Effect of Spray Applications of 2,4-Dichlorophenoxyacetic Acid on Subsequent Growth of Various Parts of Red Kidney Bean and Soybean Plants

Abstract

Young red kidney bean and soybean plants were sprayed with 2,4-D at rates of 0.1, 0.01, and 0.001 g. per square yard, and the effects of the compound on the various plant parts were studied. The increased fresh wt. of hypocotyls and 1st internodes of treated plants was due mostly to increased water content. Primary leaves of treated plants were much heavier than those of controls. Total wts. of trifoliate leaf blades, trifoliate leaves, and weight of plants above 2d node were shown to be excellent criteria for studying the relative inhibitory or stimulating action of growth regulators on kidney beans. With soybeans, fresh wt. of trifoliate leaf blades was the most sensitive criterion. The growth in length and width of certain leaflets was inhibited by the regulator. With soybeans, the 2 lower rates of application significantly increased wt. of roots at 16 days after treatment. The growth regulator delayed the onset and decreased the amt. of pod formation.