Effect of Phenylacetic Acid on the Growth of Tomato Plants

Abstract

MUCH interest has been taken in the action on the growth of plants of various organic substances which has been described by the workers at the Boyce Thompson Institute^1,2. They apply these substances in lanolin preparations to plants, or as a water solution added to the soil or injected into the stem; the main responses of the treated plants being epinasty of the leaves, swellings and proliferations of the stems and petioles, and formation of roots on or near the treated part. In the course of some tests carried out at East Malling Research Station, using phenylacetic acid, I sprayed a batch of tomato plants with a 0.1 per cent solution in water, while control plants were sprayed with water containing a little alcohol. The solution was prepared as described by Hitchcock and Zimmerman³. By the spray method, the amount of growth substance applied can be fairly accurately controlled. Entry was very rapid; epinasty of the leaves being visible after one hour in a greenhouse at a temperature of about 20° C. The plants were treated in the morning, and by the next day the leaves had fully recovered; moreover, very little stem bending had occurred, showing that the distribution of the growth substance was uniform throughout the stem. The treatment was continued daily, and groups of plants were harvested weekly; the fresh and dry weights being determined. Fig. 1 shows a treated and a control plant at the end of two weeks.