Inhibited Ethylene Production Research Articles

Is the effect of wounding on leaf senescence due to ethylene?

Wounding delays the loss of chlorophyll (Chl) that normally occurs when oat ( Avena sativa L.) leaf segments are held in the dark. There was a continued increase in ethylene production during the senescence of the control segments; in contrast, ethylene production by the wounded segments, although it increased by a factor of 2–3 times, reached its peak in 48 h and then dropped sharply to below the basal level. Added 1-aminocyclopropane-1-carboxylic acid (ACC) caused a very large increase in ethylene production in both control and wounded segments, but it increased the rate of Chl loss, though only marginally. Aminoethoxyvinylglycine (AVG) inhibited ethylene production by both control and wounded segments and this did decrease the Chl loss, but only in the control segments. In the wounded segments, AVG antagonized the Chl-retaining action of the wound. Since wounding delayed the loss of Chl and yet caused a moderate increase in ethylene production, we conclude that the ethylene production by senescing oat leaves is not the main controlling influence in the wounding effect. The data also throw doubt on the causal participation of ethylene in normal Chl loss by these leaves in darkness.

Ethylene Production in Seedlings of Chenopodium rubrum, as Influenced by Seedlings Age, Light, and CO2 Concentration1)

Summary Ethylene formation in intact seedlings of a short-day plant Chenopodium rubrum was followed in the course of the first 26 d of growth. The highest values of ethylene evolution were found in the youngest (2 1/2-d-old) plants. Ethylene evolution then decreased up to the 4th d as expressed both on dry weight and on one plant basis. Later, ethylene evolution expressed on dry weight basis decreased till the 26th d, while that expressed on one plant basis increased from the 5th d onward, the rate of increase gradually leveling off. The peaks of flowering coincided with periods of low ethylene production, as expressed on dry weight. Light inhibited ethylene production in C. rubrum seedlings. A higher CO, level did not cancel such inhibition. A lower CO 2 level decreased ethylene production in darkness. ACC markedly increased ethylene evolution and this ACC-induced ethylene production is inhibited by light more strongly than that in the absence of ACC. The relationship between the levels of auxin and ethylene and the capacity for flowering is discussed.

Opposing effects of daminozide and ethylene on the induction of flesh softening in apple fruits

SummaryApple trees were sprayed in late July with daminozide in four seasons to suppress ethylene production and softening of harvested fruit stored in 2% O2, <1% CO2 at 3.5°C. In two out of three years daminozide applied at 0.43 g l−1 was ineffective whereas ethylene production, softening and the rise of soluble pectin were inhibited by 0.85 or 1.7 g l−1. In the third season all the spray treatments were ineffective. In bulk storage experiments a combination of daminozide treatment and ethylene removal by potassium permanganate-impregnated vermiculite led to the retention of fruit firmness in two years out of three; untreated fruit and fruit which received only one of the treatments softened to a similar extent. The dual treatment also inhibited the solubilization of pectin and the synthesis of butyl and hexyl acetates during ripening after storage. Whereas daminozide-treated fruit had higher chlorophyll levels than untreated fruit, ethylene removal had no effect on chlorophyll loss. A taste panel distinguished the low ethylene-daminozide treated fruit as firmer and less mealy than other treatments. However, this fruit had a higher incidence of storage disorders.

Effects of Salicylate on Virus‐Infected Tobacco Plants

AbstractSalicylate watered onto the soil of tobacco plants in pots reduced the antigen accumulation and local lesion growth of tobacco necrosis virus mechanically inoculated on the leaves. It also retarded the growth of the necrotic centres of lesions and, in parallel, inhibited ethylene production from infected leaves. However, the therapeutic index of salicylate was very small and the chemical had to be applied in advance of, or at the same time as virus inoculation to give good levels of resistance. The number of lesions and their rate of appearance were not affected by salicylate. In addition, it did not induce resistance against multiplication, systemic spread or symptom severity in tobacco plants inoculated with a necrotic strain of potato virus Y.These findings suggest that salicylate is not likely to prove useful as polyvalent chemotherapeutic agent.

Role of Ethylene in the Senescence of Isolated Hibiscus Petals

Senescence of petals isolated from flowers of Hibiscus rosa-sinensis L. (cv Pink Versicolor) was associated with increased ethylene production. Exposure to ethylene (10 microliters per liter) accelerated the onset of senescence, as indicated by petal in-rolling, and stimulated ethylene production. Senescence was also hastened by basal application of 1-aminocyclopropane-1-carboxylic acid (ACC). Aminooxyacetic acid, an inhibitor of ethylene biosynthesis, effectively inhibited ethylene production by petals and delayed petal in-rolling. In marked contrast to these results with mature petals, immature petals isolated from flowers the day before flower opening did not respond to ethylene in terms of an increase in ethylene production or petal in-rolling. Furthermore, treatment with silver thiosulfate the day before flower opening effectively prevented petal senescence, while silver thiosulfate treatment on the morning of flower opening was ineffective. Application of ACC to both immature and mature petals greatly stimulated ethylene production indicating the presence of an active ethylene-forming enzyme in both tissues. Immature petals contained less free ACC than mature, presenescent petals and appeared to possess a more active system for converting ACC into its conjugated form. Thus, while the nature of the lack of responsiveness of immature petals to ethylene is unknown, ethylene production in hibiscus petals appears to be regulated by the control over ACC availability.

5′-Methylthioadenosine Nucleosidase and 5-Methylthioribose Kinase Activities and Ethylene Production during Tomato Fruit Development and Ripening

5'-Methylthioadenosine (MTA) nucleosidase and 5-methylthioribose (MTR) kinase activities were measured in crude extracts of tomato fruits (Lycopersicon esculentum Mill cv Rutgers) during fruit development and ripening. The highest activity of MTA nucleosidase (1.2 nanomoles per milligram protein per minute) was observed in small green fruits. The activity decreased during ripening; at the overripe stage only 6.5% of the peak activity remained. MTR kinase activity was low at the small green stage and increased thereafter until it reached peak activity at the breaker stage (0.7 nanomoles per milligram protein per minute) followed by a sharp decline at the later stages of fruit ripening. 1-Amino-cyclopropane-1-carboxylic acid (ACC) levels peaked at the red stage, while ethylene reached its highest level at the light-red stage. Several analogs of MTA and MTR were tested as both enzyme and ethylene inhibitors. Of the MTA analogs examined for their ability to inhibit MTA nucleosidase, 5'-chloroformycin reduced enzyme activity 89%, whereas 5'-chloroadenosine, 5'-isobutylthioadenosine, 5'-isopropylthioadenosine, and 5'-ethylthioadenosine inhibited the reaction with MTA by about 40%. 5'-Chloroformycin and 5'-chloroadenosine inhibited ethylene production over a period of 24 hours by about 64 and 42%, respectively. Other analogs of MTA were not effective inhibitors of ethylene production, whereas aminoethoxyvinylglycine showed a 34% inhibition over the same period of time. Of the MTR analogs tested, 5-isobutylthioribose was the most effective inhibitor of both MTR-kinase (41%) and ethylene production (35%).

In vivo production of ethylene from 2-keto-4- methylthiobutyrate in mice

The use of 2-keto-4-methylthiobutyric acid (KMB), the alpha-keto analog of methionine, was studied as a potential means of detecting free radical generation in vivo. KMB-dependent ethylene production (presumably from free radical interception), and ethane production from in vivo lipid peroxidation, were monitored simultaneously by measuring the rate of exhalation of these hydrocarbons by mice. Injection of KMB (1 g/kg) into mice resulted in an 8-fold increase in ethylene production above endogenous levels seen in saline-injected controls (1.47 ± 0.35 vs 0.17 ± 0.02 nmoles/100 g/hr respectively). Administration of CCl4 (3.0 g/kg) to initiate hepatic lipid peroxidation, 20 min prior to KMB injection, augmented the production of ethylene (2.37 ± 0.10 nmoles/100 g/hr). Lipid per-oxidation following injection of CCl4 was monitored via the increased exhalation of ethane. Pretreating the mice with vitamin E (100 mg/kg daily for 3 days), an inhibitor of lipid peroxidation, did not result in a significant change in ethylene production from KMB by itself or after prior injection of CCl 4. However, vitamin E did suppress ethane production initiated by CCl 4. Similar results were obtained with mouse liver slices studied in vitro. Metyrapone (150 mg/kg), an inhibitor of hepatic mixed function oxidase activity, also suppressed significantly the CCl 4-stimulated production of ethane, but not the CCl 4-stimulated production of ethylene from KMB. It appears that ethylene production from KMB does not derive from free radicals generated during in vivo lipid peroxidation since suppression of lipid peroxidation by vitamin E or metyrapone did not suppress ethylene production.

Brassinosteroid-Induced Epinasty in Tomato Plants

The effects of root treatments of brassinosteroid (BR) on the growth and development of hydroponically grown tomato plants (Lycopersicon esculentum Mill cv Heinz 1350) were evaluated. There was a dramatic increase in petiole bending when the plants were treated with 0.5 to 1.0 micromolar BR. The leaf angle of the treated plants was almost three times that of untreated controls. BR-induced epinasty appeared to be due to stimulation of ethylene production. Excised petioles from BR-treated plants produced more than twice as much ethylene as did untreated controls. As ethylene production increased, the degree of petiole bending also increased, and inhibition of ethylene production by AOA or CoCl(2) also inhibited epinasty. BR-treated plants had increased levels of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) in the leaf tissue. ACC appeared to accumulate primarily in the petioles with the greatest amount of ACC accumulating in the youngest petioles. Time course evaluations revealed that BR treatment stimulated ACC production. As ACC accumulated, ethylene increased, resulting in epinasty. Little or no ACC was found in the xylem sap, indicating that there was a signal transported from the roots which stimulated ACC synthesis in the leaf tissue.

Relationship between the activity of the ethylene-forming enzyme and the level of intracellular 2,4-dichlorophenoxyacetic acid in pear cell culturesin vitro

Ethylene production by auxin-dependent pear cells culturedin vitro falls rapidly when they are deprived of 2,4-D. This phenomenon is associated with a decrease in ACC production. Readdition of 2,4-D causes a resumption of ACC production and ethylene synthesis. Ethylene-forming enzyme (EFE) activity, although never limiting, decreases sharply during 2,4-D depletion and rises again upon addition of 2,4-D. This increase in the EFE activity is not a rapid response to 2,4-D, since it requires several hours. Changes in EFE activity follow the same pattern as changes in 2,4-D concentration; the decrease in EFE activity is also concomitant with a decrease in the ability of 2,4-dinitrophenol to inhibit ethylene production. The possible role of auxins in the modulation of EFE activity is discussed.

Reversal of Nematode-induced Growth Retardation in Tomato Plants by Inhibition of Ethylene Action

Abstract Tomato plants (Lycopersicon esculentum) infected with root-knot nematodes, Meloidogyne javanica, contain 2.2 to 2.6-times higher levels of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) in the roots and leaves compared with uninfected plants. The nematode-induced increase in the ACC coincides with increased ethylene production in the infected plants. Foliar spray with aminoethoxyvivyl-glycine (AVG), which inhibits ethylene production or with silver thiosulfate (STS) which inhibited ethylene action, partially or completely eliminated the pathogenic symptoms displayed by a nematode-infected plant, indicating that the ethylene induced by the nematode infection plays a major role in the pathogenic symptoms infliced by the nematode. Foliar spray with 3 mM STS 4 to 8 days after the nematode inoculation was found to be the most effective treatment for reversing the nematode infection symptoms.

The effects of aminoethyoxyvinylglycine on maturity and post‐harvest changes in Cox's Orange Pippin apples

AbstractPre‐harvest spraying of orchard trees with aminoethoxyvinylglycine (AVG) suppressed ethylene production in apples at picking and during barn storage. Fruit firmness was not affected at harvest, but the fruit softened more slowly and remained greener longer after picking. Changes in volatile aroma components were noted and autocatalytic stimulation of ethylene was not possible. AVG did not reduce the acceptability of the fruit at harvest time: subsequently an increased preference for fruits from unsprayed trees was shown by a sensory assessment panel.

Promotion and inhibition by plant growth regulators of aerenchyma formation in seedling roots of Zea mays

The influence of naphthylacetic acid, abscisic acid, gibberellic acid and kinetin on the formation of aerenchyma in seedling roots of Zea mays L. cv. Capella has been studied in relation to reported changes of their concentration in poorly aerated roots, which readily form aerenchyma, and to the effects of these hormones on the production of ethylene, a major factor promoting aerenchyma formation. Because the absence of nitrate accelerates aerenchyma formation in aerated roots, their influence on these roots was compared. The growth regulators were added to roots growing in non‐aerated and aerated nutrient solutions, and aerenchyma formation and the production and endogenous concentration of ethylene were measured. Naphthylacetic acid prevented aerenchyma formation in both aerated roots without nitrate and in non‐aerated roots although it enhanced the ethylene concentration of the roots. Abscisic acid also prevented aerenchyma formation, but without affecting the ethylene concentration. Gibberellic acid promoted aerenchyma formation in aerated roots only, but ethylene production in both aerated and non‐aerated roots. Kinetin promoted aerenchyma formation in both aerated and non‐aerated roots. It stimulated ethylene production in aerated roots, but slightly inhibited it in non‐aerated roots. Co2+ and Ag+, which suppress ethylene production and action, respectively, reduced the promoting effects of gibberellic acid, but not those of kinetin. It is concluded that the effects of the plant growth regulators on aerenchyma formation in maize roots were, with a possible exception for gibberellic acid, not the result of altered ethylene concentrations in the roots. Their influence on aerenchyma formation is discussed in relation to their reported actions on cell membranes.

Differential effects of silver salts in apple tissue

Effects of silver nitrate (AgNO 3) and silver thiosulphate (STS) on ethylene production from apple cortex cylinders and on viability of isolated apple protoplasts have been studied. The response to both silver salts in these two systems is similar: AgNO 3 inhibits ethylene production and is toxic to protoplasts; STS is ineffective on ethylene production and does not harm protoplasts.

Ethylene Biosynthesis and Xylogenesis inLactucaPith Explants CulturedIn Vitroin the Presence of Auxin and Cytokinin: The Effect of Ethylene Precursors and Inhibitors

The possible involvement of ethylene in the induction of xylem differentiation was studied in lettuce (Lactuca sativa L. cv. Romaine) pith parenchyma expiants. The addition of the ethylene precursors L-methionine (0-25 //M), S-adenosylmethionine (25 /rM) and 1-aminocyclopropane-l-carboxylic acid (0-01 /?M), or the ethylene-releasing agent 2-chloroethylphosphonic acid (1-0 //M), to a standard IAA-kinetin-containing medium enhanced xylogenesis compared to control expiants cultured in the absence of these compounds. In the presence of the ethylene inhibitors aminoethoxyvinylglycine, Co(N03)2 and AgN03, xylogenesis was inhibited. Inhibition of xylogenesis by aminoethoxy vinylglycine (75 /?M), Co(N03)2 (50 //M) and AgN03 (6-0 //M) was reversed by exogenous 1-aminocyclopropane-l-carboxylic acid (0-01 //M), 2-chloroethylphosphonic acid (5-0 ,uM) and L-methionine (0-25 //M), respectively. Ethylene production by expiants cultured on media containing L-methionine or 1-aminocyclopropane-l-carboxylic acid was greater than the biosynthesis of ethylene by expiants cultured in the absence of these compounds. The incorporation of 2-chloroethyl phosphonic acid into the culture medium resulted in higher rates of ethylene production compared to expiants cultured on the IAA-kinetin medium. The presence of either aminoethoxyvinylglycine or Co(N03)2 inhibited ethylene production by expiants cultured on the IAA-kinetin medium. The data support the hypothesis that ethylene plays a positive role in the initiation of xylem differentiation.

Does Light Inhibit Ethylene Production in Leaves?

The effect of light on the rate of ethylene production was monitored using two different techniques-leaf segments incubated in closed flasks versus intact plants in a flow-through open system. Three different plants were used, viz sunflower (Helianthus annuus), tomato (Lycopersicon esculentum), and soybean (Glycine max). Experiments were conducted both in the presence and absence of 1-aminocyclopropane-1-carboxylic acid (ACC).The results obtained indicate that, in all three species studied, light strongly inhibits ethylene production when cut leaf segments are incubated in the presence of ACC in closed flasks. When ethylene measurements are made with ACC-sprayed intact plants using a continuous flow system, the effect of light on ethylene production is only marginal. In leaf segments of sunflower and soybean incubated only in distilled H(2)O in closed flasks, light promotes ethylene production. In tomato, there is no difference between the rate of ethylene production between light and darkness under such conditions. When measurements are made with intact plants in a continuous flow system, the rate of ethylene production is almost identical in light and darkness, in the three plants studied.It is concluded that the effect of light on cut leaf segments incubated in the presence of ACC in closed flasks can be attributed to the techniques used for these measurements. Light has little effect on ethylene production by intact plants in an open system.

Effect of low oxygen and high carbon dioxide on the levels of ethylene and 1-aminocyclopropane-1-carboxylic acid in ripening apple fruits

The association of the level of ACC and the ethylene concentration in ripening apple fruit (Malus sylvestris Mill, var. Ben Davis) was studied. Preclimacteric apple contained small amounts of ACC and ethylene. With the onset of the climacteric and a concomitant decrease in flesh firmness, the level of ACC and ethylene concentration both increased markedly. During the postclimacteric period, ethylene concentration started to decline, but the level of ACC continued to increase. Ethylene production and loss of flesh firmness of fruits during ripening were greatly suppressed by treatments with low O2 (O2 1–3%, CO2 O%) or high CO2 (CO2 20–30%, O2 15–20%) at the preclimacteric stage. However, after 4 weeks an accumulation of ACC was observed in treated fruits when control fruit was at the postclimacteric stage. Treatment of fruit with either low O2 or high CO2 at the climacteric stage resulted in a decrease of ethylene production. However, the ACC level in fruit treated with low O2 was much higher than both control and high CO2 treated fruit; it appears that low O2 inhibits only the conversion of ACC to ethylene, resulting in an accumulation of ACC. Since CO2 inhibits ethylene production but does not result in an accumulation of ACC, it appears that high CO2 inhibits both the conversion of ACC to ethylene and the formation of ACC.

Phytotoxic effects of cadmium in leaf segments ofAvena sativa L., and the protective role of calcium

It is shown that ethylene production can be stimulated in peeled oat leaf segments in the dark by cadmiun at concentrations below 0.01 mM, and that cadmium-stimulated stress ethylene accelerates senescence processes. Higher cadmium concentrations cause membrane deterioration and inhibit ethylene production and senescence. These effects of cadmium are antagonized by calcium. This indicates a possible protection of plant cell against cadmium toxicity by calcium.

α‐Aminoisabutyric acid, propyl gallate and cobalt ion and the mode of inhibition of ethylene production by cotyledonary segments of cocklebur seeds

Using cotyledonary segments of cocklebur (Xanthium pennsylvanicum Wallr.) seeds, the inhibitory effect of α‐aminoisobutyric acid (AIB) on ethylene production was compared with that of propyl gallate and CoCl2. Of these inhibitors only AIB was effective in causing the accumulation of endogenous free 1‐aminocyclopropane‐l‐carboxylic acid (ACC) in the tissue. The degree of inhibition of ethylene production by AIB decreased markedly with increasing concentrations of pre‐loaded ACC, while the inhibition by propyl gallate and CoCl2 changed little. Kinetic analysis showed that AIB competitively inhibited the conversion of pre‐loaded ACC to ethylene, but propyl gallate and CoCl2 did not. Short‐chain organic acids and analogues of AIB, such as acetic, propionic, butyric and cyclopropanecarboxylic acids, did not inhibit ethylene production by the segments. Thus, additional support for the competitive mode of inhibitory action of AIB on the conversion of free ACC to ethylene was provided.A conjugated hydrolysable ACC was found to be present in abundance in cotyledons of this seed. However, its content in the tissue was hardly affected by treatment with the three inhibitors and by administration of exogenous ACC, suggesting that the conjugated ACC was not directly involved in ethylene production.

Involvement of hydroperoxides and an ACC-derived free radical in the formation of ethylene

Microsomal membranes from etiolated peas, a model system capable of catalysing ethylene formation from 1-aminocyclopropane-1-carboxylic acid (ACC), were used to investigate the involvement of hydroperoxides and free radicals in the terminal step of ethylene biosynthesis. t-Butyl hydroperoxide ( t-BuOOH) and cumene hydroperoxide increased ethylene production by up to 19- and 9-fold respectively when added to the basic reaction mixture consisting of microsomes and ACC in buffer. These enhancement effects were both heat-denaturable, and that of t-BuOOH also proved to be sensitive to catalase. By contrast, hydrogen peroxide inhibited ethylene production. Lipoxygenase and linolenic acid stimulated ethylene production, and removal of endogenous hydroperoxides by the addition of GSH and GSH peroxidase almost completely inhibited the formation of ethylene. Spin trapping studies with 4-( N-methylpyridinium) t-butylnitrone revealed an ACC-dependent free radical species, the production of which could be inhibited by Tiron, a disulphonated catechol that reacts with O 2 − dot . The data collectively suggest that the enzymatic conversion of ACC to ethylene by pea microsomal membranes is hydroperoxide-dependent, and is mediated by O 2 − dot through a free radical intermediate of the substrate.

Effects of Exogenous 1,3-Diaminopropane and Spermidine on Senescence of Oat Leaves

Excision and dark incubation of oat (Avena sativa L., var. Victory) leaves cause a sharp increase in protease activity, which precedes Chl loss. Both these senescence processes are inhibited by exogenously applied 1,3-diaminopropane (Dap), which occurs naturally in leaf segments. The inhibition of protease activity is much greater in vivo than in vitro, suggesting inhibition of protease synthesis as well as protease action by Dap. Chl breakdown in leaves of radish and broccoli, which also senesce rapidly in the dark, is only slightly inhibited by DaP. These differences between cereal and dicotyledonous plants are correlated with the natural occurrence of Dap in cereals. In the light, Dap promotes, rather than retards, the loss of Chl in oat leaves. This resembles previously described effects of other polyamines. Addition of Mg(2+) to the medium does not antagonize this effect. In the dark, the accumulated Dap also inhibits ethylene production and decreases titer of other polyamines. Addition of Ca(2+) to the incubation medium containing Dap competitively reduces the effects of Dap. Thus, Dap, like other polyamines, seems to require an initial attachment to a membrane site shared with Ca(2+) before exerting its antisenescence action.