached to the tree gave off 0.572 gram of carbon dioxid at the rate of 94 mg per kilogram per hour. Five peaches weighing 297 grams detached from the tree gave off 0.497 gram of carbon dioxid during the same period at the rate of 89.5 mg per kilogram per hour. As before mentioned, the jar containing the fruit attached to the tree cracked during the experiment, and slight contamination due to carbon dioxid from the outside air probably occurred, accounting for the higher values obtained. The results of the experiment are, therefore, somewhat inexact, but indicate that there is no marked acceleration in evolution of carbon dioxid due to picking. The results of experiment 2 showed that five Mountain Rose peaches attached to the tree and weighing 312 grams gave off 0.462 gram of carbon dioxid during 18 hours, the rate being 82.2 mg per kilogram per hour, and that five picked Mountain Rose peaches weighing 347 grams gave off 0.466 gram of carbon dioxid during the same interval at the rate of 74.7 mg per kilogram per hour. At the conclusion of the experiment a very slight leak was found in the apparatus connected with the fruit attached to the tree. This pos- sibly accounts for the higher results obtained. Again, as in experi- ment 1, the results indicated that there is little or no acceleration in carbon dioxid due to picking. Experiments 1 and 2 were started near the end of the afternoon of one day and finished during the forenoon of the next, because it was desired to avoid possible disturbances due to temperature differences which might occur even though the jars were shaded, as it was pos- sible that reflected light and heat might have influenced the tempera- tures unequally. During experiment 3, however, a period of cool, cloudy weather made it possible to continue the experiment during three days. ‘There was no sunshine during the first two days, but during the late forenoon of the third day the sun shone for several hours. j In experiment 3 carbon dioxid was formed by six hard-ripe. Champion peaches attached to the tree, at the rate of 51.7, 55.5, and 79 mg per kilogram per hour, during the three days, respectively. Picked fruit gave off carbon dioxid at the rate of 54.4, 56.9, and 82 mg per kilogram per hour during the same intervals. Again, as in OZ STUDIES ON FRUIT RESPIRATION. experiments 1 and 2, no acceleration in rate of respiration is shown. At the conclusion of the experiment a very slight leak was detectable in each of the systems, but it was probably not sufficiently large to affect the results. The results, therefore, show that if any change in the rate of respiration of peaches is caused by picking, such change is very small and not measurable by the method employed. TaBLe 4.—Data obtained in the study on the effect of picking on the rate of evolution of carbon dioxid. i Time of experiment. | ,; = 2s 8 2 o AO So fe = 5 el alee ae \ES Fs 2 zt] Bese. Se r= Variety and description. Date. a6 = bo 3 ey Sisrs g q Sr tie ty feed gaat pts tebe iors lis |S iS re Bi |S ieee laos SEs au jag Be q r am | 88 ) oo jon, a Sp uh |e Bae eS es ee ae a o q =I 5 o 2° 3 8 3 on Py a ea 5 AS EI al el =a S Sas ire | 1910. ] 1 | Mountain Rose (hard-ripe): August. | p.m.| a.m. | Hours. Gms.| cc. | Grams. Attachedstorirees- snes ae 10-11 3.40 | 10.20 | 18.67 | 5 | 325 | 13.0 | 0.572 | 1.760 | 194.0 Detached: =.5 745 4ecey eres e 10-11 | 3.40 | 10.20 | 18.67 | 5 | 297 | 11.3 . 497 1.673 | 89.5 2 | Mountain Rose (hard-ripe): Attached to tree... 2-5-.--2- 12-13 | 5.00 | 11.00 | 18.0 | 5 | 312 | 10.5} .462 | 1.480 | 282.2 Metachedizss 4". cee 4-2 sete! 12-13 | 5.00 | 11.00 | 18.0 | 5} 347 | 10.6] .466 | 1.344] 74.7 3 | Champion (hard-ripe): p.m. Attached to tree............ LG=17 5} 310))| BS ON E2420 1682589) L552 OOTm pleat toro lead, Detached: etree esse eee 16-17 | 3.10 | 3.10 | 24.0 | 7 | 627] 18.6) .818 | 1.305 | 354.4 3 | Champion (hard-ripe): Attached to tree. ..........- 17-18 |) 3.10 |, 2.00 | 22°83 | 6 | 539 | 15.5 . 682 1.265 | 3 55.5 IDetaAChed: =< Suet 2. eee eeee 17-18 |} 3.10] 2.00 | 22.83 | 7 | 627 | 18.5) .814 | 1.298 | 356.9 3 | Champion (hard-ripe): Attached! to trees 3285 ce ee 18-19 | 2.00] 1.30 | 23.5 | 6 | 539 | 22.8 | 1.0032 | 1.861 | 379.0 Detachedteeea ss as5- 2a ie 18-19 | 2.00] 1.30 5 | 7 | 627 | 27.5 | 1.2100 | 1.930 | 282.0 1 The jar cracked during the run. Higher result possibly due to contamination by outside air. 2 A very slight leak perceptible. 3 A barely detectable ‘eak found in both systems. III. RATE OF ACCUMULATION OF HEAT IN THE RESPIRATION OF FRUIT UNDER ADIABATIC CONDITIONS. CAUSES OF SELF-HEATING. As stated in Part I (p. 7), two attempts to determine the effect of - temperature on the respiration of bananas failed because of the very rapid increase in respiration which occurred, incident to the processes of ripening, during the periods of observation at room temperature. It was observed that the walls of the desiccators in which the fruit was kept became wet on the inside. In attempting to discover the cause of this, the bananas were found to be from 1.4° to 1.9° C. warmer than the desiccators. Attention was thus drawn to the phenomenon of self-heating exhibited by certain agricultural products, many similar instances being readily found. ‘The heating of bananas has long been known to the shippers. Carrots, sugar beets, corn and other grains, cotton seed, hayseed, hay, manure, tobacco, and stover all heat readily, especially if stored when moist and under such conditions that the heat as produced is not dissipated. An inspection of the literature shows that self-heating may be due to several causes. Heating caused by physiological processes prob- ably operates first and raises the temperature to the point at which other causes, enzymotic or chemical, come into play. Oxidizing enzyms are the active agents in many cases. They are, for example, probably the dominating factor in the fermentation of tobacco,’ working most actively at the high temperatures which may have occurred as a result of respiration. The microorganisms also induce oxidation or other chemical changes involving the liberation of heat. Finally there is the chemical oxidation which often supervenes when one or more of the other causes has raised the temperature to the point at which chemical action is appreciable. The final result may then be charring, or even combustion. The difficulties in deciding which of the several causes last named are operative in spontaneous heating are interestingly discussed by Rahn. The operation of the physiological processes in respiration seems to be the general cause of self-heating. As the law expressing the increase of the rate of respiration with temperature is now approxi- mately known, it has seemed worth while to calculate the rate at which the temperature would increase when adiabatic conditions are assumed—that is, conditions under which there is no gain or loss in heat from the outside. The results of such a calculation should be of value in the study of self-heating. 1U.8. Dept. Agr., Report No. 59, Loew, Curing and Fermentation of Cigar-leaf Tobacco. 2 Michigan Agricultural College Experiment Station, Technical Bul. 5, 1910. 33 34 STUDIES ON FRUIT RESPIRATION. FORMULA FOR CALCULATING RATE OF HEAT ACCUMULATION. To determine the amount of heat generated in respiration, it is necessary to know the thermal equivalent of the carbon dioxid formed, which has been assumed to result from the combustion of sucrose, which produces 3.96 calories per gram, when burned com- pletely, in the respiration calorimeter. As the reaction expressing the combustion is C,,H,,0,, +12 O,=12 CO,+11 H,O, 042.176 + 384 = 528 + 198.176, each gram of carbon dioxid is accompanied by the evolution of 342.176 X 3.96 528 To determine the temperature rise, K, of 1 kilogram of fruit for each . gram of carbon dioxid formed, it is necessary to divide by the specific heat of the fruit. Assuming the same specific heat of fruit to be that used by refrigeration engineers, 0.9, H=2.85° C. and & (the tem- perature rise per milligram of carbon dioxid) =0.00285° C. Equation 1 (log y=log y,.+at) expressing the relation between the respiratory activity and the temperature (see p. 20) may be written Yt = Yol0™, (2) in which y; and y, are the rates of evolution of carbon dioxid per kilo- gram of fruit per hour at ¢° and at 0°, respectively, and a is a constant determined experimentally. Let the time expressed in hours during which the adiabatic conditions are imposed =T. During the first finite interval of time 47, e. g., during the first hour after adiabatic conditions are imposed, the activity 1s approxi- mately expressed by equation 2 and the temperature rise by At=ky=ky10%, (3) the carbon dioxid per kilogram per hour being expressed in milli- orams. As the temperature changes slightly during the first hour in accordance with equation 3, the results are not quite correct. The rate at which the temperature rises at the beginning of the interval 47 is evidently correctly expressed by equation 3. Therefore dt = 2.5663 large calories.” eae t dv BOE : 1 t" 1 nA 1 1 = ag fe eae Me ee Ne BENE —at On integrating, T ih us 10° “at Caen 10 a | t’ _ 10-2 —107a0" kya log, 10’ 1 Data from U.S. Dept. Agr., Office of Experiment Stations, Bul. 109, p. 17. 2 The value 2.56 is given as the calorific equivalent of 1 gram of carbon dioxid by Benedict and Car- penter (Carnegie Institution of Washington, No. 126, p. 211). RATE OF ACCUMULATION OF HEAT. 35 enn cama MOR tay trays to 1—ky,a log, 10. 10% 7 er log 1 —ky,a log, 10T) a or pr apr 108 (i-m T) a a where m=ky,a log, 10. The most difficult part of work of this kind is the selection of the differential; this was done by S.J. Dennis, of the Bureau of Plant Industry, who also aided the author in making the integration. APPLICATION OF FORMULA TO SPECIFIC CASES. As an illustration this formula has been applied to the Connett peaches of July 22, which, if they followed exactly van’t Hoff’s formula, would respire at the rates of 120.5, 53.0, 23.2, and 10.2 mg of carbon dioxid per kilogram per hour at temperatures of 30°, 20°, 10°, and 0° C., respectively—the constants a=0.0357 and y=10.2 having been determined experimentally. In the following table the increases of temperature with time are shown: TasBLe 5.—Increase of temperature of Conneti peaches, during definite intervals of time when adiabatic conditions are imposed at varying initial temperatures (July 22). Temperature of fruit (¢’’) after given intervals (7), calculated from different initial temper- atures (t’). Interval of time ( 7). v—O02C: t/=10° C. t/=20° C. H—30 RC: y=10.2 Y=23.2 y= 53.0 Yy=i20.5 m= 0.0024 | m= 0.0054 | m= 0.0124 | m=0.0282 36 STUDIES ON FRUIT RESPIRATION. The same data are given graphically in figures 16 and 17 (pp. 37 and 38). The curves and model show that fruits stored under such condi- tions increase In temperature and in physiological activity more or less rapidly according as they are warm or cool when adiabatic con- ditions are imposed. At cold storage or refrigerator temperatures, in case of the example given, the temperature rose 0.3° and 0.7°, respectively, during 10 hours, whereas during the same interval the temperature rose 1.45° and 3.65° when the temperatures at which the fruit was stored were 20° and 30° C., respectively. It has been sug- gested that it would be possible to follow the rate of temperature rise of a product about to undergo self-heating by placing a recording thermometer near the center of the material. If the heating observed -was due to the operation of the respiratory activities alone, it is probable that the curve drawn by the recording thermometer would approximate the theoretical curve which could be drawn in advance from a knowledge of the respiratory activity. It is thus highly probable that this method of calculating the temperature rise and of tracing the theoretical curve will be of value im the investigation of phenomena of self-heating, the causes and mechanism of which are now but little understood. RATE OF ACCUMULATION OF HEAT. 37 pi ia ial Bail Ant aaees me is at a pees ase pad iMG cen fo a ee Ieee pe rea) eile . a se ser a ean OL ea id a cen a RK ee Cpa ie | eee FT ial nd Sao etalk male Hilde id ce j i aa nat isin) =. ial al Fal aia ei ae Pio aoe i ae Mia iis (ai aes eo mea | ata Lew ese Ba a Fae ae eae aoa eal ie sb Enea Es | st Hobs Flat a ea call a nm 250 Sie (aa a | ee ane POLAT oT (al Clean B ia a C | orien 2/0 pee eal if Sa ig i es ia ae Died foal i fl a