Delayed Maturity of Bean Plants Sprayed With Solutions of 2,4-Dichlorophenoxyacetic Acid of Nonherbicidal Concentrations

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Abstract
Red kidney bean plants were sprayed when the first trifoliate leaf was expanding, using 70% 2,4-D and 30% NaHCO3 acidified with 1 gin. of citric acid/liter. On April 7 (1 wk. after germination) half the plants in a greenhouse study were sprayed with 2,4-D soln. at 10 ppm. The treatment caused slight epinasty of stem and petioles, inhibited top growth, but accelerated root growth. About May 1, the top growth of treated plants was normally vigorous but some of the younger leaves showed toxicity symptoms. At the end of May the treated plants grew more vigorously than untreated ones. In mid-June, the treated plants had a higher number of leaves per plant than untreated plants. The treated plants showed a greater set of fruits. Untreated plants turned yellow at the beginning of June but treated ones remained green about 2 weeks longer. In the field expt., seed was planted May 31 and the plants were treated June 24. A day later, plants sprayed with 100 ppm. showed pronounced epinasty, while only slight epinasty occurred at 10 ppm., and none at 1 ppm. Growth at 100 ppm. was markedly inhibited. At 10 ppm. there was only a slight temporary inhibition. By July, abnormal leaves developed in plots sprayed with 100 ppm. In plots sprayed with 10 ppm., only a few plants developed abnormal leaves. Flowering in the 100-ppm. plots was markedly delayed.
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