Studies on the reduction of the transplanting injury in Japanese persimmon trees. II

Abstract

Japanese persimmon trees make poor growth very often in the first growing season after they are transplanted into the field. It is said that one of the causes of this trouble is due to the delayed and poor growth of new roots from the transplants. In this study, application of potassium α-naphthaleneacetate, a growth regulator, was made in an, effort to overcome this trouble by promoting the new root development of the transplants. Oneyear-old persimmon seedlings were dug up and all their fine roots were trimmed off. Some of the seedlings were treated by soaking their roots in the growth regulator solution of 0.001 to 0.05% for 24 hours (dipping method). Others were treated by applying the solution of 0.005 to 0.01% into the soil once or twice after they were planted in the soil (soil application method). The check plants were dipped in tap water for 24 hours. All the plants were grown in an unheated glass house for protecting them from frost. In June, their roots were washed out for the observation of new root development. The growth regulator treatments accelerated neither the opening of buds nor the unfolding of leaves. The treatments, however, promoted the elongation of new shoots and increased the size of leaves (Fig.1). These effects were significant from an early stage of growth. The treatments induced earlier development of new roots, and markedly increased the number and weight of new roots (Fig. 2). The dipping method was more effective than the soil application method. The higher the concentration of the growth regulator solution, the greater was the effect, up to 0.05%, the highest concentration used in this study.