A simple apparatus for measuring oxygen uptake and carbon dioxide output

Summary The respiration apparatus described is essentially a large-scale Warburg apparatus, with numerous details in the design which are considered essential for reliable results. The oxygen uptake is not derived from a manometric reading however, but from replacement of the oxygen by a measured amount of water. By this means frequent calibration of the apparatus for differing quantities of material is avoided. The use of the apparatus for measuring respiration in both air and gas mixtures is described.

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Zusammenfassung Der hier beschriebene Respirations-Apparat ist im wesentlichen ein volumin?ser Warburg-Apparat mit zahlreichen Einzelheiten in der Konstruktion, die für das Erreichen von verl?sslichen Resultaten wesentlich sind. Die Sauerstoffaulnahme erhalten wir nicht durch die Ablesung am Manometer, sondern durch die Verdr?ngung des Sauerstoffs durch eine gemessene Wassermenge. Hierdurch ist das h?ufige Kalibrieren des Apparates für verschiedene Mengen des Materials vermieden. Die Verwendung des Apparates zur Messung der Atmung sowohl in Luft-als in Gasmischungen ist beschrieben.

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Résumé L'appareil respiratoire décrit ici est en somme la reproduction en grand de l'appareil de Warburg, avec de nombreux détails de construction jugés indispensables pour obtenir des résultats súrs. Cependant, la consommation d'oxygène n'est pas connue par une lecture manométrique mais par le remplacement de l'oxygène par une quantité d'eau mesurée. De cette facon, les fréquents jaugeages de l'appareil pour différentes quantités de substance sont évités. L'emploi de l'appareil est décrit pour les mesures de la respiration, aussi bien dans l'air que dans de mélanges gaseux.

     

The effect of oxygen concentration on the sugar content of potato tubers stored at low temperature

Summary Mature potato tubers of the varietyMajestic were stored, at 1°C, in concentrations of oxygen from 0 to 100% for a period of one month. The contents of sucrose and reducing sugar and the CO₂ production of the tubers were measured. Concentrations of oxygen of 3% and below delayed the accumulation of sugars in the tubers compared with that in air. In N₂ the accumulation was prevented, while the CO₂ production continued at a low rate. At oxygen concentrations above 3% the sucrose level rose to a maximum after three weeks and then slowly fell, while the reducing sugar content increased throughout. Under these conditions carbon dioxide production increased rapidly to a peak at about 7 days and then slowly fell to near the initial level.     

The production of growth-suppressing volatile substances by stored potato tubers

Summary The sprout-suppressing constituent(s) of the volatiles may be removed by a solution of silver sulphate in 96% H₂SO₄ or by aqueous solutions of mercuric acetate or chloride. but not by 96% H₂SO₄ alone, suggesting that they may be olefinic, ethereal and/or sulphur-containing. Ethylene may be produced in very small quantities, insufficient to be an active olefinic constituent.     

Amylolytic activity in stored potato tubers. 2. The effect of low-temperature storage on the activities of α-and β-amylase and α-glucosidase in potato tubers

Summary Tubers of the potato cultivars Record, Wilja, Pentland Dell and Brodick (formerly clone 137371) were sampled before and after storage at either 4°C or 10°C. Reducing sugar content stayed constant during storage at 10°C in all four cultivars but rose greatly during the first 6–12 weeks of storage at 4°C in Record, Wilja and Pentland Dell but not in Brodick. Amylolytic activity was determined after 5 weeks storage using blockedp-nitrophenyl maltoheptaoside as substrate for α-amylase,p-nitrophenyl maltopentaoside as substrate for β-amylase, andp-nitrophenylglucopyranoside as substrate for α-glucosidase. The values obtained from tubers stored at 4°C were higher than those from tubers stored at 10°C, the differences being much less in Brodick than in the other three cultivars.     

Effects of relative humidity,oxygen, and carbon dioxide on initiation and early development of stolons and tubers

Russet Burbank potatoes were grown in the greenhouse to explore the effects of soil O₂, CO₂, and relative humidity on tuberization. The composition of the gas phase surrounding the below ground stem and stolons was controlled at various levels. Prolonged levels of CO₂ greater than 5% produced large lenticels and, in combination with high relative humidity suppressed the number of stolons. Oxygen levels of 5% or less in prolonged contact with the stolons and underground portion of the stem were favorable to stem decay by pathogens but did not affect lenticel size. Isolating the stolons in a low relative humidity environment delayed tuber set, but increased the number of tubers per plant. This effect of low humidity suggests that the onset of tuberization involves at least two inductive factors, one of which is not translocated among stolons.     

Using the Tabor Atomizer System to maintain weight and firmness in stored potato tubers

A new fogger — the Tabor Atomizer System — features unique atomizers, based on compressed air and water. The droplets produced have a very small mass (less than 10m,) and behave like a dry cloud, producing 96%–98% relative humidity (RH) without depositing free water on the tubers. After 6 months of storage at 10 C, with 96%–98% RH applied with the Tabor Atomizer System (room A), 92%–94% applied with a spin-disk humidifier (room B), and 82%–86% with no added humidity (room C), the weight losses for stored potatoes were 2%, 7%, and 12%, respectively. The firmness of the tubers expressed as newtons (N) required to penetrate the tubers before storage and after 6 months in room A, B, or C was 76, 74, 68, or 63 N, respectively.     

A quick method of obtaining samples for the estimation of carbon dioxide,oxygen and volatiles in the potato tuber

A 5 min evacuation technique utilizing the purging effect of steam, and the vacuum produced by its condensation, was used to collect and compare O₂, CO₂, ethanol and ethylene from potato tubers surface treated with substances inhibiting normal respiratory exchange.     

A portable monitor for the rapid assessment of processing quality of stored potato tubers

The present study assessed a commercially available, enzymatically based blood glucose monitor for the rapid determination of processing quality of tuber samples taken directly from storage. This monitor is based on reflectance photometry of a disposable test strip for a chromogen produced during the oxidation of glucose. The influence of storage conditions, harvest location, cultivar, reconditioning effects and the monitoring environment were examined for their effects on glucose levels and chip color. Glucose concentrations were determined by blood glucose monitor, high performance liquid chromatography (HPLC) or YSI biochemical analyzer. Crude tuber extracts did not adversely affect the determination of glucose by the blood glucose monitor and there was no evidence of any interaction between glucose concentration and extract in terms of test strip color development. The test strips demonstrated stable color retention for over an hour although values remained slightly higher after the initial potato extract test. Reaction of test strips to glucose was sensitive to initial temperature of the tuber extract with greatest accuracy exhibited in the 15–22 C range. Chip color was inversely correlated with tuber glucose content regardless of detection method, cultivar, growing site or storage temperature. The highly portable glucose monitor provided a rapid, accurate and quantitative profile of chip processing quality.     

The sugar content and sprout growth of tubers of potato cultivar Record,grown in different localities,when stored at 10, 2 and 20°C

Summary Mature tubers, from 13 centres between 211 and 837 km N of 50 N, were stored at 10°C in 1966 and 1967, and always showed an initial rise in reducing sugar. In 1966 this obliterated the effect of latitude upon sugar content. At harvest, 20 crops had a sugar content acceptable for processing. A few weeks later only 2 were acceptable. The increased sugar decreased on transfer to 20°C, the samples behaving similarly, and thus showing no effect of latitude of growing centre after ‘conditioning’. Such treatment, being slow, would be commercially practicable only if the desired changes were small. The start of sprout growth at 10°C, and accompanying start of carbohydrate mobilization, showed no effect of latitude. Nor did the amount of sugar accumulated at 2 C, despite a suggestion of an effect on initial rate of sweetening. The initial rate of subsequent de-sweetening at 20°C was positively correlated with the amount of accumulated sugar.

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Zusammenfassung Reife Knollen der Sorte Record, die in den Jahren 1966 und 1967 an 13 Zentren zwischen 211 und 837 km N des 50 N angebaut wurden. wurden bei 10°C gelagert. In jedem Fall erfolgte in den ersten paar Wochen der Lagerung ein Ansteigen des Gehaltes an reduzierenden Zukkern (Tabellen 1 und 2), 1966 überdeckte dieser Anstieg den Einfluss der Distanz n?rdlich des Anbauzentrums auf den Zuckergehalt, der w?hrend des Wachstums und bei der Reife augenscheinlich war. Bei der Ernte wiesen 20 Best?nde einen für die Verarbeitung annehmbaren Zuckergehalt auf, aber nach dem Ansteigen zu Beginn der Lagerung waren nur noch zwei annehmbar (Tabelle 3). Sp?ter besserte sich dies etwas. Aber nur in einem Fall sank der Zuckergehalt auf den Stand zur Zeit der Ernte (Tabellen 1 und 2). Eine Anzahl anderer Sorten zeigten ein ?hnliches Verhalten (Tabelle 4). Nach verl?ngerter Lagerung (Mai–Juni) steig der Zuckergehalt, besonders der Saccharose, was für das altersbedingte Süsswerden charakteristisch ist (Tabellen 1, 2 und 4). Die dafür verantwortliche Mobilisierung des Kohlehydrats beginnt sehr bald nach Beginn des Keimwachstums, aber sie verursacht das Süsswerden nur dann, wenn die Mobilisierung die Ansprüche des Wachstums übersteigt. Bei handelsüblicher Lagerung mit Keimverhinderung k?nnte das Süsswerden gef?hrlicher sein als hier verzeichnet. Der Beginn des Keimwachstums unterschied sich zwischen den Sorten (Tabelle 7), aber er zeigte keinen Einfluss des Anbauzentrums, obwohl sich die Wachstumsrate unterschied, indem sie oft, aber nicht ausschliesslich, bei den Mustern aus dem fernen Norden kleiner war (Tab. 5, 6). Muster der Ernte 1966, die am Anfang der Lagerperiode von 10°C auf 20°C gebracht wurden, wiesen eine Abnahme im Gehalt an reduzierenden Zuckern auf, sie war aber nicht mehr von Bedeutung, wenn die Knollen sp?ter, nach Beginn des altersbedingten Süsswerdens, umgelagert wurden (Tabelle 8). Die Abnahme war in jedem Fall ?hnlich. Es war kein Einfluss des Breitengrades des Anbauzentrums festzustellen. Ein Einzelversuch über Zuckeranh?ufung bei 2°C zeigte keinen Einfluss der Lage des Anbauzentrums auf die am Schluss angeh?ufte Menge, obwohlauch diese betr?chtlich schwankte (Tabelle 9). Es gab einen deutlich positiven Einfluss des Ortes auf die Zuckerakkumulationsrate, der jedoch einer Best?tigung bedarf. Die nachfolgende Rekonditionierung durch Lagerung bei 20°C war im Mai gleich wirksam wie im M?rz. Die Rate war mit der bei der Umlagerung auf 20°C vorhandenen Zuckermenge positiv korreliert (Tabelle 10).

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Résumé Des tubercules m?rs de la variété Record, cultivée dans 13 centres situés entre 211 et 837 km au nord du 50e degré de latitude nord, ont été conservés à 10°C. Dans chaque cas, il y a eu une augmentation de la tencur en sucres réducteurs durant les premières semaines de stockage (tableaux 1 et 2). En 1966, cette élévation a masqué l'effect de la localisation des centres de culture sur les sucres réducteurs; celle-ci étant apparente pendant les périodes de végétation et de stockage. A la récolte, 20 lots ont eu une teneur en sucres acceptable pour la transformation mais, après leur élévation pendent la période de stockage, 2 lots seulement convenaient (tableau 3). On observait une amélioration par la suite mais, dans un cas seulement, la concentration revenait au taux initial (tableaux 1 et 2). Un certain nombre de variétés se comportaient de fa?on identique (tableau 4). Après une conservation prolongée (mai–juin), on notait une augmentation de la teneur en sucres, notamment en saccharose, caractéristique du ‘sucrage’ d? à la sénescence (tableaux 1, 2 et 4). La mobilisation des hydrates de carbone responsables de ce phénomène s'effectuait aussit?t après le démarrage de la germination et ne causait le ‘sucrage’ que lorsqu'elle excédait la quantité nécessaire à la croissance des germes. Dans le stockage pour la commercialisation avec utilisation d'inhibiteurs de germination, le ‘sucrage’ pourrait être plus important que celui mentionné ici. Le démarrage de la germination variait selon les variétés (tableau 7) mais la localisation des différents centres n'avait pas d'effet sur lui: toutefois, les taux de croissance étaient différents, étant souvent mais pas exclusivement moindre, pour les échantillons provenant des centres de culture les plus éloignés (tableaux 5 et 6). Les échantillons récoltés en 1966 et stockés rapidement à 10 et 2°C ont montré une diminution de leur teneur en sucres réducteurs, qu'il n'était plus possible d'apprécier lorsque les tubercules avaient été stockés plus tardivement, au moment où le ‘sucrage’ d? à la sénescence était déclenché (tableau 8). La diminution de la teneur en sucres était identique dans tous les cas, démontrant l'absence d'effet de la latitude des centres de cultures. Un seul essai sur l'accumulation des sucres dans les tubercules conservés à 20°C a montré cette absence d'effet de la latitude des centres de culture sur la concentration finale en sucres: cependant, des variations considérables ont été observées (tableau 9). Il y avait un effet positif apparent de la latitude qui demandait une confirmation. Par la suite, la diminution du taux de sucres par un temps de passage des lots à 20°C a été observée de la même manière en mai qu'en mars. Le taux était en corrélation positive avec la quantité de sucres présente au moment du transfer à 20°C (tableau 10).

     

A novel method for investigating the uptake and distribution of radiolabelled imazethapyr in potato tubers

Summary The use of imazethapyr as a sprout suppressant in potatoes has been investigated. Novel radionuclide techniques were developed to establish the patterns of uptake and movement of imazethapyr in potatoes. Protocols for tissue analysis were established to homogenise potato tuber tissue samples, enabling radiolabel recovery by liquid scintillation counting to approach 100%. The movement of imazethapyr was also examined in the presence of an acidic formulation of thiabendazole which caused increased uptake. The movement of imazethapyr within the tuber was also influenced by pH and ion trapping.     

Temperature,cyanide, and oxygen effects on the respiration,chip color,sugars, and organic acids of stored tubers

The possibility that sugar accumulation of potatoes stored at low temperatures may be linked to activation of cyanide-resistant respiration (CRR) was investigated. After a lag period of several days, continuous HCN treatment stimulated CO₂ production of tubers stored in 20% O₂. At 1°C in 20% O₂, HCN treatment increased respiration over that effected by low temperature treatment. After several weeks of treatment, cyanide-stimulated CO₂ production was greater at 1°C than at 10°C. Sucrose and malate levels of HCN treated tubers were sometimes higher than those of the 10°C control tubers, but they were always lower than those of the 1°C control tubers. This indicated that CRR alone could not account for the sugar increases at 1°C. Storage in 2% O₂ blocked the increase in CO₂ production and changes in constituents associated with HCN treatments in 20% O₂. HCN treatment had no significant effect on chip color. The level of CRR was measured in freshly cut slices from Monona, Norchip, and Kennebec tubers previously stored at 10°, 5°, or 1°C for several months. Slices from tubers previously stored at 1°C had increased CRR, but there was no difference in CRR between the 5°C and 10°C treatments. Sugars accumulated at 5°C, again indicating that sugar accumulation in potatoes stored at low temperatures was at least partially independent of the activation of CRR.     

Post-wounding changes in the oxygen consumption by slices from tubers of several potato cultivars

Summary Potato (Solanum tuberosum L.) cultivars differed markedly in their susceptibility to autolysis during the post-wounding period. Slices from cultivars susceptible to autolysis showed higher respiration rates than those sampled from resistant cultivars. The higher oxygen consumption of these cultivars was inhibited by imidazole. Application of the respiration inhibitors, KCN and SHAM, to the slices showed that the capacity of the alternative electron transport pathway was relatively high during the post-wounding period in fresh slices of cultivars resistant to autolysis. The capacity of that pathway was near zero in the susceptible tissues. Aging promoted the development of KCN-resistant respiration in both types of cultivars.     

The nature of a cytokinin in potato tubers

Summary Using ethyl acetate extraction in a liquid-liquid extractor three cell division inducing compounds, that coelute with authentic cytokinins, were extracted from sprouting potato tubers. The major peak of activity coeluted and cochromatographed with zeatin riboside. In the low resolution mass spectrometer the active substance yieldedm/e peaks characteristic of N-6- substituted adenines.     

Blackspot of Russet Burbank potatoes and the carbon dioxide content of soil and tubers

These studies were designed to elucidate the influence of CO₂ on blackspot susceptibility of Russet Burbank potatoes. The influence of tuber CO₂ environment on blackspot was tested. Tubers from 1–4 and 6–8 inches deep in the soil were scored for blackspot and moisture samples were taken from their vicinity. Blackspot was worse in shallow tubers and in tubers from drier soil. Plowing under corn stover, covering the soil with plastic, and excessive irrigation failed to cause blackspot susceptible tubers. Diffusing CO₂ into the soil atmosphere under plastic sheets slightly increased the intensity of spot discoloration but the discoloration was atypical blackspot. Effects on blackspot by changing tuber gases was tested. Tubers whose gases had been evacuated and replaced by O₂, N₂, and CO₂ had lower blackspot scores than untreated tubers. Increasing the time tubers were soaked in water after gaseous evacuation reduced blackspot. Hydration consistently decreased tuber blackspot. In chemical studies, tubers were tested for blackspot and analyzed for CO₂ content. The relationship between tissue CO₂ and blackspot appeared to be inverse. Tuber CO₂ content was not influenced by time of day. Tuber blackspot scores immediately, 1, 3, and 7 hours after digging were the same, but tissue CO₂ content increased linearly with time after harvest.     

A mechanism for low temperature induced sugar accumulation in stored potato tubers: The potential role of the alternative pathway and invertase

The accumulation of reducing sugars in stored potato tubers is of significant commercial importance because of its effect on processing quality. The process by which the accumulation of sugars occurs involves the interaction of many metabolic pathways and is yet to be fully described. Low temperature conditions result in an accumulation of ATP in potato tissue. Published evidence suggests that low temperature activation of the alternative pathway (cyanide resistant respiration) leads to decreased ATP levels and simultaneous increases in sucrose concentrations. This sucrose becomes the substrate for vacuolar acid invertase resulting in the accumulation of reducing sugars. Inhibition of the alternative pathway results in decreased sugar accumulation thereby minimizing the sucrose available to the acid invertase and the subsequent reducing sugar accumulation. Control of the alternative pathway on its own, or in combination with acid invertase activity, may provide insight into the phenomenon of low temperature sweetening in stored potato tubers.     

Modeling the effects of light, carbon dioxide, and temperature on the growth of potato

This study examined the effects of light, temperature and carbon dioxide on the growth of potato (Solanum tuberosum L.) in a controlled environment in order to ascertain the best growing conditions for potato in life support systems in space. 'Norland' and 'Russet Burbank' were grown in 6-L pots of peat-vermiculite for 56 d in growth chambers at the University of Wisconsin Biotron. Environmental factor levels included continuous light (24-h photoperiod) at 250, 400, and 550 micromoles m-2 s-1 PPF; constant temperature at 16, 20, and 24 degrees C; and CO2 at approximately 400, 1000, and 1600 microliters L-1. Separate effects analysis and ridge analysis provided a means to examine the effects of individual environmental factors and to determine combinations of factors that are expected to give the best increases in yields over the central design point. The response surface of Norland indicated that tuber yields were highest with moderately low temperature (18.7 degrees C), low CO2 (400 microliters L-1) and high light (550 micromoles m-2 s-1 PPF). These conditions also favored shorter stem growth. Russet Burbank tuber yields were highest at moderately low temperature (17.5 degrees C), high CO2 (1600 microliters L-1) and medium analyses will be used to project the most efficient conditions for growth of potatoes in closed ecological life support systems (CELSS) in space colonies.     

Changes in sugar content and invertase activity in tubers of some Indian potato varieties stored at low temperature

Summary Significant differences were found in sugar content and invertase activity of tubers of 8 Indian cultivars stored at 3–5°C. Freshly harvested tubers of all the cultivars had low amounts of sugars, which increased during storage, and little or no basal invertase activity but both basal and total invertase activities in all the cultivars increased during storage. There were significant correlations between the reducing sugar content and basal and total invertase activities. Publication no. 116, Central Potato Research Institute, Shimla.     

Interaction of ethylene,oxygen and carbon dioxide in the control of fruit ripening

Ethylene production during the climacteric in many fruits, in vegetative tissue treated with IAA, and in flowers which have been emasculated, pollinated or treated with IAA applied to their stigma, increases rapidly and then returns to a low rate. In root sections exposed to IAA this timing apparently is due to the fact that the rate of ethylene production reflects the internal IAA content; the latter increases initially after auxin is applied but rapidly decreases again due to induction or activation of the enzyme systems conjugating and destroying IAA. A similar mechanism may be involved in the induction of ethylene production in fruits.In vivo ethylene is derived from methionine, possibly after the amino acid is activated to form S-adenosyl methionine, by decarboxylation of C₁, transfer of C₂ possibly as a folic acid derivative, formation of ethylene from C₃–C₄, and transfer of the S-methyl to a suitable receptor molecule.Analogue studies indicate that ethylene attaches (K_A=6×10^–10M) to a metal containing receptor by one end through a non-covalent bond. This attachment is competitively inhibited by CO₂ (K_I=4.9×10^–4M) thus explaining the ability of this gas to antagonize most biological responses to ethylene, including fruit ripening. CO₂ does not inhibit ethylene production, but may influence fruit ripening and induce certain physiological disorders by binding to metal containing enzymes such as catalase. Ethylene production is inhibited at low O₂ concentrations; the receptor has an O₂ affinity closely similar to that of cytochrome oxidase. In addition O₂ is required for ethylene action, and the kinetics best describing the situation are those in which O₂ binds to the receptor (K_S=4×10^–5M) or indirectly oxidizes it before ethylene can attach. This effect of low pO₂ is not dependent upon a respiratory inhibition for it occurs at O₂ concentrations which are not low enough to inhibit respiration and cannot be duplicated by respiratory poisons. Thus low concentrations of O₂ retard fruit ripening both by inhibiting ethylene production and action.The rate of gas exchange and hence the internal concentration of ethylene within a fruit depends upon the diffusion coefficient of ethylene in air. As this is a function of atmospheric pressure, storing fruits at a subatmospheric pressure reduces their ethylene content. In addition this condition automatically decreases the O₂ partial pressure thus greatly extending the storage life of preclimacteric fruits.

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Zusammenfassung In vegetativen Geweben, die mit IAA (-Indolessigsäure) behandelt wurden, in sterilisierten oder befruchteten Blüten, oder in solchen, bei denen die Narbe mit IAA behandelt wurde sowie in vielen Früchten während des Klimakteriums, steigt die Äthylenbildung zunächst rasch an und sinkt dann auf eine niedrige Produktionsrate ab. In Wurzelschnitten, die mit IAA behandelt wurden, spiegelt der zeitliche Verlauf der Äthylenbildung die Zusammenhänge zwischen innerer IAA-Konzentration und Äthylen-Produktionsrate wider. Nach Auxin-Applikation steigt der IAA-Gehalt zunächst an, sinkt dann jedoch wiederum rasch ab. Dieses Verhalten lässt sich mit der Induktion und Aktivierung des Enzymsystems erklären, das die IAA bindet und abbaut. Ein ähnlicher Mechanismus mag bei der Induktion der Äthylenbildung eine Rolle spielen.In vivo wird das Äthylen aus dem Methionin gebildet. Dabei erfolgt wahrscheinlich zunächst eine Überführung in das S-Adenosyl-Methionin, wonach das C₁ decarboxyliert wird. Anschliessend wird das C₂ — vermutlich als Folsäurederivat — abgespalten und das Äthylen aus dem C₃ und C₄, nach Übertragung der Methylmercapto-Gruppe auf ein geeignetes Rezeptor-Molekül, gebildet.Analoge Untersuchungen zeigen, dass sich das Äthylen mit einem Ende an einen metallhaltigen Rezeptor in Form einer nicht kovalenten Bindung anlagert (K_A=6×10^–10M). Diese Bindung wird durch das CO₂ kompetitiv gehemmt (K_I=4,9×10^–4M). Hierdurch ist die Fähigkeit des CO₂ erklärt, in sehr vielen biologischen Prozessen, einschliesslich der Fruchtreife, zum Äthylen antagonistisch zu wirken. Das CO₂ verhindert nicht die Äthylenbildung, aber es kann die Fruchtreife beeinflussen und bestimmte physiologische Störungen durch Bindung metallhaltiger Enzyme — beispielsweise der Katalase — hervorrufen. Bei niedrigen O₂-Konzentrationen ist die Äthylenbildung gehemmt. Der Rezeptor hat eine weitgehend ähnliche O₂-Affinität wie die Cytochrom-Oxidase. Darüberhinaus ist O₂ für die Wirksamkeit des Äthylen erforderlich. Die reaktionskinetischen Vorstellungen, die die Situation am besten beschreiben, sind folgende: O₂ verbindet sich mit dem Rezeptor (K_S=4×10^–5M) oder oxidiert ihn indirekt, bevor das Äthylen ihn erreichen kann. Der Effekt, den ein geringer O₂-Partialdruck hervorruft, besteht nicht in einer Atemhemmung, denn er spielt sich auf einem O₂-Konzentrationsniveau ab, das für Atemhemmungen nicht niedrig genug ist. Ausserdem kann der Effekt durch Atemgifte nicht verdoppelt (vergrössert) werden. Eine geringe O₂-Konzentration kann daher die Fruchtreife auf zwei Weisen verzögern: Senkung der Bildungsrate und Verringerung der Wirksamkeit des Äthylens.Der Umfang des Gas-Austausches und somit die Äthylen-Konzentration innerhalb einer Frucht hängen vom Diffusions-Koeffizienten von Äthylen in Luft ab. Da dieser eine Funktion des atmosphärischen Druckes ist, senkt Aufbewahrung von Früchten bei Unterdruck ihren Äthylen-Gehalt. Diese Bedingung vermindert darüberhinaus den O₂-Partialdruck, wodurch die Lagerfähigkeit von Früchten im Vorklimakterium stark erweitert wird.

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Resume La production d'éthylène pendant la phase climactérique de nombreux fruits, dans les tissus végétatifs traités à l'acide indole acétique (AIA), et dans les fleurs qui ont été émasculées, pollinisées ou traitées à l'AIA au niveau du pistil, augmente rapidement, puis s'abaisse jusqu'à une vitesse faible. Dans des sections de racines traitées à l'AIA, ce processus est apparemment dû au fait que la vitesse de production de l'éthylène reflète le contenu interne en AIA. Ce contenu augmente initialement après que l'auxine est appliquée, mais décroît rapidement à nouveau à cause de l'induction ou l'activation du système enzymatique de synthèse et de dégradation de l'AIA. Un mécanisme similaire peut être impliqué dans la production de l'éthylène dans les fruits.In vivo l'éthylène provient de la méthionine, probablement après l'activation de l'acide aminé pour former la S-adénosyl-méthionine, par décarboxylation du C1, transfer possible de C₂ comme dérivé de l'acide folique, formation d'éthylène à partir du C₃–C₄, et transfer du S-méthyl à une molécule réceptrice adéquate.Des études analogues indiquent que l'éthylène se lie (K_A=6×10^–10M) à une extrémité d'un récepteur contenant un métal, par un lien non convalent. Cette liaison est compétitivement inhibée par CO₂ (K_I=4,9×10^–4M) ce qui explique la propriété de ce gaz en tant qu'antagoniste dans la plupart des réponses biologiques de l'éthylène, y compris dans la maturation des fruits. Le CO₂ n'inhibe pas la production même d'éthylène, mais peut influencer la maturation du fruit et induire certaines perturbations physiologiques en se liant à des enzymes contenant un métal comme la catalase. La production d'éthylène est inhibée par de faibles concentrations en oxygène; le récepteur a une affinité pour l'oxygène très proche de celle de la cytochrome oxydase. En outre, l'oxygène est nécessaire à l'action de l'éthylène, et les cinétiques décrivant le mieux la situation sont celles dans lesquelles l'oxygène se lie au récepteur (K_S=4×10^–5M) ou oxyde celui-ci indirectement, avant que l'éthylène ne puisse s'y lier. Cet effet des pressions basses en oxygène ne dépend pas de l'inhibition respiratoire puisqu'il se produit à des concentrations d'oxygène qui ne sont pas assez faibles pour inhiber la respiration, et puisqu'il ne peut pas être remplacé par les effets des poisons respiratoires. Donc de faibles concentrations en oxygène retardent la maturation du fruit, à la fois en inhibant la production et l'action de l'éthylène.La vitesse des échanges gazeux, et par conséquent la concentration interne d'éthylène à l'intérieur d'un fruit, dépend du coefficient de diffusion de l'éthylène dans l'air. Comme celui-ci est une fonction de la pression atmosphérique, la conservation des fruits à des pressions inférieures à celles de l'atmosphère réduit contenu en éthylène. De plus, cette condition fait automatiquement diminuer la pression partielle en oxygène, et augmente ainsi considérablement la durée de vie en conservation des fruits préclimactériques.