Comparison of Elongation Force, Stem Thickness and Evolution of Ethylene in Seedlings of Several Epigeal Leguminous Crops

[摘要] Using an unbonded strain gauge transducer (UT:1 kg type) and a null balancing recorder, the vertical elongation force (Ef) or lifting force of 3-cm tall seedlings in eight epigeal leguminous species grown under darkness at 25°C was measured. Using the same seedlings, hypocotyl diameter (stem thickness) and endogenous ethylene evolution were measured simultaneously. After setting the tip of a seedling against the force receptor, the Ef exerted by the seedling increased with time and reached a maximum after 15-50 hours. The pattern of Ef development differed significantly among the species. The maximum Ef was the largest (about 500 g) in peanut (Arachis hypogaea L.) and the smallest (about 30 g) in moth bean (Vigna aconitifolius Marechal). The mean value for the maximum Ef of a species was positively correlated with seed size (r=0.9636**) and stem thickness at the center portion of the seedlings (r=0.9636**), while each of the maximum Ef per unit mass of seed and per unit stem thickness differed among the species. In all species examined, hypocotyl elongation was inhibited and stem thickness found to be large in the seedlings used for the Ef test. Moreover, in a seedling whose hypocotyl elongation was inhibited, ethylene was increased largely compared with those not inhibited. The ethylene production from a seedling was higher in soybean (Glycine max Merr. cv. Akisengoku), kidney bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata Walp.) and hyacinth bean (Lablab purpureus Sweet) than in peanut, moth bean, mung bean (Vigna radiata R. Wilczek), black gram (Vigna mungo Hepper) and soybean (cv. Asoaogari). It was the lowest in peanut among the species. Thus, it is suggested that, in the seedlings of plant species which produce high ethylene, their hypocotyls become thicker and the Ef exerted by seedlings after bending of hypocotyl become larger. Further, the Ef of a seedling appears to be related intimately with anatomic structure and resistance of bending of hypocotyl.

[学科分类] 农业科学（综合）

[关键词] Elongation force;エチレン;Emergence;下胚軸;Ethylene;出芽;Hypocotyl;抽出力;Leguminous crops;マメ科作物;Seedlings;芽ばえ