UNICONAZOLE-INDUCED CHANGES IN ABSCISIC-ACID, TOTAL AMINO-ACIDS, AND PROLINE IN PHASEOLUS-VULGARIS

Fourteen-day-old bean (Phaseolus vulgaris) plants were soil treated with 100 ml of either 10 mg liter-1 uniconazole ((E)-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol) or 3 mg liter-1 abscisic acid (ABA). Over the next 10 days, the concentration of uniconazole, ABA, total amino acids, and proline in the primary leaves and their stomatal resistance were monitored. In plants treated with exogenous ABA, there was a single transient increase in stomatal resistance with the endogeous concentrations of ABA, proline, and total amino acids increasing to a maximum approximately 2 days after treatment. In the uniconazole-treated plants, the accumulation of uniconazole in the primary leaves was not linear but was biphasic over the duration of the experiments. This correlated very closely to changes in the stomatal resistance. The concentrations of ABA, proline, and total amino acids followed a similar pattern with the first and second peaks occurring 3-4 and 8-9 days after treatment, respectively. These results suggest that the accumulation of ABA may be the direct result of the presence of uniconazole in the primary leaf tissue. Furthermore, the accumulation of proline and other amino acids that have been associated with environmental stress resistance is likely mediated through the uniconazole-induced accumulation of ABA. A radioimmunoassay for the rapid and sensitive quantification of ABA is also outlined. © 1990.