Effects of abscisic Acid on growth, RNA metabolism, and respiration in germinating bean axes.

The effect of abscisic acid on growth, respiration, the ATP pool, and rate and amount of RNA synthesis in aseptically cultured axes of Phaseolus vulgaris during the first 24 hours of germination has been measured in experiments where the duration of abscisic acid application and its concentration have been varied. At concentrations from 10(-7) to 10(-4)m, abscisic acid inhibits synthesis of RNA with maximal inhibition (80%) at 10(-5)m. RNA synthesis is inhibited by abscisic acid at all times examined (12, 18, and 24 hours), but the extent of inhibition is maximal at 18 hours. In 18-hour axes RNA synthesis is inhibited 42%, ATP pool size is reduced 3%, and O(2) consumption is decreased by 6% after 75 minutes of abscisic acid treatment. Inhibition of RNA synthesis is complete by 2 hours of treatment with abscisic acid, and recovery to near control levels occurs by the 3rd hour after removal from abscisic acid.