2,4-Dが大豆の養分吸収に及ぼす影響に就て

抄録

Soybean plants were grown in the nutrient solution of Shive and Robbins (table 1) and at the second trifoliate leaf age sprayed with 500 and 1000 p.p.m. concentrations of Na 2,4-D to the upper parts. Drooping of the plants was quickly followed by twisting of the leaf petioles and bending of the stems.The disappearance of root vitality was observed about 3 days after the treatments. Over two weeks, nutrient absorption with respect to four elements, P, NO_3-N, NH_3-N, and K, was estimated by analyzing the nutrient solntions in which the plants were cultured for 24 hours at pH 6.2. The results may be summarised as follows : (1) Absorption of nutrients decreased rapidly, reaching minimum in about 3 days after the treatments and then showed temporary increase, followed by the second steady decline. The plants treated with 1000 p.p.m. Na. 2,4-D were more remarkably affected than treated with 500 p.p.m. and they could not nearly absorb any of the four elements at the minimum (table 3 and fig. 1-4), (2) Within first 3 days the reduction in absorption was relatively weak with P, and the inhibition persisted most strongly with NO_3-N duriug next 4〜14 days, when the absorption was mainly performed by the numerous initiated roots of the treated plants (table 4). (3) Higher ratios of absorbed cations / anions were noted for the treated plants, due to chiefly a marked inhibition of NO_3-N absorption.