Possible role of abscisic acid in reducing seed set in water-stressed wheat plants

Abstract

One of the primary effects of water stress on grain yield in wheat is the reduction of the number of seeds set per spikelet through an increase in male sterility^1,2. However, little is known of the relationship between loss of pollen viability and the water relations of the developing spikelets, so that it is not known whether the effect of water deficit occurs as direct dehydration of the anther or by some other means. We report here that seed set may be reduced by water deficits which cause leaf wilting but have no effect on spikelet turgor or relative water content. This raises the possibility that abscisic acid (ABA), which is known to increase substantially when the leaf wilts^3,4 and to modify developmental processes in plants⁵, is involved in the processes causing floret infertility. In support of this hypothesis we show that reductions in seed set due to water stress are accompanied by increases in endogenous ABA in both leaf and spikelet, and that foliar application of synthetic ABA at the stage of meiosis also reduces seed set and causes malformation of pollen grains and anthers.