Stimulation by Ethylene of Chlorophyll Biosynthesis in Dark-grown Cucumber Cotyledons

Five-day-old etiolated cucumber (Cucumis sativus L. var. Alpha Green) cotyledons produced more chlorophyll over a 4-hour illumination period after a prolonged exposure (12 to 72 hours) in the dark to ethylene concentrations ranging from 0.1 to 10 μl/l. Intact seedlings and excised cotyledons responded in the same way to this treatment. This effect does not involve a shortening of the lag phase of chlorophyll accumulation. Exposure of cotyledons to ethylene during the illumination period did not produce the same stimulatory effect on chlorophyll synthesis and, under certain conditions, chlorophyll synthesis was slightly inhibited by exposure to ethylene in the light.     

Stimulation by Ethylene of Mitochondrial Development in Wounded Sweet Potato Root Tissue

Ethylene (about 100 µl per liter) markedly stimulatedincreases in respiratory, Cyt c oxidase and succinate dehydrogenaseactivities of the crude mitochondrial fraction as well as mitochondrialmembrane protein during aging of sliced sweet potato root tissue,indicating that it stimulated mitochondrial development in woundedtissue. It had such an effect even when slices were pre-agedin its absence for 1 day and thereafter aged in its presence.The mitochondrial inner membrane from slices aged in ethylene-containingair was denser than that from fresh slices, while the membranefrom slices aged in ethylene-free air was lighter. Chloramphenicolcompletely inhibited the increase in Cyt c oxidase activitywhether slices were aged in the presence or absence of ethylene.Cycloheximide did not inhibit the increase in slices aged inethylene-free air, but did by 50% in those aged in ethylene-containingair. ¹ This work was supported in part by a Grant-in-Aid (No. 411308)for Scientific Research from the Ministry of Education, Scienceand Culture, Japan. (Received April 4, 1981; Accepted July 7, 1981)     

The Stimulation of Ethylene Synthesis in Nicotiana tabacum Leaves by the Phytotoxin Coronatine

Coronatine is a chlorosis-inducing toxin produced by the plant pathogen Pseudomonas syringae pv atropurpurea. This bacterium is the causal agent of chocolate spot disease, in which brown lesions with chlorotic margins develop on the leaves of Lolium multiflorum Lam. Among the many physiological changes to plants caused by coronatine is the stimulation of ethylene production from bean leaves. The ethyl-substituted side chain of coronatine is an analog of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). We have examined the question of whether part or all of the released ethylene comes from the breakdown of coronatine itself. The rate of ethylene release from leaves of Nicotiana tabacum was proportional to the concentration of coronatine applied to the leaf surface. The lowest effective concentration of coronatine, applied to leaves at 15 pmol cm⁻² of leaf area, resulted in the production of 44 pmol of ethylene cm⁻² over a period of 4 h. The maximum rate of ethylene production occurred 28 to 32 h after application of coronatine. The specific activity of ethylene produced by discs cut from coronatine-treated Nicotiana tabacum leaves floating on a solution containing 10 mm [U-¹⁴C]methionine was consistent with its exclusive origin from methionine. ACC accumulated in the coronatine-treated tissue. ACC synthase activity increased in Phaseolus aureus hypocotyls during a 6-h treatment with coronatine. Thus, coronatine induces the synthesis of ethylene from methionine.     

Stimulation by Ethylene of Axis and Hypocotyl Growth in Bean and Cocklebur Seedlings

Effects of ethylene on the elongation of bean (Phaseolus vulgaris) embryonic axes and hypocotyls, and of cocklebur (Xanthium pennsylvanicum) hypocotyls were studied. In the bean axes, exogenous ethylene was promotive in stimulating longitudinal growth during the early germination period, but thereafter it turned inhibitive. This transition of the ethylene action is likely involved in the appearance of newly differentiated tissues in the hypocotyl, which are negatively sensitive to the gas. The ethylene stimulated elongation of the axes was hardly affected by light or by the presence of the cotyledons. In the bean hypocotyl segment unit, elongation was stimulated by ethylene in its limited zone, when the concentration of ethylene and the exposure times to ethylene were adequate (0.3 to 30 μl/l, 6 to 8 h): Elongation in the much younger region near to the elbow was inhibited by ethylene treatment, whereas the treatment of the upper region of the shank with ethylene finally resulted in significantly increased growth as compared to the untreated controls. In the continuing presence of ethylene over 3 days, the elongation of every region was retarded markedly and radial growth was induced in most regions of the shank from just below the elbow. These ethylene responses occurred independently of red light irradiation, but the ethylene promotion of elongation was lost by shortening the segment height, by removing the hook portion from the segment unit, or with its natural disappearance as a result of ageing. Fundamentally, similar effects of ethylene was observed in cocklebur hypocotyls.     

Thoracic and Abdominal Respiration during the Reproduction of Fixed Respiration Volumes under Chemoreceptor Stimulation

Thoracic and abdominal components of the respiratory system during the reproduction without external feedback of fixed respiration volumes 1V_T, 0.5V_T, and 2V_T were studied in 13 young males. It was found that, during the reproduction of such respiration volumes without visual control, the thoracic and abdominal components of errors do not differ significantly. When the chemoreceptor stimulation increases (during the progressing hypoxia and hypercapnia), the accuracy of the reproduction decreases, mostly because of involuntary overestimation of the abdominal components of the respiration volume.     

Stimulation of Ethylene Production by Exogenous Spermidine in Detached Tobacco Leaves in the Light

Exogenous supply of Spd and Spin stimulated ethylone production in detached tobacco leaves kept in the light. Stimulation, that was first detected after 9 but not 6 h of treatment, linearly increased with concentration and was maintained for several h after returning treated leaves to deionized water. Stimulation of ethylene production was prevented by AVG and Co²⁺ and was accompanied by increased activity of ACC synthase and ethylene-forming enzyme. Put, and other diamines, did not give any stimulatory effect. Stimulation was not accompanied by apparent damage of plasmalomina nor was it reversed by Ca⁺ or Put, suggesting that the cationic properties of polyamines are probably not involved. Stimulation might be due to endogenous polyamine accumulation high enough to inhibit the activity of S-adenosylmethionine decarboxylase, so that all S-adenosyhnethionine might be committed to the ethylene pathway. The stimulatory effect of poly a nines acquires particular interest considering that they have so fur been doscribod to inhibit ethylone production in darkened plant tissues. This finding suggests that polyamines may play a regulatory role in plant development by modulating ethylene bio-synthesis under the control of light.     

Involvement of Ethylene in Chromosaponin-Induced Stimulation of Growth in Lettuce Roots

To elucidate the mode of action of chromosaponin I (CSI) instimulating the growth of lettuce roots (Lactuca sativa L. cv.Grand Rapids), the possible involvement of ethylene was examined.Lettuce seedlings evolved ethylene at a rate of 0.7 nl 10 seeds–¹h–¹. The growth of lettuce roots was stimulated by 2-aminoethoxyvinyl-glycine(AVG), an inhibitor of ethylene synthesis, and 2,5-norbornadiene(NBD), an inhibitor of ethylene action, as well as by CSI. Incontrast to ethylene, treatments with CSI, AVG and NBD promotedlongitudinal elongation of cortical cells of roots and inhibitedtheir lateral expansion. Application of CSI slightly reducedethylene production from lettuce, but this reduction was notsufficient to account for the CSI-in-duced stimulation of growth.The maximal promotive effects of AVG and NBD were obtained at3 µM and 150 µl liter–¹, respectively. Thegrowth promotion by CSI disappeared in the presence of the optimumlevels of AVG or NBD; a further addition of ethylene causedthe stimulatory effects of CSI to increase, depending on theconcentration of ethylene. Thus, CSI reduced both the sensitivityof the roots to ethylene and the maximal effects of ethylene.The CSI-induced stimulation of growth was ascribed to the reductionof the response to ethylene in the lettuce roots. (Received December 20, 1996; Accepted March 16, 1997)     

Nitrilotriacetate Stimulation of Anaerobic Fe(III) Respiration by Mobilization of Humic Materials in Soil

An enrichment culture capable of naphthalene mineralization reduced Fe(III) oxides without direct contact in anaerobic soil microcosms when the Fe(III) was placed in dialysis membranes or entrapped within alginate beads. Both techniques demonstrated that a component in soil, possibly humic materials, facilitated Fe(III) reduction when direct contact between cells and Fe(III) was not possible. The addition of the synthetic Fe(III) chelator, nitrilotriacetic acid (NTA), to soil enhanced Fe(III) reduction across the dialysis membrane and alginate beads, with the medium changing from clear to a dark brown color. An NTA-soil extract was more effective in Fe(III) reduction than the extracted soil itself. Characteristics of the NTA extract were consistent with that of humic substances. The results indicate that NTA improved Fe(III) reduction not by Fe(III) solubilization but by extraction of humic substances from soil into the aqueous medium. This is the first study in which stimulation of Fe(III) reduction through the addition of chemical chelators is shown to be due to the extraction of electron-shuttling compounds from the soil and not to solubilization of the Fe(III) and indicates that mobilization of humic materials could be an important component of anaerobic biostimulation.     

Carbohydrates Stimulate Ethylene Production in Tobacco Leaf Discs : II. Sites of Stimulation in the Ethylene Biosynthesis Pathway

Galactose, sucrose, and glucose (50 millimolar) applied to tobacco leaf discs (Nicotiana tabacum L. cv `Xanthi') during a prolonged incubation (5-6 d) markedly stimulated ethylene production which, in turn, could be inhibited by aminoethoxyvinylglycine (2-amino-4-(2′-aminoethoxy)-trans-3-butenoic acid) (AVG) or Co²⁺ ions. These three tested sugars also stimulated the conversion of l-[3,4-¹⁴C]methionine to [¹⁴C]1-amino-cyclopropane-1-carboxylic acid (ACC) and to [¹⁴C]ethylene, thus indicating that the carbohydrates-stimulated ethylene production proceeds from methionine via the ACC pathway. Sucrose concentrations above 25 mm considerably enhanced ACC-dependent ethylene production, and this enhancement was related to the increased respiratory carbon dioxide. However, sucrose by itself could directly promote the step of ACC conversion to ethylene, since low sucrose concentrations (1-25 mm) enhanced ACC-dependent ethylene production also in the presence of 15% CO₂.     

Characterization of the Stimulation of Ethylene Production by Galactose in Tomato (Lycopersicon esculentum Mill.) Fruit

We have characterized the stimulation of ethylene production by galactose in tomatoes (Lycopersicon esculentum Mill.). The effect of concentration was studied by infiltrating 0, 4, 40, 100, 200, 400, or 800 micrograms galactose for each gram of fresh fruit weight into mature green `Rutgers' fruit. Both 400 and 800 micrograms per gram fresh weight consistently stimulated a transient increase in ethylene approximately 25 hours after infiltration; the lower concentrations did not. Carbon dioxide evolution of fruit infiltrated with 400 to 800 micrograms per gram fresh weight was greater than that of lower concentrations. The ripening mutants, rin and nor, also showed the transient increase in ethylene and elevated CO₂ evolution by 400 micrograms per gram fresh weight galactose. 1-Aminocyclopropane-1-carboxylic acid (ACC) content and ACC-synthase activity increased concurrently with ethylene production. However, galactose did not stimulate ACC-synthase activity in vitro. The infiltrated galactose in pericarp tissue was rapidly metabolized, decreasing to endogenous levels within 50 hours. Infiltrated galacturonic acid, dulcitol, and mannose stimulated transient increases in ethylene production similar to that of galactose. The following sugars produced no response: sucrose, fructose, glucose, rhamnose, arabinose, xylose, raffinose, lactose, and sorbitol.     

Effect of Ethylene and Oxygen on the Development of Cyanide-resistant Respiration in Whole Plant Mitochondria

Mitochondria from whole potatoes (Solanum tuberosum) ordinarily fail to oxidize respiratory substrates and to consume molecular O₂ in the presence of cyanide. Mitochondrial preparations obtained from tubers previously held for 24 hours in ethylene (10 microliters per liter) in air are only partially inhibited by cyanide. Application of ethylene in 100% O₂ led to an additional increase in the resistance of the mitochondrial respiration to cyanide. The resistance to cyanide was accompanied by a decrease in the respiratory control but no change in oxidative phosphorylation as shown by the measurement of ATP synthesis.     

Light Stimulation of Ethylene Release from Leaves of Gomphrena globosa L

The effect of light and CO₂ on both the endogenous and 1-aminocyclopropane-1-carboxylic acid (ACC)-dependent ethylene evolution from metabolically active detached leaves and leaf discs of Gomphrena globosa L. is reported. Treatment with varying concentrations of ACC did not appear to inhibit photosynthesis, respiration, or stomatal behavior. In all treatments, more ethylene was released into a closed flask from ACC-treated tissue, but the pattern of ethylene release with respect to light/dark/CO₂ treatments was the same.

Leaf tissue in the light with a source of CO₂ sufficient to maintain photosynthesis always generates 3 to 4 times more ethylene than tissue in the dark. Conversely, the lowest rate of ethylene release occurs when leaf tissue is illuminated and photosynthetic activity depletes the CO₂ to the compensation point. Ethylene release in the dark is also stimulated by CO₂ either added to the flask as bicarbonate or generated by dark respiration. Ethylene release increases dramatically and in parallel with photosynthesis at increasing light intensities in this C₄ plant. Ethylene release appears dependent on CO₂ both in the light and in the dark. Therefore, it is suggested that the important factor regulating the evolution of ethylene gas from leaves of Gomphrena may be CO₂ metabolism rather than light per se.

     

Stimulation of Fruit Ethylene Production by Wounding and by Botrytis cinerea and Geotrichum candidum Infection in Normal and Non-Ripening Tomatoes

Inoculations with both Botrytis cinerea and Geotrichum candidum stimulated ethylene evolution in the pre-climacteric normal tomato fruit and the non-ripening nor mutant which did not show any rise in ethylene when uninfected. In the post-climacteric normal fruits, new peaks in ethylene production were formed. The rise in ethylene evolution in all types of infected fruits has already been detected during the incubation period of the disease. Ethylene peaks were detected earlier and were higher in fruits infected with B. cinerea than with G. candidum, coinciding with the faster rate of growth of the former. Mechanical wounding also stimulated ethylene synthesis by the non-ripening fruits, production being directly proportional to wound dimension. Considerably higher rates of ethylene were recorded for infected fruits than for mechanically-injured fruits in which wound dimensions were similar to those of lesion development. Applying aminoxyacetic acid at the site of inoculation inhibited ethylene production by 55–60 % in the normal fruits and by about 80 % in the nor mutant fruits. A similar pathway of ethylene synthesis was suggested for normally ripening tomato fruit and non-ripening infected tissues.     

Stimulation of Auxin Induced Ethylene Production in Mung Bean Hypocotyl Segments by 5,5' -Dithiobis-2-nitrobenzoic Acid

The non-permeant protein inhibitor 5,5'-dithiobis-2-nitrobenzoicacid (DTNB) was tested for its effects on auxin induced ethyleneproduction. There was a stimulation in the rate of auxin inducedethylene production at all concentrations of DTNB tested (1,2, 5, and 10 mM). The 5 mM DTNB treatment promoted the maximumstimulation of ethylene production with no further enhancementat the 10 mM concentration. After 12 hr ethylene productionplateaued with 0.1 mM indoleacetic acid (IAA) alone and in combinationwith 1 and 2 mM DTNB. Although the DTNB treatments plateauedit was at a higher level than IAA alone. Both the 5 and 10 mMtreatments of DTNB plus IAA did not show this leveling responseeven after 22 hr at which time these treatments were between90 and 100% higher than the control. There was no stimulationof ethylene production by DTNB in the absence of IAA. Segmentstreated with 10^–4 M rß-naphthaleneacetic acid(NAA) produced significantly higher levels of ethylene thanIAA at the same concentration. Stimulation of ethylene productionby DTNB was greatest at lower concentrations of IAA and NAA.The uptake of ¹⁴C-NAA by mung bean segments was 6-fold greaterin the presence of DTNB than in its absence. Ca^SS was requiredin the incubating media for DTNB to be effective. In the presenceof Ca^SS there was a highly significant increase in ethyleneproduction while in its absence there was no significant effect.The stimulation of IAA induced ethylene production appearedto have a pH optima of 4.6, at higher pH values this responsewas not shown. ¹ Approved for publication May 28, 1981 as paper number 6243in the journal series of the Pennyslvania Agricultural ExperimentStation. (Received June 10, 1981; Accepted January 5, 1982)     

Ethylene Production and Respiration of Postharvest Acid Citrus Fruits and Wase Satsuma Mandarin Fruit

Ethylene production and respiratory rate were examined in acid citrus fruits such as yuzu, seedless yuzu and daidai, and wase satsuma mandarin. A large amount of ethylene was produced from four varieties of citrus fruits harvested from May to July but not after September. A rise in ethylene production did not always coincide with a rise in respiratory rate. Excised tissues of fruits contained the ability of ethylene production throughout the developmental stages. The endogenous ethylene level at the ripening stage, reached the maximum when the color changed from green to yellow.     

Effects of Methyl Jasmonate on Anthocyanin Accumulation, Ethylene Production, and CO2 Evolution in Uncooled and Cooled Tulip Bulbs

Effects of methyl jasmonate (JA-Me) on anthocyanin accumulation, ethylene production, and CO₂ evolution in uncooled and cooled tulips (Tulipa gesneriana L. cvs. Apeldoorn and Gudoshnik) were studied. JA-Me stimulated anthocyanin accumulation in stems and leaves from uncooled and cooled bulbs of both cultivars. The highest level of anthocyanin accumulation was observed in leaves from cooled bulbs treated with 200 μL/liter JA-Me. In sprouting bulbs treated with 100 μL/liter and higher concentrations of JA-Me, the ethylene production began to increase at 3 days after treatment, being extremely greater in uncooled bulbs than in cooled ones. JA-Me also stimulated CO₂ evolution in both cultivars, depending on its concentrations. CO₂ evolution in sprouting bulbs was not affected by cooling treatment. These results suggest that anthocyanin accumulation by JA-Me in tulip leaves is not related to ethylene production stimulated by JA-Me. Received October 10, 1997; accepted November 17, 1997