Relationships between structure and growth-promoting activity of the gibberellins and some allied compounds, in four test systems
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Euphorbia motuogensis M. T. Li, X. Z. Lan, H. P. Deng & W. L. Zheng, sp. nov., a new species from Motuo, Tibet, China, is described and illustrated here. It is closely similar to Euphorbia sikkimensis in having terete root, alternate leaves, well-developed pseudoumbellate inflorescence, cyathium, smooth and glaborus capsule, but Euphorbia motuogensis is clealy distinguishable by its pilose stems, involucral leaves color, secondary involucral leaves absent, cyathophylls number and color, and five similar glands. Furthermore, molecular phylogenetic analyses of sequences from both nuclear ribosomal ITS confirm that this species is distinct from morphologically similar species in this subgenus.
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Apical 2-cm hypocotyl segments from seedlings of a “short-hypocotyl” cultivar Amsoy 71, like whole seedlings, evolve about twice as much ethylene at 25°C as at 30°C. Segments consisting of two cotyledons and an attached epicotyl evolve ethylene at low rates at both 25°C and 30°C. Hypocotyl segments from seedlings of Cutler 71 also show enhanced ethylene evolution at 25°C. Hypocotyl segments from Corsoy, a “long hypocotyl” cultivar, however, evolve ethylene at low rates at both 25°C and 30°C. Wounding of Amsoy 71 hypocotyl segments does not increase their ethylene evolution. Ethylene evolution at 25°C is reduced and the short-hypocotyl phenomenon is reversed by partial (50%) removal of Amsoy 71 cotyledons at planting time.
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INTRODUCTION Hypocotyl elongation of young seedlings is an important response affected by both endogenous developmental programs and exogenous signals, such as light quality and quantity. When a seed germinates in the dark (as it might if it were buried in soil), the hypocotyl extends and the cotyledons remain folded under a protective hook. When the seedling reaches the light, the rate of hypocotyl elongation is inhibited, and vegetative development is initiated. This protocol describes the measurement of hypocotyl lengths in freshly germinated seedlings.
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The effect of removal of cotyledonary tissue on the subsequent hypocotyl elongation at 25 C of four soybean ( Glycine max L. Merr.) cultivars was studied. Following a 24‐hour imbibltion period, cotyledonary tissue was removed from seed of “short” hypocotyl ‘Amsoy’ and ‘Beeson’ and “long” hypocotyl ‘Corsoy’ and ‘Hawkeye.’ Seed were then grown on paper towels for 7 days at 25 or 31 C. Inhibition of Amsoy and Beeson hypocotyl elongation at 25 C was reduced by this technique. Hypocotyl dry weight decreased, but hypocotyl length increased with increasing percentage removal of cotyledons. Removal of 50% gave the greatest reversal of the inhibition; at 75% removal, limited food reserves apparently decreased hypocotyl length. Hawkeye and Corsoy hypocotyl length did not increase with increasing cotyledon removal. Resuits suggested that inhibition of Amsoy and Beeson hypocotyl elongation at 25 C may be due to an inhibitory substance, or its precursor, located in the cotyledons.
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The effectiveness of breeding for soybean ( Glycine max (L.) Merr.) hypocotyl length at 25 C was evaluated by examining segregation from crosses between long, intermediate, and short hypocotyl cultivars and performance of the parent cultivars. Progeny were evaluated in F 1 and F 2 as individual seedlings and in F 3 as the mean of 24 seedlings for each F 2 line. All tests for hypocotyl length were conducted in the dark in growth chambers maintained at 25 ± 1 C. Evaluation of individual seedlings for the parent cultivars indicated that there was an environmental influence on hypocotyl length, particularly for the intermediate cultivars. There was little overlap in the single plant distributions for long and short hypocotyl cultivars, but the distributions for intermediate cultivars had considerable overlap. Progeny from crosses between long hypocotyl cultivars were similar to the parents in hypocotyl length. Crosses of long ✕ intermediate and long ✕ short parents had segregation typical of a major gene with dominance for long hypocotyls. The F 2 lines in F 3 generally were within the range of the parents for intermediate ✕ intermediate, intermediate ✕ short, and short ✕ short crosses. Selection for genetic differences in hypocotyl length at 25 C is possible. To select for long hypocotyl genotypes, crosses should include at least one long hypocotyl parent. In crosses involving only intermediate and short hypocotyl parents, transgressive segregates may be found that exceed the length of the best parent; however, the frequency of superior segregates in such crosses probably will be low. Selection for hypocotyl length on a single plant basis is hampered by environmental effects. In a segregating population, selection for long hypocotyl genotypes on a single plant basis will eliminate many of the short hypocotyl genotypes, but will include some of the intermediate genotypes. A progeny test is the best way to evaluate a genotype's genetic potential for hypocotyl length.
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In this paper, we used plant growth regulators, such as gibberellin and ethephon to treat fruit sugarcane Qiantang5 respectively. The results show that the spraying of gibberellin on the plants with its concentration of30g/year.667m2 has positive effects on most agronomic characters, such as growth speed, plant height, validstalks, brix, sucrose content and yield. The residue of gibberellin is 0.05mg/kg. However, ethephon has nopositive effects on agronomic characters except the growth speed.
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Development of dark-grown "Clark" soybean (Glycine max [L.] Merr.) seedlings is abnormal at 25 C but normal at 20 and 30 C. At 25 C, hypocotyls swell and fail to elongate normally; lateral root formation and seedling ethylene evolution are enhanced.Co(2+) promoted hypocotyl elongation of etiolated "Clark" soybean seedlings by 28% when grown at 25 C. The same growth-promoting concentration reduced hypocotyl thickness and primary root elongation by 28 and 43%, respectively. Co(2+) inhibited ethylene production both of intact seedlings and of apical 1-centimeter hypocotyl segments with attached epicotyls and cotyledons by 65 and 60%, respectively. These results suggest that Co(2+) exerts its effects on the hypocotyl growth by inhibiting ethylene production, and also confirm our previous conclusion that abnormal ethylene production at 25 C is responsible for the inhibition of hypocotyl elongation and for its swelling.
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The gibberellins (GAs) are endogenous regulators of plant growth. Experiments are described here that test the hypothesis that GA regulates hypocotyl growth by altering the extent of hypocotyl cell elongation. These experiments use GA-deficient and altered GA-response mutants of Arabidopsis thaliana (L.) Heyhn. It is shown that GA regulates elongation, in both light- and dark-grown hypocotyls, by influencing the rate and final extent of cellular elongation. However, light- and dark-grown hypocotyls exhibit markedly different GA dose-response relationships. The length of dark-grown hypocotyls is relatively unaffected by exogenous GA, whilst light-grown hypocotyl length is significantly increased by exogenous GA. Further analysis suggests that GA control of hypocotyl length is close to saturation in dark-grown hypocotyls, but not in light-grown hypocotyls. The results show that a large range of possible hypocotyl lengths is achieved via dose-dependent GA-regulated alterations in the degree of elongation of individual hypocotyl cells.
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The present experiments were conducted to investigate the variability of hypocotyl elongation among the major soybean varieties by checking several conditions. The results obtained are summarized as follows. The rate of hypocotyl elongation is the highest during the day from 3.0 to 3.5 after seeding. It follows that it may be reasonable to evaluate the hypocotyl elongation of soybean seeds by comparison of hypocotyl length. And the tested 15 major cultivars could be classified as follow ; long ; Eunhakong, Janggyungkong and Bokwangkong, medium ; Namhekong, Dangyung-kong, Danyubkong, Milyangkong, Dugyukong, Paldalkong, Mangunjoseng, Namchunkong and Seal kong, short ; Gwanggyo, Begunkong and Jangbegkong. The hypocotyl elongation in small seed is longer than large seed. Correlation coefficients(r) for the relationships between 100 seed weight and hypocotyl elongation is -0.2506** . As the rising temperature, the hypocotyl length is elongated, and longest at the range of 30 to 35~circC . The effects G A3 hastened the hypocotyl elongation of soybean seed, and ABA, Kinetin and BA inhibit it, and that of those in short hypocotyl cultivars are higher than long hypocotyl cultivars. Hypocotyl length of long hypocotyl cultivars are longer than that of short hypocotyl cultivars under high temperature pre -treatment.t.
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