Effects of indole-3-butyric acid on the germination and growth of Glycine max (L.) Merr.

Abstract

The impact of indole-3-butyric acid (IBA) on the germination of pella '86' soybean (Glycine max (L.) Merr.) was studied. Indole-3-butyric acid treatment had an inhibitory or stimulatory effect on germination depending on the concentration of the solution used. It was found that with no pretreatment (soaking), IBA could stimulate germination at a range of concentrations of about 0.001% - 0.0001%. On the other hand, treatment at concentrations above this range will inhibit germination; for example, using a 1% solution totally inhibited germination. Treatment of the seeds with hormex or lowering the concentration of indole-3-butyric acid below the optimum range had no (statistically significant) effect on germination. Tests showed that the inhibitory effects of 0.01% - 1% indole-3-butyric acid could be reversed if a nonindole-3-butyric acid solution with the same concentrations was used. Soaking time had an inhibitory effect on germination, and percentage germination was inversely proportional to the soaking hours. Soaking the seeds in a .0001% solution of indole-3-butyric acid for 1, 2, 4, 12, and 24 hours reduced percentage germination from 62.5 (no soaking) to 28.1, 18.75, 15.62 and 4.7 respectively. Indole-3-butyric acid treatment at a concentration of 0.0001% resulted in a few roots which rapidly became long and established fibrous root systems. Treatments at higher concentrations (.01% and 0.001%) on the other hand, produced a very dense, thick and bushy root system. However, as the concentration of IBA in the solution was reduced, the root system gradually changed to that developed under distilled water (control) treatment. The impact of treatment with Hormex on germination was found to be statistically insignificant. However, only tests using Hormex provided information on amount of indole-3butyric acid absorbed by the root system. Tests show that indole-3-butyric acid absorbed by the roots ranged from 21.68 to 2.83 X 10-3 mg of IBA per one gIn of wet plant tissue.