Abscisic Acid Metabolism in Intact Wheat Seedlings under Normal and Stress Conditions

Metabolism of abscisic acid (ABA) was studied in intact seedlings of Triticum aestivum during 14 days. (2-(14)C)-ABA solution (2.5 × 10(-4) M) was applied to the roots of plants for 24 h; after that plants were further grown in nutrient solution. Distribution of radioactivity between ABA and its metabolites was investigated in shoots, roots, and remaining seed parts. In whole seedling as well as in different plant parts the level of free ABA is decreased rapidly during 3 days after application, whereas the level of conjugates rises. Acidic ABA metabolites were detected in low concentration. The growth behaviour of seedlings is correlated strongly with ABA metabolism. ABA application for 24 h inhibits plant growth for three days. If most of the ABA applied is transformed to conjugates the seedlings start to grow rapidly. No evidence was obtained that ABA conjugates are translocation forms or storage forms of ABA. Short time drought stress condition did not alter ABA metabolism in wheat.