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This manuscript reports that for tulip bulbs ( Tulipa gesneriana L. 'Apeldoorn'), simultaneous application of methyl jasmonate (JA-Me) with gibberellic acid (GA) increases gum formation in the bulbs, compared to JA-Me applied alone. After the dry scales of the bulbs were removed, the bulbs were treated with JA-Me and GA starting from the beginning of July 20 until November 30. Treated bulbs were stored in a laboratory room in natural light conditions. Gums produced by each treatment were weighted one month after treatment. JA-Me, at concentrations of 0.5 and 1.0% in lanolin, was applied alone, and also applied simultaneously with GA at concentrations of 0.25, 0.5 and 1.0% in lanolin. All the concentrations of GA applied simultaneously with JA-Me, substantially stimulated gum production in tulip bulbs. The production of gums decreased gradually from the beginning of October. The possible mode of action of GA to stimulate gum production in tulip bulbs is also discussed. The focus is on sugar metabolism and ethylene production.
Mango (Mangifera indica L.) is a highly popular tropical fruit. One of the factors causing the low production of mango is fruit drop. Many factors cause fruit drop, one of them being a phytohormonal imbalance. The objective of this research was to compare the content of indole-3-acetic acid (IAA), 1-amino cyclopropane-1- carboxylic acid (ACC), and carbohydrate between persistent and pre-abscission fruits of two cultivars Gadung 21 and Lalijiwo. Pre-abscission fruit had lower IAA and total sugar, but higher ACC and starch than persistent fruit for both cultivars.
The single-gene male-sterile 7B-1 mutant in tomato (Lycopersicon esculentum Mill.) shows reduced de-etiolation of hypocotyl growth, has an elevated level of endogenous abscisic acid (ABA) and reduced amounts of growth-active gibberellins (GAs), is supersensitive to exogenous ABA, and is resistant to abiotic stresses in light but not in the dark. The existence of crosstalk between light signaling and plant hormones, and the interaction of ABA and GA biosynthetic pathways with ethylene, led us to investigate the possible role of ethylene in the 7B-1 mutant. In the dark, 7B-1 seedlings exhibited the normal triple response to 1-aminocyclopropane-l-carboxylic acid (ACC), an ethylene precursor, similar to the wild type. In light, however, hypocotyl growth of mutant seedlings was more sensitive to ACC but less sensitive to the inhibitors of ethylene’s action, such as silver thiosulfate, than the wild type. The 7B-1 mutant seedlings produced reduced levels of ethylene, which could account for the increased sensitivity to exogenous ACC. The mutant leaf discs also contained higher chlorophyll content and showed greater chlorophyll degradation in response to ACC than the wild type, and these could also be related to low ethylene production by the mutant. Fluridone, an inhibitor of ABA biosynthesis, countered the ACC-induced inhibition of hypocotyl elongation, and it also restored the wild-type phenotype in 7B-1 plants. The results suggest that the reduced de-etiolation of hypocotyl growth and the increased sensitivity of the mutant to ethylene in light are due to reduced ethylene production, which in turn may be related to high endogenous ABA. The data presented support our earlier findings that the 7B-1 mutant has a defect in light perception which affects both hormonal sensitivity and endogenous levels, thereby affecting hypocotyl and shoot growth.
Application of 1-naphthaleneacetic acid (NAA) or 1-aminocyclopropane-1-carboxilic acid (ACC) to maize roots growing in hydroponic solution inhibited root elongation, and increased radial growth, but the responses to those treatments differed in degree. Auxin was more effective than ACC as an elongation inhibitor and root swelling promoter. Whereas NAA fully inhibited elongation and maintained swelling over 48 h, ACC inhibited elongation partially (50%) and only promoted swelling for 24 h. It is well-known that auxin, like ACC, promotes ethylene production, but similar levels of ethylene production reached by means of NAA or ACC treatments did not elicit the same response, the response being always stronger to NAA than to ACC. These results suggest that the effect of auxin on root growth is not mediated by ethylene. Elongation and swelling of roots appear to be inversely related: usually a reduction in elongation was accompanied by corresponding swelling. However, these two processes showed different sensitivities to growth regulators. After 24 h treatment with 0.5 μM NAA or 5 μM ACC, root elongation was inhibited by 90% and 53% respectively, but the same treatments promoted swelling by 187% and 140% respectively. Furthermore, 1 μM ACC was shown to promote inhibition of root elongation without affecting swelling. The ethylene antagonist STS (silver thiosulfate) did not affect elongation in control or NAAtreated roots, but increased ethylene production and swelling. These results indicate that longitudinal and radial expansion could be independently controlled.
Methyl jasmonate (MeJA) was found to reduce spore germination, hyphal and mycelial growth in Alternaria alternata (Fr.) Keissl. The addition of ethephon or 1-aminocyclopropane-1-carboxylic acid (ACC), ethylene precursor, together with MeJA to the culture medium resulted in a promotion of all developmental stages of the fungus; these compounds partially or completely reversed the inhibition due to MeJA depending on the concentrations applied. MeJA alone had no effect on ethylene production by mycelium, but after 6 days of incubation in the presence of ACC, emanation of this gas increased significantly. Ethylene is involved in reversing the inhibition of A. alternata due to MeJA.
Effects of different temperatures on bud break and 1-aminocyclopropane-1-carboxylic acid (ACC) content were determined by using potted two-year-old ‘Akatsuki’ peach trees. One group of trees were subjected to 1°C for four weeks and then transferred to a growth chamber at 24 °C, while the other was kept at 24 °C throughout the experiment. After four-week temperature treatments floral and vegetative bud break were evaluated weekly and bud break percentage was calculated. Bud break was greater under 1 °C than 24 °C in both November and December. The time required to release buds from dormancy was shorter in December than November. In November ACC content in peach buds increased after one and two weeks, then decreased in the forth week under both treatments. However, in December ACC content after two and four weeks showed a similar trend under 1 °C and a reverse trend under 24 °C. It was higher under low temperature treatment. These data indicate that chilling requirements for bud break of peach seems to be associated with the promotion of ethylene biosynthesis caused by low temperature stress.
Germination of tomato cv. New Yorker seed is inhibited at 35 °C. This thermoinhibition was partially counteracted by application of GA4+7 alone, the compound applied in combination with ACC or ethephon markedly enhancing the process. The latter compound alone was not able to induce germination at 35 °C. Thermoinhibition of seeds at 35 °C was also counteracted by fluridone, an inhibitor of ABA biosynthesis. At 25 °C, an optimal temperature, ABA inhibited germination of New Yorker seeds. Although another known growth inhibitor MeJA, when applied at an optimal temperature (25 °C), had also a slightly inhibitory effect on germination of those seeds and clearly delayed the process, inhibitors of its biosynthetic pathway (ibuprofen, indoprofen, antypiryne and salicylic acid) did not remove thermoinhibition at 35 °C. An increase in endo-β-mannanase activity after 24 hours of incubation at 35 °C was observed in the seeds incubated in the presence of gibberellins, ACC, ethephon, fluridone used alone and in combinations, but it was not clearly correlated with the effects of these compounds on alleviation of seed germination. However, fluridone present in the same incubation medium at 35 °C with ABA was able to counteract the inhibitory effect of ABA on endo-β-mannanase activity. The results of our study suggest that gibberell ins, ethylene (produced from ACC or ethephon) and ABA, but not jasmonates, regulate tomato seed germination at supraoptimal temperatures. Alleviation of thermoinhibition of New Yorker seed germination by plant growth regulators and fluridone is partially associated with their controlling endo-β-mannanase activity.
One of the prime precursor for ethylene synthesis - L-methionine and the inhibitor of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) - Co2+- were tested for their effects on sex expression and development of Anemia phyllitidis fern gametophytes. Five concentrations of both chemicals (0, 10, 25, 50, 100 μM) were analysed with reference to antheridia and archegonia formation, number and size of cells as well as thalli length using the three-zone model of gametophyte structure. Both substances, however at different concentrations, enhanced the number of GA3-induced antheridia and similarly stimulated the cell number and inhibited thalli length. Both of them at 100 μM concentrations without GA3 induced meristematic area formation while methionine also induced archegonia in the apical parts of gametophytes. These findings correspond with the previous observations concerning the important role of ethylene synthesis precursor (ACC) in controlling gibberellic acid-induced male sex expression in ferns and broaden the knowledge about the mechanisms of fern gametophyte development.
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