Effect of gibberellic acid on ACC content,EFE activity and ethylene release by floral parts of the senescing carnation flower

The application of gibberellic acid via the stem of intact preclimacteric carnation flowers inhibited the climacteric surge of ethylene evolution by the flowers. Gibberellic acid also inhibited the rate of ethylene production by all individual floral parts during both the early preclimacteric (low basal level of ethylene production) and the later climacteric stages of flower development. The extent of inhibition did however, vary from one floral part to another. The most pronounced inhibition was recorded in the petal bases between the preclimacteric and senescing stages. This suggests that the petal base is an important regulatory site for ethylene production and therefore may be involved in controlling the onset and degree of petal inrolling. In all floral parts endogenous levels of ACC were reduced with GA₃ treatment, being more pronounced in the petal bases. The potential of the flowers to convert applied ACC to ethylene was not deminished by gibberellic acid.Abbreviations GA₃ gibberellic acid - ACC 1-aminocyclopropane-1-carboxylic acid - EFE ethylene forming enzyme     

Regulation of Ethylene Biosynthesis in Avocado Fruit during Ripening

Preclimacteric avocado (Persea americana Mill.) fruits produced very little ethylene and had only a trace amount of l-aminocyclopropane-1-carboxylic acid (ACC) and a very low activity of ACC synthase. In contrast, a significant amount of l-(malonylamino)cyclopropane-1-carboxylic acid (MACC) was detected during the preclimacteric stage. In harvested fruits, both ACC synthase activity and the level of ACC increased markedly during the climacteric rise reaching a peak shortly before the climacteric peak. The level of MACC also increased at the climacteric stage. Cycloheximide and cordycepin inhibited the synthesis of ACC synthase in discs excised from preclimacteric fruits. A low but measurable ethylene forming enzyme (EFE) activity was detected during the preclimacteric stage. During ripening, EFE activity increased only at the beginning of the climacteric rise. ACC synthase and EFE activities and the ACC level declined rapidly after the climacteric peak. Application of ACC to attached or detached fruits resulted in increased ethylene production and ripening of the fruits. Exogenous ethylene stimulated EFE activity in intact fruits prior to the increase in ethylene production. The data suggest that conversion of S-adenosylmethionine to ACC is the major factor limiting ethylene production during the preclimacteric stage. ACC synthase is first synthesized during ripening and this leads to the production of ethylene which in turn induces an additional increase in ACC synthase activity. Only when ethylene reaches a certain level does it induce increased EFE activity.     

Influence of Plant Hormones on Ethylene Production in Apple, Tomato, and Avocado Slices during Maturation and Senescence

Ethylene production by tissue slices from preclimacteric, climacteric, and postclimacteric apples was significantly reduced by isopentenyl adenosine (IPA), and by mixtures of IPA and indoleacetic acid, and of IPA, indoleacetic acid, and gibberellic acid after 4 hours of incubation. Ethylene production by apple (Pyrus malus L.) slices in abscisic acid was increased in preclimacteric tissues, decreased in climacteric peak tissues, and little affected in postclimacteric tissues. Indoleacetic acid suppressed ethylene production in tissues from preclimacteric apples but stimulated ethylene production in late climacteric rise, climacteric, and postclimacteric tissue slices. Gibberellic acid had less influence in suppressing ethylene production in preclimacteric peak tissue, and little influenced the production in late climacteric rise, climacteric peak, and postclimacteric tissues. IPA also suppressed ethylene production in pre- and postclimacteric tissue of tomatoes (Lycopersicon esculentum) and avocados (Persea gratissima). If ethylene production in tissue slices of ripening fruits is an index of aging, then IPA would appear to retard aging in ripening fruit, just as other cytokinins appear to retard aging in senescent leaf tissue.     

The effect of methyl jasmonate on ethylene and l-aminocyclopropane-1-carboxylic acid production in apple fruits

Methyl jasmonate (JA-Me) at concentration of 0.5 % and 1.0 % in lanolin paste applied to the surface of postclimacteric apples cultivars McIntosh, Spartan, and Cortland inhibited ethylene production in slices of cortex with a skin cut to a depth of about 2 mm. The level of 1-aminocyclopropane-l-carboxylic acid (ACC) was decreased in tissues of apples treated with methyl jasmonate. Methyl jasmonate stimulated ethylene production in preclimacteric apples cv. McIntosh.     

活性氧在UV-B诱导的玉米幼苗叶片乙烯产生中的作用

 研究了活性氧在UV-B(280～320 nm)诱导的玉米(Zea mays)幼苗叶片乙烯合成中的作用。结果表明,UV-B促进了玉米幼苗活性氧和乙烯的产生;乙 烯合成抑制剂氨氧乙烯基甘氨酸 (AVG)和氨氧乙酸(AOA)能明显减弱UV-B对玉米幼苗乙烯产生的诱导作用,但对活性氧(ROS)的 产生没有明显影 响;ROS的清除剂不但能抑制UV-B诱导的 ROS的产生,而且还可以抑制UV_B诱导的乙烯的产生,但这种抑制作用可以被外源O₂^.-的供体所逆转。这 说明,乙烯的积累不能作为UV-B胁迫下ROS的诱导的因素,相反,ROS的积累则导致了乙烯的积累;因此,ROS可能参与了UV-B胁迫诱导的乙烯的产生 。质膜NADPH氧化酶的抑制剂二苯碘鎓(DPI)和H₂O₂的特异性清除剂过氧化氢酶（CAT）对UV-B胁迫诱导的乙烯积累 几乎没有影响, 这说明H₂O₂ 可能与UV-B诱导的玉米幼苗叶片乙烯的产生无关, 在UV-B诱导的玉米幼苗叶片乙烯的生物合成过程中O₂^.-起着很重要的作用,相关的O₂^.-不是由 NADPH氧化酶催化产生的。     

Pith Autolysis in Plants: IV. The Activity of Polygalacturonase and Cellulase during Drought Stress Induced Pith Autolysis

The water potential, amount of pith autolysis and activitiesof apoplastic cellulase and polygalacturonase of tomato stemswere measured during 24 h of drought stress (DS) and for 24h following reirrigation. During DS the water potential droppedfrom —5.5 to —10.4 bars and rose to —8.3 barssoon after reirrigation. Drought stress induced considerablepith autolysis, more of which occurred after reirrigation. Pretreatmentwith mechanical perturbation (MP) of the stems or applicationof exogenous ethephon on the buds hardened the tomato plantsagainst DS-induced pith autolysis. Drought stress caused anincrease in apoplastic polygalacturonase and an even greaterincrease in apoplastic cellulase. Reirrigation caused a largetransient increase in the former and a decrease in the latter.The apoplastic reducing sugar content (as galacturonic acid)of the stem rose in parallel with the activity of the enzymes.Both DS and MP caused an increase in ethylene evolution, althoughthe former was significantly greater than the latter. However,when MP preceded DS, the amount of ethylene produced was significantlyless than DS alone induced. Pretreatment with either MP or exogenousethephon inhibited the increase in apoplastic cellulytic enzymes. It is concluded that DS induces ethylene evolution from thetomato stem, causing an increase in the stem apoplastic cellulyticenzymes, which in turn start the autolysis of the pith cellwalls. Pretreatment with MP or ethephon, each of which inducesethylene evolution, hardens the stem so that it does not producemore ethylene during DS, and thus becomes resistant to DS-inducedpith autolysis. ¹Supported by Bi-national Agricultural Research and Developmentgrant I-127, NASA grant NAGW 96 and NSF grant 8003689to MJJ. ²Permanent address: Horticulture Department, Faculty of Agriculture,The Hebrew University Rehovot, Israel ³Permanent address: Vegetable Crops Department, AgriculturalResearch Organization, the Volcani Center Bet Dagan, Israel     

Influence of Abscisic Acid and Ethylene on Assimilate Distribution in Gladiolus grandiflorus

Water deficit in gladioli, even to the slightest degree, haspreviously been found to decrease assimilate mobilizing abilityof the inflorescence, increase that of the corm and delay translocationout of leaves. The possible involvement of abscisic acid (ABA) and ethylene(ethene) in these modifications was studied. External applicationsof ethrel caused modifications of assimilate distribution andgrowth similar to those caused by water stress but no connexionwas found between the water status of the plants and ethyleneproduction. External applications of ABA caused no change inassimilate distribution of well watered plants. A diurnal patternof inflorescence elongation and water potential () in fieldgrown plants was observed. A significant reduction in the rate of inflorescence elongationand without any change in ABA level was demonstrated in plantstransferred from 92 to 70 per cent relative humidity for 4 h.It is proposed that under water deficit the of the inflorescencedecreases and its turgor-dependent growth is slowed down. Consequentlyits mobilizing ability decreases, followed by delayed translocationof assimilates out of the leaves. The of the corm (the competitivesink) remains high, enabling its growth and assimilate attraction.ABA or ethylene do not seem to be directly involved in thisprocess. abscisic acid, ¹⁴C-assimilate distribution, competitive sink, ethylene, Gladiolus grandiflorus, water deficit     

Postharvest Variation in Cellulase, Polygalacturonase, and Pectinmethylesterase in Avocado (Persea americana Mill, cv. Fuerte) Fruits in Relation to Respiration and Ethylene Production

Cellulase, polygalacturonase (PG), pectinmethylesterase (PME), respiration, and ethylene production were determined in single “Fuerte” avocado fruits from the day of harvest through the start of fruit breakdown. PME declined from its maximum value at the time of picking to a low level early in the climacteric. PG activity was not detectable in the preclimacteric stage, increased during the climacteric, and continued to increase during the postclimacteric phase to a level three times greater than when the fruit reached the edible soft stage. Cellulase activity was low in the preclimacteric fruit, started to increase just as respiration increased, and reached a level two times greater than at the edible soft stage. Cellulase activity started to increase 3 days before PG activity could be detected. Increased production of ethylene followed the increase in respiration and cellulase activity by about 1.5 days. These results indicate that a close relation exists between the rapid increase in the cell wall-depolymerizing enzymes and the rise in respiration and ethylene production and refocused attention on the role of the cell wall and the associated plasma membrane in the early events of fruit ripening.     

The site of 1-aminocyclopropane-1-carboxylic acid synthesis in senescing carnation petals

To study the cause of the uneven production of ethylene by upper and basal portions of detached petals of carnation ( Dianthus caryophyllus L. cv. White Sim), the petals were divided and exposed to ethylene (30 μl 1^-1 for 16 h). The treatment induced rapid wilting and autocatalytic ethylene production in the basal portion similar to that induced in entire petals. In contrast to the response in entire petals and the basal portions, the upper portions responded to ethylene by delayed wilting and much lower ethylene production. Aminocyclopropane carboxylic acid (ACC)-synthase activity in the basal portion of the petals was 38 to 400 times that in the upper portion. In untreated detached petal pieces from senescing carnation flowers, ethylene production by the upper portion declined after 6 h while the basal portion was still producing ethylene at a steady rate 18 h later. Application of ACC to the upper portion of senescing petals increased their ethylene production. α-Aminooxyacetic acid (0.5 m M ), reduced the ethylene production of the senescing basal portion more than that of the upper portion. Endogenous ACC content in basal portions of senescing carnation petals was 3 to 4 times higher than in the upper parts. When detached senescing petals were divided immediately after detaching, the endogenous ACC levels in upper portions remained steady or declined during 24 h after division, while in the basal portions the ACC level rose steadily as in the intact petals. There was no change in the conjugated ACC in either portion after 24 h. Benzyladenine (BA) applied as a pretreatment to entire preclimacteric petals greatly reduced the development of ACC-synthase activity of the basal portion, but had little effect on the activity in the upper portion of the petal. In both portions, however, BA effectively reduced the conversion of ACC to ethylene.     

Ethylene Production by the Lichen Ramalina duriaei

The lichen Ramalina duriaei evolved ethylene when in a wettedstate, the rate of ethylene evolution being constant for atleast the first 20 h. Inhibitors of the ACC (I-aminocyclopropane-I-carboxylicacid) pathway did not inhibit ethylene production. Metal ionsstimulated the production, with Fe²⁺ being the most effective.This stimulation was not affected by inhibitors of the ACC pathwaybut was inhibited by free radical scavengers such as propylgallateand quercitin. Endogenous ACC content was similar whether thelichens were producing ethylene at a basal rate or during Fe²⁺-stimulatedethylene formation. Malondialdehyde and aldehyde contents werehigher in the presence of Fe²⁺. The results are discussed interms of known pathways of ethylene production by micro-organisms. ACC, ethylene, metal ions, methionine, 2-oxo-methylthiobutyric acid, Ramalina duriaei (De Not.) Bagl     

Effect of Water Stress on Gas Exchange in Fronds of the Ostrich Fern (Matteuccia struthiopteris (L.) Todaro)

Experiments were conducted in a gas exchange system to examinethe effect of a water stress, induced by –200 kPa polyethyleneglycol (PEG), on carbon dioxide and water vapour flux, fronddiffusive resistance, intercellular carbon dioxide concentration,carbon dioxide residual resistance and frond water potentialin the ostrich fern (Matteuccia struthiopteris (L.) Todaro).Measurements were taken 1 d after the application of PEG. Themeasurements were made on young fronds (8 d old) and maturefronds (20–24 d old) at PPFD's (Photosynthetic PhotonFlux Density) from 0–1400 µmol m^–22 s^–1.Water stress decreased the net photosynthesis rate in maturefronds at PPFD's of 210 µmol m^–2 s^–1 or greaterand increased the net photosynthesis rate below 210 µmolm^–2 s^–1 in young fronds. The increase in net photosynthesisin stressed young fronds was associated with a significant reductionin the dark respiration rate. Water stress and decreasing PPFD'sincreased frond diffusive resistance. Carbon dioxide concentrationin the intercellular spaces decreased with increasing frondage and PPFD's up to 200 µmol m^–2 s^–1. Theresidual resistance to carbon dioxide flux was not significantlyaffected by either frond age or water stress. Frond water potentialwas significantly lower in mature fronds than in young fronds. Key words: Matteuccia struthiopteris, Water relations, Photosynthesis, Dark respiration     

Post-harvest physiology of tetraploid banana fruit: response to storage and ripening

Aspects of the post-harvest physiology relating to storage and ripening of the fruit of tetraploid banana clones resistant to Sigatoka disease, have been compared with fruit of Valery, an important commercial triploid cultivar. Significant differences in susceptibility to low temperature injury, duration of the preclimacteric period, the texture of pulp and peel and ethylene evolution have been found between tetraploid and Valery fruit and also between tetraploid fruit of different clones. Fruit of Valery and one tetraploid clone developed serious chilling injury during storage at 12 °C whereas that of five other tetraploid clones showed only slight damage. The preclimacteric period for fruit of two tetraploid clones was 30–45% less than for Valery fruit at an equivalent stage of physical development. Pulp firmness of preclimacteric tetraploid fruit was 20–30% less than that of Valery fruit and the differences persisted through ripening. The softening response to applied ethylene was up to 15 h earlier in fruit of tetraploid clones than of Valery but respiratory patterns, colour development and starch-to-sugar conversion were similar. Unlike Valery fruit, ripe tetraploid fruit did not develop senescent spotting, and shelf life was terminated by rapid deterioration of peel strength to a state of severe finger drop. Temporal and quantitative differences occurred between fruit of tetraploid clones and Valery in production of ethylene and these may relate to the observed differences in control of softening in both pulp and peel.     

Effects of Free Radical Scavengers on Stress Ethylene in Soybean Leaves Hypersensitively Reacting to Tobacco Necrosis Virus

The hypersensitive reaction of soybean cuttings to tobacco necrosisvirus is characterized by a large stimulation of stress ethyleneinvolving a marked accumulation of free 1-aminocyclopropane-1-carboxylicacid (ACC) and a moderate increase in ethylene-forming enzyme(EFE) activity. The scavengers of hydroxyl radicals (OH^{dot})sodium benzoate, sodium formate, mannitol and dimethylsulphoxide,did not affect stress ethylene biosynthesis. Propyl gallate,an inhibitor of lipoxygenase enzymes, substantially reducedthe release of stress ethylene from hypersensitive leaves. Thisreduction was not attributable to an inhibitory effect on EFEactivity, but to a strong reduction of free ACC accumulationin leaf tissues. The results suggest that OH^{dot} and the lipoxygenasesystem are not involved in stress ethylene produced during thehypersensitive reaction of soybean to this virus. Glycine max Merr, soybean, ethylene, free radicals, hypersensitivity, tobacco necrosis virus     

Ethylene and Ethane Production in 2,4-D Treated and Salt Treated Tobacco Tissue Cultures

Gas chromatography was used to measure ethylene (ethene) andethane production by tobacco (Nicotiana tabacum cv. Wisconsinno. 38) callus tissues grown on media containing inorganic saltsaccording to Murashige and Skoog (1962), sucrose, myo-inositol,thiamine-HCl kinetic according to Linsmaier and Skoog (1965),and either 2,4-dichiorophenoxyacetic acid (2,4-D) in the range0–100 mgl^–1 or 2 mgl^–1 indoi-3-ylacetic acidplus NaCl in the range 0–200 Meq l^–1. Ethylene productionrates were high (> 500 nl h^–1 g^1– fresh weight)initially in all treatments. Subsequently, ethylene productiondeclined in rapidly growing cultures but remained high in moderatelyand severely 2,4-D (> 0·5 mgl^–1) stressed andin severely NaCl (150 Meql^–1) stressed cultures. Highinitial rates of ethane production (> 200 nl h^–1 g^–1fresh weight) were obtained under conditions of severe stresscaused by 2,4-D or NaCl but not in control or moderately inhibitedcultures. With further incubation ethane production declinedin the severely stressed cultures. It is concluded that ethyleneproduction can be used as an index of moderate 2,4-D stressand severe NaCl stress by virtue of the high persisting ratesof ethylene production in stressed cultures. Ethane productioncan be used as an early index of severe stress caused by either2,4-D or NaCl in vitro. Nicotiana tabacum L., tobacco, ethylene, ethenen, ethane, 2,4-dichlorophenoxyacetic acid, auxin, stress, callus tissue     

Products Released from Enzymically Active Cell Wall Stimulate Ethylene Production and Ripening in Preclimacteric Tomato (Lycopersicon esculentum Mill.) Fruit

Enzymically active cell wall from ripe tomato (Lycopersicon esculentum Mill.) fruit pericarp release uronic acids through the action of wall-bound polygalacturonase. The potential involvement of products of wall hydrolysis in the induction of ethylene synthesis during tomato ripening was investigated by vacuum infiltrating preclimacteric (green) fruit with solutions containing pectin fragments enzymically released from cell wall from ripe fruit. Ripening initiation was accelerated in pectin-infiltrated fruit compared to control (buffer-infiltrated) fruit as measured by initiation of climacteric CO₂ and ethylene production and appearance of red color. The response to infiltration was maximum at a concentration of 25 micrograms pectin per fruit; higher concentrations (up to 125 micrograms per fruit) had no additional effect. When products released from isolated cell wall from ripe pericarp were separated on Bio-Gel P-2 and specific size classes infiltrated into preclimacteric fruit, ripening-promotive activity was found only in the larger (degree of polymerization >8) fragments. Products released from pectin derived from preclimacteric pericarp upon treatment with polygalacturonase from ripe pericarp did not stimulate ripening when infiltrated into preclimacteric fruit.     

盐胁迫条件下提高内源乙烯对拟南芥幼苗生长和根尖活性氧水平的影响

以模式植物拟南芥（Arabidopsis thaliana）为材料,研究了内源乙烯对幼苗耐盐性的影响。研究结果表明,在施加了浓度为100 mmol·L^-1的NaCl胁迫的基质环境中,野生型拟南芥幼苗的根长和根重都显著减小。在施加外源乙烯利后不仅能够缓解盐胁迫对幼苗根伸长生长的抑制作用,而且能够缓解盐胁迫对幼苗根增重生长的抑制作用。施加外源ACC则只能缓解盐胁迫对幼苗根增重生长的抑制作用,而不能缓解盐胁迫对根的伸长生长的抑制。此外,100 mmol·L^-1 NaCl的胁迫条件下,拟南芥幼苗根尖中ROS水平明显升高,而施加了乙烯利和ACC处理下,幼苗根尖ROS的水平在NaCl胁迫下并没有明显的升高,说明内源乙烯可以调控植物体内的ROS维持在正常的水平,使植物体免受氧化损伤,从而提高了幼苗耐盐性。     

Stimulatory and Inhibitory Effects of Sucrose Concentration on Xylogenesis in Lettuce Pith Explants; Possible Mediation by Ethylene Biosynthesis

Numbers of tracheary elements differentiating in lettuce pithexplants rose with increase in concentration of sucrose in themedium up to an optimal concentration of 0·2%, and fellwith further increase in concentration to about one-tenth maximalat 3% sucrose. Although a few tracheary elements formed withoutexogenous sucrose, a very low concentration of sucrose (0·001%)was sufficient to stimulate additional xylogenesis. Pretreatmentof explants with 3% sucrose caused a persisting inhibition ofxylogenesis, especially in tissue that had been near the siteof sucrose application (sandwich technique). The requirementfor adequate, but not inhibitory, concentrations of sucrosefor xylogenesis may underlie the development of xylem alongsidethe sucrose-rich phloem in normal apical morphogenesis. For callus growth the response to sucrose was different: theoptimal concentration was 3%, with a broad plateau from 1 to4% sucrose. Sucrose concentrations of 2 to 3%, used in manytissue culture media, are thus roughly optimal for callus growth,but ten times the optimum for xylogenesis in lettuce pith explants. It is surprising that 0·001% (0·03 mM) sucrose,applied exogenously, can stimulate xylogenesis: endogenous sugarconcentrations are normally higher. Perhaps the stimulationis mediated by ethylene biosynthesis, which is known to be xylogenic.Rates of ethylene production per explant rose with increasingsucrose concentration from about 0·1 nl h^-1 at 0% sucroseto a slightly (significantly) higher level at 0·004%sucrose and to about 0·5 nl h^-1 at 3% sucrose. D -glucoseresembled sucrose in its effects on xylogenesis and ethyleneproduction, but L-glucose yielded no xylogenesis and littlestimulation of ethylene biosynthesis.Copyright 1994, 1999 AcademicPress Lactuca sativa, Coleus blumei, Nicotiana tabacum, lettuce pith explants, tracheary element differentiation, sucrose, glucose, ethylene     

Localization of the Ethylene-synthesizing System in Apple Tissue

Apple (Malus sp.) slices gradually lost the ability to synthesize ethylene when incubated with a mixture of enzymes that digest cell walls. The released protoplasts did not produce ethylene. The release of protoplasts was faster from climacteric fruit slices than from preclimacteric tissue. In protoplast suspension culture, as new cell wall was deposited (as judged by the intensity of fluorescence of regenerating protoplasts stained with Calcofluor White and the incorporation of labeled myo-inositol into their ethanol-insoluble residue), ethylene synthesis was gradually regained. Restored ethylene synthesis reached a maximum after 80 hours in protoplasts from preclimacteric fruit and in 120 hours in those from climacteric tissue. Addition of methionine (1 mm) to the culture medium was essential for appreciable synthesis of ethylene; and this synthesis was inhibited by the aminoethoxy analogue of rhizobitoxine and by propyl gallate, inhibitors of ethylene synthesis in higher plants. We suggest that the ethylene-synthesizing enzyme system is highly structured in the apple cell and is localized in a cell wall-cell membrane complex.     

Promotion by Ethylene of the Capability to Convert 1-Aminocyclopropane-1-carboxylic Acid to Ethylene in Preclimacteric Tomato and Cantaloupe Fruits

The intact fruits of preclimacteric tomato (Lycopersicon esculentum Mill) or cantaloupe (Cucumis melo L.) produced very little ethylene and had low capability of converting 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. When these unripe tomato or cantaloupe fruits were treated with ethylene for 16 hours there was no increase in ACC content or in ethylene production rate, but the tissue's capability to convert ACC to ethylene increased markedly. Such an effect was also observed in fruits of tomato mutants rin and nor, which do not undergo ripening and the climacteric increase in ethylene production during the senescence. The development of this ethylene-forming capability induced by ethylene increased with increasing ethylene concentration (from 0.1 to 100 microliters per liter) and duration (1 to 24 hours); when ethylene was removed this capability remained high for sometime (more than 24 hours). Norbornadiene, a competitive inhibitor of ethylene action, effectively eliminated the promotive effect of ethylene in tomato fruit. These data indicate that the development of the capability to convert ACC to ethylene in preclimacteric tomato and cantaloupe fruits are sensitive to ethylene treatment and that when these fruits are exposed to exogenous ethylene, the increase in ethylene-forming enzyme precedes the increase in ACC synthase.