Emission of ethylene and ethane by leaf tissue exposed to injurious concentrations of sulfur dioxide or bisulfite ion

Leaf tissues injured with SO₂ gas or bisulfite ion in solution emit ethylene and ethane. The amounts of these gases produced by the tissues depend on the degree of exposure to SO₂ or bisulfite. The amount of ethylene produced in response to SO₂ fumigation correlates positively with SO₂ exposure (0 to 5.5 microliters per liter for 16 hours), SO₂ absorbed, and the amount of visible injury sustained by the leaf tissues. Ethane production is correlated positively with the injury resulting from treatment with bisulfite ion. The rate of emission of ethane from leaf discs of cucurbit cultivars as a result of exposure to bisulfite solutions is in agreement with the order and the degree of their resistance to injury by SO₂. Thus, exposure to bisulfite and the subsequent release of ethane can be used to determine the relative resistance of different species and cultivars to SO₂ gas.     

Ethylene, Ethane, Acetaldehyde, and Ethanol Production By Plants under Stress

Red pine (Pinus resinosa Ait.) and paper birch (Betula papyrifera Marsh.) seedlings exposed to sulfur dioxide produced acetaldehyde and ethanol, and exhibited increased production of ethylene and ethane. Gas chromatographic measurement of head space gas from incubation tubes containing leaves or seedlings was a simple method of simultaneously measuring all four compounds. Increased ethylene production had two phases, a moderate increase from the beginning of the stress period and a large increase just prior to appearance of leaf lesions. Ethane production in SO₂-stressed plants did not increase until lesions appeared. Acetaldehyde and ethanol production began within 6 hours at 0.3 microliter per liter SO₂ and 24 hours at 0.1 microliter per liter SO₂ and continued throughout a 6-day fumigation. Production of acetaldehyde and ethanol continued when plants were removed to clean air for up to 2 days. A higher concentration of SO₂ (0.5 microliter per liter) induced acetaldehyde and ethanol production within 2 hours of the start of fumigation of birch and pine seedlings. A number of other stresses, including water deficit, freezing, and ozone exposure induced production of acetaldehyde and ethanol. Production of these compounds was not due to hypoxia, as the O₂ partial pressure in the incubation vessels did not decline. Increasing the O₂ partial pressure to 300 millimeters Hg did not affect production of these compounds. Production of ethylene, acetaldehyde, and ethanol declined when more than 80% of the leaf area became necrotic, while ethane production was linearly related to the percentage of necrosis. A number of woody and herbaceous plant species produced acetaldehyde and ethanol in response to freezing stress, while others did not. Measurement of these four compounds simultaneously in the gas phase may be a valuable method for monitoring plant stress, particularly air pollution stress.     

Early diagnosis of SO2-stress by volatile emissions in some crop plants

Summary Fumigation experiments with SO₂ performed on the seedlings of three plant species viz, tomato (Lycopersicon esculentum), mung bean (Vigna radiata) and maize (Zea mays) resulted in the emission of volatiles. Acetaldehyde and ethanol were produced in the fumigated plants. In addition, there was also an increased production of ethylene and ethane. The production of these volatiles was positively correlated to the SO₂ concentrations of 4.2 and 8.3 mol m^–3 (0.1 and 0.2 ppm). Ethylene was emitted primarily from SO₂-stressed yet healthy leaves, whereas high ethane levels were detected in leaves with visible injury symptoms. However, with the appearance of visible injury symptoms, there was a decline in ethylene, acetaldehyde and ethanol emissions. Synthesis of ethylene and ethane seems to be a result of different metabolic pathways. Ethane evolution and its inhibition by antioxidants indicate SO₂-mediated lipid peroxidation by free radical species formed during sulphite oxidation. Perturbation in the cellular respiratory machinery results in the formation of acetaldehyde and ethanol. Since the rates of emissions of ethane, acetaldehyde and ethanol fromplant species were positively correlated to their relative resistance to SO₂, the production of these gases could be used as a reliable diagnostic tool for biomonitoring air pollution (SO₂) stress.Abbreviations ADH alcohol dehydrogenase - NaHSO₃ sodium metabisulphite - O ₂ ^– superoxide radical - OH hydroxyl radical - pO₂ oxygen partial pressure - SO₂ sulphur dioxide - SO ₃ ^– sulphite radical - SOD superoxide dismutase     

Ethylene and ethane production in response to salinity stress

Abstract Ethylene and ethane production in mung bean hypocotyl sections were evaluated as possible indicators of stress due to contact with four salts that are common in natural sites. Ethylene production decreased with increasing concentrations of applied NaCl and KCl. When CaCl₂ was applied, the ethylene evolution was greater. However, when MgCl₂ was applied, ethylene evolution remained high then decreased and at higher salt concentrations again showed an increase. NaCl (up to 0.1 kmol m^?1) and KCl (up to 0.5 kmol m^?3) caused a concentration-dependent increase in ethane production. The ethane production with CaCl₂ was the lowest among the salts tested and only a minute increase was noticed with the increase of concentration from 0.01 to 1 kmol m^?3. Ethane production showed a distinct maximum at 0.2 kmol m^?3 MgCl₂. The introduction of 0.01 kmol m^?3 CaCl₂, as well as anaerobic conditions obtained by purging vials with N₂, eliminated that high ethane production. Respiratory activity of the mung bean hypocotyl sections in MgCl₂ concentrations from 0 to 0.5 kmol m^?3 was correlated with ethane but not with ethylene production. The ethane/ethylene ratio showed three patterns for the four salts tested.     

Abscission: the role of ethylene modification of auxin transport

The role of ethylene-mediated reduction of auxin transport in natural and ethylene-induced leaf abscission was studied in the cotton (Gossypium hirsutum L., cv. Stoneville 213) cotyledonary leaf system. The threshold level of ethylene required to cause abscission of intact leaves was between 0.08 and 1 μl/l with abscission generally occurring 12 to 24 hours following ethylene fumigation. The threshold level of ethylene required to reduce the auxin transport capacity in the cotyle-donary petiole paralleled that required for stimulation of abscission. In plants where cotyledons are allowed to senesce naturally there is a decline in auxin transport capacity of petioles and increase in ethylene synthesis of cotyledons. The visible senescence process which precedes abscission requires up to 11 days, and increases in ethylene production rates and internal levels were detected well before abscission. Ethylene production rates for entire cotyledons rose to 2.5 mμ1 g⁻¹ hr⁻¹ and internal levels of 0.7 μl/l were observed. These levels appear to be high enough to cause the observed decline in auxin transport capacity. These findings, along with those of others, indicate that ethylene has several roles in abscission control (e.g., transport modification, enzyme induction, enzyme secretion). The data indicate that ethylene modification of auxin transport participates in both natural abscission and abscission hastened by exogenous ethylene.     

Participation of ethylene in common purslane response to dicamba

The responses of common purslane (Portulaca oleracea L.) plants to 2-methoxy-3,6-dichlorobenzoic acid (dicamba) were found to be similar in many respects to ethylene fumigation effects. Dicamba and ethylene increased the permeability of cell membranes in purslane tissues. An increased efflux of electrolytes was observed in the bending region of the stems of dicamba-treated plants. Epinastic leaves after dicamba (10 micrograms) and ethylene (microliter per liter) treatments showed an increased efflux of rubidium. The permeability effects were observable within 1 day after dicamba or ethylene application. Protein metabolism in purslane leaves was not influenced by dicamba until 2 days after treatment, as indicated by reduced nitrate reductase activity. Inhibition of phenylalanine-U-¹⁴C incorporation into protein was observed 3 days after treatment. Ethylene reduced both phenylalanine-U-¹⁴C incorporation into protein and nitrate reductase activity within 1 day. Dicamba caused a rapid increase in ethylene production in purslane plants to levels many times greater than those observed in untreated plants. It was concluded that the dicamba-enhanced production of ethylene is responsible for many of the observed effects of the herbicide.     

Does Water Deficit Stress Promote Ethylene Synthesis by Intact Plants?

The effect of plant water deficit on ethylene production by intact plants was tested in three species, beans (Phaseolus vulgaris L.), cotton (Gossypium hirsutum L.) and miniature rose (Rosa hybrida L., cv Bluesette). Compressed air was passed through glass, plant-containing cuvettes, ethylene collected on chilled columns, and subsequently assayed by gas chromatography. The usual result was that low water potential did not promote ethylene production. When plants were subjected to cessation of irrigation, ethylene production decreased on a per plant or dry weight basis of calculation. No significant promotion of ethylene production above control levels was detected when water deficit-treated bean or cotton plants were rewatered. The one exception to this was for cotton subjected to a range of water deficits, plants subjected to deficits of −1.4 to −1.6 MPa exhibited a transient increase of ethylene production of 40 to 50% above control levels at 24 or 48 hours. Ethylene was collected from intact leaves while plants developed a water deficit stress of −2.9 megapascals after rewatering, and no significant promotion of ethylene production was detected. The shoots of fruited, flowering cotton plants produced less ethylene when subjected to cessation of irrigation. In contrast, the ability of bench drying of detached leaves to increase ethylene production several-fold was verified for both beans and cotton. The data indicate that detached leaves react differently to rapid drying than intact plants react to drying of the soil with regard to ethylene production. This result suggests the need for additional attention to ethylene as a complicating factor in experiments employing excised plant parts and the need to verify the relevance of shock stresses in model systems.     

Foliar Fatty Acids and Sterols of Soybean Field Fumigated with SO(2)

Sixty-day-old soybean plants were exposed in the field to 78.7 parts per one-hundred million of SO₂ in an open-air fumigation system for 20 days. Leaves from the top one-fourth and bottom one-fourth of the plants were analyzed for chlorophyll, free fatty acids, fatty acid esters, polar lipid fatty acids, and sterols. Fumigated plants had a lower chlorophyll, free fatty acid, and polar lipid content, but a higher fatty acid ester content. Of the individual fatty acids, linoleic and linolenic acid increased with SO₂ fumigation while palmitic acid decreased. SO₂ fumigations had only a minor effect on leaf sterols. In general, the lower, more mature leaves showed a greater response to SO₂ exposure.     

A malic Acid permease in isolated vacuoles of a crassulacean Acid metabolism plant

Pine (Pinus silvestris L.) trees subjected to relatively low concentration of SO₂ in the field emit H₂S from the needles, as demonstrated by gas chromatographic analysis after preconcentration on a molecular sieve. H₂S is the only reduced sulfurous compound emitted from SO₂ fumigated leaves. The emission is light and SO₂ concentration dependent. Pine trees in the field and in laboratory experiments continue to emit H₂S several hours after the termination of prolonged SO₂ fumigation. The maximum emission rates observed from pine trees in the field and in laboratory experiments, 14 and 20 nanomoles per milligram chlorophyll per hour respectively, are about the activity expected for the sulfur assimilation pathway in the chloroplasts.     

Determination of some oxidative stress parameters in variegated leaves of Chlorophytum comosum (Thunb) bak

A significantly enhanced production of ethane due to sulphite treatment was observed only in the green fragments of variegated Chlorophytum comosum leaves but no increase in MDA content was found after sulphite treatment either in the green or in the white leaf fragments. The activity of SOD showed a tendency to increase while that of catalase significantly decreased only in the green leaf fragments after SO₂ fumigation. The higher level of oxidative damage in the green tissue could probably result from the Haber-Weiss reaction of generation of HO.     

Can plants exposed to SO2 excrete sulfuric acid through the roots?

Hydroponically grown pea plants (Pisum sativum L., cv. Kleine Rheinländerin) and barley seedlings (Hordeum vulgare L., cv. Gerbel) were fumigated for several days with 1 or 2 μl l^?1 SO₂. Both species accumulated sulfate during fumigation, although the nutrient medium lacked sulfate. In pea, SO₂-dependent sulfate accumulation in different plant parts accounted for 60 percent of the SO₂ sulfur which, as calculated from a determination of boundary and stomatal flux resistances had entered the leaves. Up to 55% of the air-borne sulfate was translocated from pea leaves to roots during the period of fumigation, but no or only little sulfate was excreted into the nutrient solution. In contrast, barley retained sulfate in the leaves, and sulfate translocation from shoot to the root system could not be observed. In both species, protons were excreted by the roots. In fumigated plants, proton loss was higher than in untreated controls in pea, but not in barley. In pea, SO₂-dependent proton loss into the medium accounted for up to 50% of the sulfuric acid formed from SO₂. Proton excretion was strongly dependent on potassium availability in the nutrient medium. Cation uptake by the plants during fumigation was sufficient to compensate for proton loss, suggesting proton/cation exchange at the interface between root and medium. We conclude that by oxidation to sulfuric acid, plants are capable of detoxifying SO₂ taken up by the leaves. Depending on plant species, either both protons and sulfate anions can be exported from the leaves, or the proton load on leaf cells can be relieved by proton/cation exchange at the plasmalemma. Finally, the problem of airborne plant acidification may be solved by proton/cation exchange at the level of roots. The burden of acidification is then shifted from the plant to the nutrient medium. Appreciable amounts of sulfate can be excreted neither by pea nor by barley plants.     

Intact Leaves Exhibit a Climacteric-Like Rise in Ethylene Production before Abscission

The rate of ethylene production by intact, attached leaves of cotton plants (Gossypium hirsutum L.) during aging and senescence was studied using a continuous flow system that allowed air around enclosed leaves to be scrubbed to collect and assay ethylene. Senescence of lower leaves began around 150 d after planting in a controlled environment room. A progressive decline in the ethylene production rate was observed when comparing the 3rd, 6th, and 10th leaves from the base with each other. Ethylene production rates of individual leaves also declined over a 50-d period. However, as leaves began to appear chlorotic, a peak of ethylene production occurred that lasted for about 4 d followed by abscission. This peak involved a 3-fold or greater increase in the rate of ethylene production. The data indicate that intact leaves experience a climacteric-like surge in ethylene production after visible symptoms of senescence appear. This “ethylene climacteric” is apparently the signal that initiates hydrolysis of cell walls in the abscission zone.     

Role of Ethylene in the Geotropic Response of Bermudagrass (Cynodon dactylon L. Pers.) Stolons

We studied the relationship between ethylene and gravity-induced upward bending of bermudagrass (Cynodon dactylon L. Pers.) stolons. Ethylene production begins within 3 hours of the onset of gravistimulation, and increases thereafter until the 15th hour, after which it declines. There is a close positive relationship between ethylene production and upward bending during the first 12 hours of gravistimulation. Incubation of stolons with AgNO₃ did not prevent ethylene evolution but delayed upward bending. In addition, ethylene production was 10-fold greater and peaked earlier in gravistimulated nodes incubated with 1-aminocyclopropane 1-carboxylic acid. The gravitational stimulation could be due to an increase in both 1-aminocyclopropane 1-carboxylic acid synthase and the ethylene forming enzyme. The results suggest that ethylene promotes the activity of indoleacetic acid.     

Extraction of Endogenous Ethylene and Ethane from Leaves of Phaseolus vulgarisL.

A procedure to recover small volumes of gases from plant tissuesby vacuum extraction is described. Changes in the volume ofthe gases and the concentrations of ethylene and ethane recoveredfrom Phaseolus leaves were observed when the evacuation conditionsduring extraction were altered. These changes were differentin the primary leaves and in the second trifoliate leaves. Thus,estimates of internal ethylene and ethane concentrations appearto be influenced both by the morphology of the tissue and theevacuation conditions employed. There was a positive correlationbetween the concentrations of ethylene and ethane in the gaseousextracts. The internal ethylene concentrations in the primary,first trifoliate, and second trifoliate leaves, considered together,were correlated with their respective rates of ethylene emanation.     

Chilling-Induced Ethylene Production in Relation to Chill-Sensitivity in Phaseolus spp.

Guye, M. G, Vigh, L. and Wilson, J. M. 1987. Chilling-inducedethylene production in relation to chill-sensitivity in Phaseolusspp.—J. exp. Bot. 38: 680–690. Ethylene production from the primary leaves of six bean (Phaseolusspp.) cultivars known to differ in chill-sensitivity, was monitoredat 23 ?C following chilling of whole plants at 5 ?C for 24 h.The more chill-tolerant cultivars produced greater amounts ofchilling-induced ethylene than the chill-sensitive cultivars.The onset of maximum ethylene production rates and the followingdecline in rates was more rapid in chill-tolerant cultivars.This pattern of ethylene production was also similar when chill-tolerancewas chemically enhanced by choline treatment. The low levelsof ethylene production in chill-sensitive genotypes was alsoreflected by their poor ability to convert the exogenously appliedethylene precursor, 1-aminocyclopropane-l-carboxylic acid (ACC),to ethylene. Moderate levels of leaf water deficit induced by chilling chill-tolerantcultivars and choline treated plants appeared to stimulate chilling-inducedethylene production. High levels of leaf wilt, shown by morechill-sensitive cultivars, reduced this stimulatory effect.Ethylene production was slightly greater when warming was carriedout in the light rather than in the dark. Key words: Ethylene, ACC, choline, chill-sensitivity, Phaseolus     

Ecology of SO2 resistance

Summary 10 broadleafed trees and shrubs native to the mediterranean climactic zone in California were surveyed for their photosynthetic and stomatal responses to SO₂. These species ranged from drought deciduous to evergreen and had diverse responses to SO₂. These results suggest an approach for predicting SO₂ resistances of plants.We found that conductance values of plants in SO₂-free air can be used to estimate the quantity of SO₂ which plants absorb. These estimates are based on conductance values for plants in non-limiting environmental conditions. SO₂ absorption quantities are then used to predict relative photosynthesis following the fumigation. Thus, relative photosynthesis of plants following fumigation can be predicted on the basis of conductance in SO₂-free air. This approach to predicting SO₂ resistances of plants includes analysis of their stomatal responses to fumigation, their characteristics of SO₂ adsorption and absorption, and their change in photosynthesis resulting from SO₂ stress.     

Ethylene Production and Leaflet Abscission of Three Peanut Genotypes Infected with Cercospora arachidicola Hori

Ethylene can induce abscission of leaves and other plant organs. Increased ethylene production by plant tissues can occur after invasion by microorganisms. The fungus Cercospora arachidicola Hori, attacks peanut leaflets and causes defoliation. Our objective was to determine if ethylene was involved in this defoliation. Leaves of three peanut, Arachis sp., genotypes were inoculated with C. arachidicola. Two genotypes, `Tamnut 74' and PI 109839, produced ethylene and were defoliated. The third genotype, PI 276233, a wild species, did not produce ethylene above control levels and was not defoliated. Increase in ethylene production by Tamnut 74 and PI 109839 coincided with appearance of disease symptoms. Tamnut 74 produced the most ethylene, but PI 109839 was equally defoliated. Thus, less overall ethylene production did not necessarily indicate a more resistant genotype in this system unless ethylene production remained at control levels, as it did for PI 276233. Ethylene sufficient to initiate abscission could have been produced by the seventh day after inoculation when it was similar for both Tamnut 74 and PI 109839, but 3 to 4 times control amounts. This occurred before the rapid increase in ethylene production and before disease symptoms were visible. Silver ion, a potent inhibitor of ethylene action, was sprayed at three concentrations on intact Tamnut 74 plants. All rates reduced abscission and 150 mg/liter Ag(I) decreased abscission to below 10%. The data indicate that ethylene produced by peanut leaves in response to C. arachidicola infection initiates abscission and that ethylene action can be blocked by Ag(I) in such a host-pathogen interaction.     

Ethylene production in rice bronzing leaves induced by ferrous iron

Bronzing, a nutritional disorder of rice plants which is widely distributed in tropical lowlands, was induced by dipping the cut end of rice leaves into FeSO₄ solution (pH 3.5). Ethylene production; the activities of peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase; and the effects of Co²⁺, aminoethoxyvinylglycine, Ag⁺, cycloheximide, and 1-aminocyclopropane-1-carboxylate, were investigated in the course of bronzing development. It was found that ethylene production could be stimulated up to about 20 times that of the control by Fe²⁺, and a peak could be reached at about 24 h after incubation. The Fe²⁺-treated leaves also had 10-fold higher peroxidase activity than the control, whereas in vitro enzyme activity was inhibited by Fe²⁺. Cycloheximide retarded in vivo stimulation of peroxidase, indicating that in vivo stimulation resulted from inducing de novo synthesis of the enzyme. No changes in the activities of phenylalanine ammonia-lyase and polyphenol oxidase were observed. The results, obtained from the incubation of leaves with Co²⁺, aminoethoxyvinylglycine, Ag⁺, cycloheximide, or 1-aminocyclopropane-1-carboxylate, showed that ethylene production was the effect of Fe²⁺ stress and that it was not involved in the process of bronzing development, which is probably an acclimation process to enable plants to cope with stress. The accelerated peroxidase activity may be associated with bronzing development.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - EFE ethylene forming enzyme - PAL phenylalanine ammonia-lyase - POD peroxidase - PPO polyphenol oxidase - SE standard error     

Ethylene-Induced Chlorosis in the Pathogenesis of Bipolaris sorokiniana Leaf Spot of Poa pratensis

Endogenous ethylene of Poa pratensis leaves infected by Bipolaris sorokiniana was evaluated as a factor in leaf chlorosis during pathogenesis. Detectable increases in endogenous ethylene of leaves of intact plants under normal ambient pressure occurred 12 hours after inoculation and was maximum at 48 hours; from 48 to 96 hours the ethylene progressively decreased. Necrotic lesions surrounded by chlorotic halos occurred on infected leaves between 24 and 48 hours. Midvein chlorosis interconnecting individual lesions and complete chlorosis of all tissues not directly affected by the lesions occurred between 72 and 96 hours, after maximum production of ethylene at 48 hours. The chlorophyll loss in infected leaves by 96 hours was 44% compared with controls.

Subjecting inoculated leaves of intact plants to a controlled atmospheric-environmental system with an atmospheric pressure of 233 millibars and O₂ and CO₂ partial pressures adjusted to approximately that of normal ambient pressure during infection and disease development prevented most midvein chlorosis and complete chlorosis, but did not prevent necrotic lesion or chlorotic halo development. Under the hypobaric conditions, chlorophyll loss during disease development was reduced to 22% compared with controls at 96 hours. The observations suggest that ethylene may function late in pathogenesis of this host-pathogen interaction and is responsible for much of the chlorophyll loss after its maximum production at 48 hours.

     

The Role in Ozone Phytotoxicity of the Evolution of Ethylene upon Induction of 1-Aminocydopropane-1-carboxylic Acid Synthase by Ozone Fumigation in Tomato Plants

The rate of evolution of ethylene by tomato plants was rapidlyincreased by O₃ fumigation. The time course of the increasein 1-aminocyclopropane-1-carboxylic acid (ACC) synthase activitywas the same as that in the rate of evolution of ethylene, suggestingthat ACC synthase activity might be a rate-limiting step inthe evolution of ethylene that is caused by O₃ fumigation. Therate of the O₃-induced evolution of ethylene was increased bythe application of ACC to tomato plants, suggesting the involvementof ACC oxidase in the O₃-induced evolution of ethylene. Treatmentof plants with tiron inhibited the evolution of ethane, butnot of ethylene. These results indicated that evolution of ethylenein O₃-treated tomato plants might result from enzymatic reactionscatalyzed by both ACC synthase and ACC oxidase, but not fromstimulation by O₃ of the peroxidation of lipids mediated byfree radicals. Pretreatment of leaves with aminoethoxyvinylglycine (AVG), aninhibitor of ACC synthase, significantly inhibited the evolutionof ethylene that was induced by O₃ and concomitantly reducedthe extent of O₃-induced visible damage to leaves. Treatmentwith 2,5-norbonadiene, an inhibitor of the action of ethylene,strongly reduced the extent of visible damage caused by O₃,even though it did not suppress the evloution of ethylene. Theseresults indicate that ethylene acts on certain metabolic processesto cause visible damage. (Received September 7, 1995; Accepted December 18, 1995)