Association Between Loss of Leaf Turgor, Abscisic Acid Levels and Seed Set in Two Wheat Cultivars

Abstract

An increase in abscisic acid (ABA) content of the spike and a decrease in seed set of the spike resulted from the withholding of water from the wheat plant during pollen meiosis. The leaf was probably the source of this ABA since spike turgor was maintained whereas leaf turgor was lost. A change in elasticity of the leaf was associated with its loss of turgor (0-0.4 MPa leaf turgor). The correlation with ABA content points to this change in elasticity as a possible pressure-sensing mechanism regulating ABA synthesis at low or zero turgor. For the two cultivars examined, differences in seed set under well-watered conditions were associated with differences in ABA content of the spike. However, complete infertility was not observed and, also, all florets were affected to the same extent. Possibly pollen is sensitive to stress over a range of developmental stages and not solely during meiosis. Alternatively, the effects of stress may linger for some time after rewatering of the plants.