EFFECTS OF ACETYLENE - Plant Physiology · SOME EFFECTS OF ACETYLENE ON THE RIPENING PROCESSESOFBANANAS' R. HARTSHORN (WITHEIGHTFIGURES) Introduction In recent years there has been

SOME EFFECTS OF ACETYLENE ON THE RIPENINGPROCESSES OF BANANAS'

R. HARTSHORN

(WITH EIGHT FIGURES)

Introduction

In recent years there has been considerable in the literature concerningthe action of ethylene and propylene on the ripening processes of fruits.Under certain conditions, it would appear that both of these gases arecapable of hastening the ripening of some fruits, DENNY (3, 4); REGEIM-BAL (28); ROSA (30, 31); and OVERHOLSER (26). Whether the action ofthese gases is due to the fact that they are unsaturated compounds or tosome other property common to both remains yet to be shown. However,acetylene, another hydrocarbon which is even more unsaturated than theaforementioned ones, has been little experimented with in this regard.HARVEY (14) reports it as being unsatisfactory, but does not present ex-perimental evidence to indicate the nature of its action. Any informationconcerning its action on the ripening processes of fruits would be of inter-est therefore, first, because it would be new regardless of whether or notthe action were similar to that of ethylene and propylene; and secondly,if similar, it would tend to strengthen the hypothesis that the action ofthese gases is in some way associated with the unsaturated condition ofthe molecule.

It is the purpose of this paper to present the results of experimentationon the effects of acetylene on the ripening processes of both normal andchilled bananas. It is not considered that this is a finished piece of work,in any sense; but it is hoped that it may be of interest or suggestive tothose now engaged in projects along these lines. The work reported wasdone in 1928.

Materials and methodsThe fruit used in the first experiments was received from the United

Fruit Company.2 It was shipped by express from New York City toIthaca, N. Y., arriving there about 24 hours after unloading in New York.It was the Gros Michel variety and was green at the beginning of theexperiments unless otherwise stated.

1 Presented before the Physiological Section of the Bot. Soc. Amer., N. Y. Meetings,1928.

2 The work herein reported was started during the tenure of a United Fruit Com-pany Fellowship. It was done in the Laboratory of Plant Physiology, Cornell Uni-versity.

467

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PLANT PHYSIOLOGY

The green fruit is very hard. The hardness was measured in theseexperiments by a specially devised instrument which measured the forcerequired to insert a cylindrical metal plunger a given distance into thepulp. In these results, the index 7 indicates a very hard, green fruit;whereas 1 or less indicates a very soft, or ripe fruit.

The starch content of the green fruit is very high, a cross-section ofthe fruit becoming entirely black when treated with a few drops of iodine-potassium iodide solution. In the ripe fruit, the starch has largely orcompletely disappeared as indicated by an absence of coloration with theaforementioned test. Generally, the ripe fruit still shows starch in themiddle and in three narrow bands radiating from the middle of the pulp.These areas, however, are not as black as in the green fruit, and the inter-mediate areas may be completely free of any starch.

S

All samples were composed of a number of individual fruits whichwere selected to be as comparable as possible. An individual fruit iscalled a finger and a cluster of these a hand. In the main experiments,the control and treated samples were composed of halves of the same hands.

The temperatures, though fluctuating in some instances, were alike inall cases in both control and treated samples. In the respiration experi-ments the jars containing the fruit were submerged in controlled tempera-ture baths. The air was brought to temperature before its entrance intothe chambers.

The only differences, therefore, between the treated and the controlswas the presence of the acetylene or carbide. The humidity was high inall cases as indicated by the condensation of moisture on the inner surfacesof the containers.

In the jar experiments, carbide was placed in the bottom of 3.5 literbattery jars and covered with cotton to prevent contact with the fruit.The tops of the jars were covered with a layer of cotton to allow air ex-change while still preventing a too rapid loss of acetylene and moisture.

Respiratory rate was determined by use of an apparatus which per-mitted a continuous flow of CO2-free air. The determinations were madeover two hour periods by the absorption of CO2 in NaOH by means ofmodified Reiset tubes. The residual alkali was titrated with standardizedHCl after the addition of BaCl2 to precipitate the carbonate. The respira-tory rate was calculated as milligrams of CO2 per kilogram of fruit perhour, (C02-MKH).

Preliminary experimentsThe results of a couple of experiments will serve to illustrate the results

obtained in several preliminary tests.

468



HARTSHORN: ACETYLENE AND RIPENING OF BANANAS

EXPERIMENT I

On M~arch 21, 1928, eight firm, green fingers were placed in each of twobattery jars, (3.5 liters capacity). About 12 grams of calcium carbide wereplaced in the bottom of one. Each jar was covered with a layer of cotton.The temperature during the experiment varied from 16 to 24° C. (61-750 F.). The treated fruit began to turn yellow in three days, the controlfruit remaining green. At the end of five days the treated fruit was ripe.It had a good yellow color, medium starch content, and a fairly goodflavor; whereas the check fruit was just beginning to assume a yellowcolor, had a high starch content, and was still inedible.

This experiment was repeated a number of times with different lots offruit and in no case, when the fruit used was green at the beginning andthe temperatures maintained within this range, did the control fruit ripenas quickly or as uniformly as the treated. In those instances in which thefruit had clearly begun to ripen or where temperatures much over 240 C.(750 F.), were encountered for any length of time the differences werequestionable though always favoring the treated as regards the color ofthe peel. On the other hand, in a few cases in which the treated fruitripened well in five days, the check samples were still green at the endof twelve days.

EXPERIMENT II

An experiment was planned to show the relative efficacy of varyingamounts of carbide. As all the amounts used were equally effective, theexperiment merely indicates the difference which may be obtained due tothe treatment of bananas with carbide. Portions of hands, composed ofseven or eight fingers, were placed in jars covered with cotton. Therewere about 2.5 liters of air space remaining in the jars after the fruit wasplaced therein. Amounts of carbide varying from 0.25 to 4.0 grams wereplaced in the jars. Cotton was placed on the carbide to prevent contactwith the fruit. The jars were placed together in the laboratory. Theroom temperature varied from 12.2 to 240 C. After the first two days thetemperature was not above 20.60- C., and was above 15.60 C., most of thetime. The temperatures encountered, therefore, were favorable for ripen-ing but were not sufficiently high to cause its undue acceleration. Whenthe experiment was started, June 13, 1928, the fruit was green in colorand showed a pulp pressure of 5.5. The observations made three, and fiveand one-half days later are presented in table I.

This experiment clearly shows the effect of the carbide treatment, andfurthermore, tends to indicate that there are no sharp limits to the effectiveconcentration of acetylene. The results obtained are the more striking inview of the fact that the odor of acetylene was readily detected several feetfrom the group of jars, including those containing the control fruit.

469



PLANT PHYSIOLOGY

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The effect on respirationEXPERIMENT III

Because a preliminary experiment had suggested that respiration wasincreased during treatment, another trial was made with greener fruit tocheck the observations. The samples were composed of halves of the samehand and each contained six fingers. The treated sample weighed 1,021and the control 958 grams at the beginning. The temperatures were highbut alike for both samples. The air was drawn through the chambers atas near the same rate as possible by comparing the rate of bubbling. Itwas approximately 15 liters per hour. The results are presented infigure 1.

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261 ...... :7-:....Ro~~~~~~~~~~~~~~~~. m.... S.--...77

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FIG. 1. Effect of the carbide treatment on the respiration of green bananas at roonitemperature. Exp. III.

At the end of 120 hours, the treated fruit was excellent in appearance,being uniformly golden yellow. It had a very good flavor, medium starchcontent. and a pressure of only 0.5. The cheek, at this time, was of variablecolor, being from yellow to green. It was not ripe as indicated by flavor,high starch content, and a pressure of 1.2.

The treated fruit ripened quicker, better, and more uniformly than thecontrol. Accompanying this there was a marked acceleration of respira-tion. It was not affected at the first determination, (2.5-4.5 hours), fol-lowing the beginning of the treatment. The maximum difference occurredat 52.5-54.5 hours after the initiation of the treatment, at which time thatof the treated was 3.6 times that of the control.

Effect on respiration of severely chilled fruitEXPERIMENT IV

The fruit used in this instance had remained packed in barrels withhay for two days after arrival and was light green in color. It had an

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PLANT PHYSIOLOGY

index for pressure of 7.0-7.5, indicating that very little if any ripeninghad occurred though the temperature of the fruit at the end of two dayswas 21.10 C.

Three hands from the middle of the stem were subjected to tempera-tures of 4.4-10' C., for 38 hours. Most of the time the temperature wasbelow 7.2° C. The chilling temperatures are shown in table II. At the

TABLE IITEMPERATURES (OC.) DURING THE CHILLING PERIOD, EXPERIMENT IV

HOURS OF 0 1 1.5 2.5 11.5 13.5 20 26 38CHILLING

Air tempera-

ture ........ 12.5 7.8 6.9 6.7 6.9 4.4 7.2 6.7 11.0

Pulp tempera-

ture 21.0 11.7 8.0 7.2 7.2 4.4 7.2 6.7 10.0

end of this treatment the pressure was 5.5. At this time the hands werecut into halves and two samples made, each composed of halves of thesame three hands which had been subjected to identical treatluent. Thesamples were quickly weighed and placed in the respiration chambers.The weights of the two samples were 2,129 grams for the treated, and2,136 grams for the control. The air flow was regulated to 20 liters perhour as measured by calibrated flow-meters. The temperature was closelymaintained at 210 C. The only difference in the two samples was that, inthe case of the treated, the air was drawn over 15 grams of calcium carbideimmediately before entering the chamber. When first opened, at the endof 77.5 hours, the chambers still smelled strongly of acetylene though mostof the carbide appeared to have been used at the end of 24 hours. Theresults are presented in figure 2. At 128 hours the pressure of the treatedwas 0.9 whereas that of the control was 2.8. These were essentially thesame as the determinations at 77.5 hours. The flavor of the treated was

r._.-::..::-:. ::: , r::Am.:.:.: "i ...1.................. A. ! -........ ....

-o 40 60 BC 100 140/40

FIG. 2. Effect of carbide treatment on respiratory rate of severely chilled bananas.Exp. IV.r-trted

IV.---- control

472




fairly good at this time but that of the check was not good even at 203hours. The observations as to color and starch are given in table III.

TABLE IIIRESULTS OF EXPERIMENT IV

TREATMENT COLOR STARCHHOURS AT210 C. CONTROL CARBIDE CONTROL CARBIDE

0 yellowish-green yellowish-green high high59 . "it greenish-yellow78 " cc yellow high medium-high

128 " " slightly pale yellow lmedium-low(no green tips)

203 3 yellow fingers ( high(green tips)

most yellowish-green

The results obtained warrant the conclusions that the fruit was severelychilled and that the carbide treatment markedly influenced the rate ofripening as indicated by increased respiratory rate, (at 45-47 hours afterthe beginning of the treatment, that of the treated was 4.4 times that ofthe control), more rapid softening, loss of starch, and improvement ofcolor and flavor.

Ammonia, an impurity in acetyleneIn viewof the work of BACHER (1) which showed that small amounts

of almmonia in the air stimulated the growth of certain plants, and alsothat ammonia is generally conceded to be one of the chief impurities inacetylene, (LEWES 19, p. 472, LIEBETANZ 20, p. 247, and MATHEWS, 22), itseemed well to test the effect of this gas on the ripening of the fruit. Inaddition to treating the fruit with ammonia, the acetylene-air mixture wasalso purified by a method suggested by MATHEWS (22) which would removeany ammonia present. The resulting gas-air mixture, which was pre-sumiably free of ammonia, phosphorus compounds, sulphides, carbon mon-oxide, and carbon dioxide w-as passed through the respiratory chambers.It is quite likely that any possible trace of ethylene would be oxidized bythe ehromic acid (21, p. 91).

EXPERIMENT V

The purpose of this experiment w-as to determine whether ammonia wasresponsible for the effects previously attributed to acetylene. The fruitused w-as obtained from a local dealer but w-as still green as shown byappearance, pressure, and the respiration curve of the check. Halves of

473



4 PLANT PHYSIOLOGY

three hands were used, and the weight of each sample was in the neighbor-hood of two kilograms. The procedure was similar to that in the previousexperiments. The temperatures were closely maintained at 210 C. Theammonia was supplied as ammonium carbonate, over which air was passedbefore entering the chamber. It was planned to use an amount of the saltwhich would give, if uniformly distributed over a 24-hour period with anair flow of 20 liters per hour, a concentration twice that which BACHERfound to be best for growing plants. It was not expected that the fruitwould respond as readily as growing plants. As the first treatment ap-peared to be ineffective, two addition treatments of twice the originalquantity were made. Comparisons were made with the untreated fruit,fruit given the carbide treatment as previously, and that exposed to thepurified gas-air mixture. The results are presented graphically in fig. 3,

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20 40 6O 80 /00 120 14b4H.sFIG. 3. Effect of ammonia, acetylene, and purified acetylene upon green bananas.

Exp. V.

and a photograph of the representative samples taken at the end of 120hours is shown in fig. 4. The sections cut from the fruit were treatedwith iodine in potassium-iodide solution and show the disappearance ofstarch from the central portion of the fruit treated with acetylene. Thecheck fruit and that treated with ammonia do not show this difference.

At the time these samples were taken, both those treated with acetyleneand purified acetylene were yellow and well flavored, whereas both thecontrol and the ammonia treated samples were mixed yellowish-green andgreenish-yellow and were decidedly unripe. The starch test for the acety-lene treatments was described as moderately high, while that for the checkand ammonia treated was. termed very high. The last two ammonia treat-ments were probably somewhat severe as the final ripening was not asgood as that of the check and also, there were a few very small brown dotswhich were probably indications of injury at the points of entry. Fur-thermore, the divergence of the respiration curves for these two samples

474



HARTSHIORN: ACETYLENE AND RIPENING OF BANANAS

Chc.c AMrnman i RPrie4Aceb}erieAcetIene

FIG. 4. Representative samples from the treatments in Exp. V showing color change anddisappearance of starch with the acetylene treatments.

suggest that the ammonia treatment hindered ripening. From this experi-ment it appears that ammonia was not the active agent in hastening theripening in the previous experiments, as certainly all traces of ammoniawere removed in the purification in this experiment and the results ob-tained with the purified gas are practically the same as those with thecarbide treatment. Undoubtedly, some of the acetylene was absorbed bythe sulphuric acid used in the purification. There was no detectableodor in the chamber receiving the purified gas whereas the other chambersmelled strongly of acetylene. It seems established, therefore, thatammonia, as an impurity in the acetylene. is not responsible for thehastened ripening with the carbide treatment.

Acetylene from another source

DENNY (3), in his work on the coloration of lemons, did not obtain thesame results with acetylene generated by the action of alcoholic potash andethylene dibromide as with that from tanks. It seemed advisable, therefore,

475



476 PLANT PHYSIOLOGY

to test this point in regard to bananas. Acetylene was generated from theabove substances by a method described by SABENEJEFF (32) with theadditional purification suggested by ZEISEL (40).

EXPERIMENT VIIn this experiment comparisons were made between the effects of

purified acetylene, acetylene from ethylene dibromide, and ethylene. Theprocedure was similar to that of the preceding experiment except that thelatter two gases were introduced into the air stream from bottles by dis-placement with water. The fruit used in this experiment had been in a

ripening room with a kerosene stove for 24 hours before being obtained.All samples, including the control, ripened very quickly. The resultsappear in fig. 5, and the observations in table IV.

co,MMH/80

160

/40

/20

/00

80

60

40Zo 40 60 Bo /(flHors

FIG. 5. Showing respiration of rapidly ripening bananas. Effect of gas treatmentson respiration questionable. Exp. VI.

TABLE IVOBSERVATIONS ACCOMPANYING RESULTS OF EXPERIMENT VI

AT END OF 72 HRS. AT END OF 103 HRS.TREATMENT

COLOR COLOR FLAVOR

Cheek yellowish green yellow and slightly slightly astringent(not uniform) greenish yellow,

green tips

Purified acetylene pale yellow yellow, two green goodtips

Acetylene from pale yellow yellow, no green goodethylene dibromide tips

Ethylene.greenish yellow, yellow, no green goodpale Fellow tips

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It is quite clear from the graph that there was very little difference inthe respiratory rate of the check and that of the sample treated with acety-lene from ethylene dibromide. However, considering the differences incolor and flavor, and the fact that the check ripened unusually fast, itseems that the lack of greater differences in the respiratory rate can safelybe explained on the basis that the previous treatment had already acceler-ated the ripening processes. In order to check this point, this experimentwas repeated.

EXPERIMENT VII

Halves of two hands composed a sample, each of which weighed about1,700 grams. The check sample was from the same hands as the sampletreated with acetylene from ethylene dibromide. The temperatures of thelatter treatment were purposely kept slightly below that of the control toavoid any possibility of the temperatures being in its favor. Because ofthe importance of the temperatures in this case the actual data are pre-sented in table V. It should also be stated, that the ethylene treatment

TABLE VTEMPERATURE RECORDS FOR EXPERIMENT VII.

TREATMENT

TIME CHECK PURIFIED ACETYLENE ACETYLENE FROMETHYLENE DIBROMIDE

AIR BATH PULP AIR BATH PULP AIR BATH PULP

hours 0C. 0C. 0C. 0C. 0C 0C. 0C 0C 0C.0. 21.1 21.1 20. 21.1 20.7 20. 21.1 20.4 20.6.5 21.8 20.9 21.9 20.8 21.2 20.68.5 21.9 21.1 22.0 21.1 21.4 20.5

38. 21.7 20.9 22.0 21.1 21.2 20.840. 22.0 21.1 22.6 21.1 21.5 20.672. 22.0 20.9 22.2 22.5 21.4 22.2 21.4 21.178.5 22.2 21.1 22.3 20.8 22.2 21.1 I80.5 22.0 21.1 22.2 20.9 22.2 21.194. 21.9 20.8 21.1 19.4-21.1 21.8 20.496. 21.9 21.1 22.2 21.9 21.1 21.4 21.7 20.4 21.4

in this case is not strictly comparable in that an electric light bulb wasused as a heating unit whereas, in all other cases, immerson heaters wereused. The effect light may have is unknown.

Unfortunately, the fruit used was not satisfactory as it was even olderthan that used in the preceding experiment. The results, fig. 6, indicatethat the fruit was well started in the ripening processes at the beginning

477



PLANT PHYSIOLOGY

tZ0 40 G(' 80 100 Hourp

FIG. 6. Effect of purified acetylene, acetylene from ethylene dibromide and ethylene uponthe respiration of ripening bananas. Exp. VII.

of the experiment. In spite of this, there was a slight but significantdifference in the respiratory rate of the fruit treated with acetylene fromethylene dibromide as compared with that of the control. Also, at the endof the experiment, the check still had green tips while both of the acetylenetreatments were uniformly yellow. The treated fruit was well flavoredwhereas the check was slightly green and astringent to the taste. In viewof these differences, and in spite of the conditions it seems quite likelythat acetylene, from either calcium carbide or ethylene dibromide and KOHwill give similar hastening of the ripening of bananas. The effect ofacetylene appears to be qualitatively similar to that of ethylene.

DiscussionA comparison of the respiration determinations of various samples is

given in fig. 7. The curve, (number 3), which represents the average ofseveral check samples, indicates, in general, the form of the respirationcurve of normally ripening bananas held at 21.1° C. Sometimes the riseis a little more rapid, the peak higher and more pointed. On the otherhand, when fruit has been subjected to conditions which affect it adversely,the curve may remain very flat for some time. This is illustrated by thecurve of the chilled fruit, (number 1). Curve number 5 is that of thecheck in experiment VI, in which the treatments failed to show accelera-tion of respiration. The explanation for this lack of difference seems tobe, that the fruit was already in the process of ripening very rapidly andnear the peak of its activity. To substantiate this, is the fact that when

478




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curve 5.issuermporsedo ueponaicurv 3,e (seekdotte infes),t thperagreements.Ceems to bevrycoe.Crvllsihtnftegotrliexperiment, VII,hile)in which more differmenceiwasc showylnbytetreatmentstIwillebekeseenleathatin Thpiscasiengalsortefruitrase ripeningrapilybucntscaidyss)n.hothercase andtharmet consequhtentlyntshewdolysihdifferences.deth retetwr

Threreoe sic thefruitimusedinocrexp(erientVIteaindeIIwaitheagemnproesms tof riengvery rapidlyurv an netaro thepeakrof its acteivitnt IsInosurprisin tor fidifeecthatowbthe treatments.dinot cause grete aceleration.inthes tcatmelsotsefriapparst bienmost effecivey int shortensraingythe initial

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of activity has commenced the presence of the gas is no longer necessary.This, however, needs experimental investigation. If the precedinghypothesis is correct, then such varieties as the Ljacatan, which are ripenedslowly and with difficulty, should respond similarly to the chilled fruit.

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20 40 s080 coo /00 40o /60 / H0oFIG. 8. Respiration of bananas as determined by various workers.

479



PLANT PHYSIOLOGY

In fig. 8 are shown the determinations of various workers who have in-vestigated the respiration of bananas. The curve of the average of severalcheck lots is also repeated for comparison. From a study of these curves,it will be seen that these workers used bananas which were already welladvanced in the ripening processes. This point was first established byE. F. HOPKINS.2 As. a matter of fact, LANGWORTHY (18) states that thefruit was "more mature than usual," also, that it hung in the laboratoryover night; and GORE (9) says that the "bananas were on the point ofturning yellow." OLNEY (25) makes mention of the relative maturity ofthe fruit used but even his "least mature" was far from green, as can beseen from the curve. Furthermore, his work being done in Chicago wouldmake it even more difficult to obtain fruit which had not encounteredfavorable conditions for the ripening processes. By a comparison of thesecurves and also those in fig. 7, it seems safe to conclude, that in the case ofthe previously reported work, and in the experiments herein presented inwhich the controls ripened rapidly that the fruit was already well alongin the ripening processes when the experiments were begun, and thatfurthermore, this was due to the fruit having previously been exposed tofavorable ripening conditions or to substances such as ethylene, acetylene,or other volatile substances which would stimulate the ripening processesas indicated by a high initial respiratory rate and an immediate rapid riseof the same.

The work of HIBBARD (15) and WOLFE3 with ethylene would seem tofall in line with these observations and conclusions. The fruit which HIB-BARD found to require 232 hours to color was probably chilled, and that"which had been exposed to low temperature for too long a period" wasprobably more than just chilled, or had also received other deleterioustreatment. Low humidity sometimes has injurious effects which are simi-lar to chilling, but the response of the fruit so exposed would not be thesame. All the work herein reported was with very high humidity.

Though no previous work has been reported as to acetylene acting simi-larly to ethylene in the ripening of bananas, there is evidence in the litera-ture which indicates that this is in line with its behavior. It has beenreported as causing-nutations, (16, 17, 24, 29); changes in the chemicalcomposition of germinating seeds and tubers, (10); decomposition ofchlorophyll, (8, 11); production of intumescences, (35); breaking of restperiods, (23, 36, 37, 38); and inhibition of growth, (17, 39).

2 HOPKINS, E. F. Respiration and ripening of bananas. Unpublished report to theUnited Fruit Co. 1-46. 1927.

3 WOLFE, H. S. The effect of ethylene on the ripening of bananas. Paper pre-sented before the Amer. Soc. Plant Physiologists, Cleveland meetings, 1930.

480




Though the action of acetylene, ethylene, and propylene seems to besomewhat different from that of other substances, notably as regards thewide range of effective concentrations, there is still insufficient evidence toconnect this behavior with the unsaturated condition of the molecule.Many other substances have been shown to be capable of hastening theripening of fruits (34), and forcing plants (5, 6, 7, 33, 37). The actionof these grases on horticultural material has been more completely presentedin a paper by IIARTsIIORN.4

SummaryThe experiments here reported show that the "carbide treatment" has-

tens the ripening processes of thoroughly green bananas as shown by therates of softening, respiration, starch hydrolysis, flavor and color changes.That these effects are due to acetylene rather than ammonia or some otherimpurity in the gas seems fairly well established by the experiments inwhich the gas was purified. It has not been shown that no ethylene waspresent in the acetylene, but it seems very unlikely in view of the condi-tions under which the gas was produced and purified, and the low- coneen-tration of acetylene used in some experiments. There appeared to be nosharp limits to the concentrations of acetylene giving these results.

Though the difference in the respiratory rate may be considerably in-creased at a given time by the treatment, the maximum respiratory rateduring the ripening may not be greatly changed by the treatment exceptin the case of severely chilled fruit. The effect appears to be mainly inthe abbreviation of the period of low activity normally occurring at thebeginning of the ripening processes or which may be considerably extendedby unfavorable conditions such as chilling.

The condition of the fruit at the beginning of the experiment is ofprime importance as to the results obtained. It is suggested, that the highinitial respiratory rates determined by previous workers were due to thefact that the fruit was well advanced in the ripening processes, at the be-ginning of the experiments, due either to exposure to favorable ripeningconditions, or to stimulation by ethylene, acetylene or other volatile sub-stances of similar action.

The results with acetylene are in agreement with those obtained withethylene, and also with its previously determined effects on horticulturalmaterial.

WASHINGTON, D. C.

4 HARTSHORN, ROBERT H. The effect of acetylene, ethylene and prophylene on horti-cultural material. Cornell University Thesis, 1-38. 1929.

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PLANT PHYSIOLOGY

LITERATURE CITED1. BACHER, T. 0. The effect of ammonia in the air on growth of the

plant. Cornell University thesis, 1-35. 1928.2. CROCKER, WM. and KNIGHT, L. I. Effect of illuminating gas and

ethylene upon flowering carnations. Bot. Gaz. 46: 259-276.1908.

3. DENNY, F. E. Hastening the coloration of lemons. Jour. Agr. Res.27: 757-769. 1924.

4. . Effect of ethylene upon respiration of lemons. Bot.Gaz. 77: 322-329. 1924.

5. . Second report on the use of chemicals for hasteningthe sprouting of dormant potato tubers. Amer. Jour. Bot. 13:386-396. 1926.

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EFFECTS OF ACETYLENE - Plant Physiology · SOME EFFECTS OF ACETYLENE ON THE RIPENING PROCESSESOFBANANAS' R. HARTSHORN (WITHEIGHTFIGURES) Introduction In recent years there has been