Changes in Elongation Force, Stem Thickness and Evolution of Ethylene accompanied with Growth of Soybean Seedlings

[摘要] Using an unbonded strain gauge transducer (1kg) and a null balancing recorder, the vertical elongation force (Ef) or lifting force of 1-, 3- and 5-cm tall soybean seedlings (cv: Akisengoku and Fukuyutaka) grown in darkness at about 25°C were measured. On the same seedlings, diameter at the largest portion of the hypocotyl was measured using a slide caliper. In measuring endogenous ethylene evolution, scedlings were grown in glass cylinders of 2.7 cm in diameter and 25 cm high under darkness at 25°C. To remove the ethylene evolved from the seedling, 2 g of ethylene-acetaldehyde removing agent was put into each glass cylinder. In all the tests, seedlings were grown using sandy loam soil which had been sieved through a 2.38 mm screen and which had about 13% moisture by volume. All the above handlings were performed quickly under dim green light. The Ef exerted by a seedling increased with time after setting the tip of seedling against the force receptor and reached a maximum after 48 to 60 hours. The pattern of Ef development differed a little among the different ages of seedlings. The maximum Ef was largest in 1-cm tall seedling and smallest in 5-cm tall seedling. Hypocotyl elongation was inhibited and hypocotyl diameter became large in those seedlings which were used for the Ef test. Further, in a seedling whose hypocotyl elongation was inhibited, ethylene production was 3-7 times of a seedling not inhibited. When the evolved ethylene was removed using ethylene-acetaldehyde removing agent, hypocotyl thickness was reduced although it was still larger than that of control. It is suggested that, if the hypocotyl elongation is inhibited during emergence by soil particles and crust, the seedlings produce ethylene, and their hypocotyls become thick and their Ef become large.

[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;ダイズ;Soybean seedlings;抽出力