Induction of male sterility in wheat by meiotic-stage water deficit is preceded by a decline in invertase activity and changes in carbohydrate metabolism in anthers

Water deficit during meiosis in pollen mother cells of wheat (Triticum aestivum L.) induces male sterility, which can reduce grain set by 40 to 50%. In plants stressed during meiosis and then rewatered, division of pollen mother cells proceeds normally but subsequent pollen development is arrested 3 or 4 d later. An inhibition of starch accumulation within the pollen grain suggested that an alteration in carbohydrate metabolism or assimilate supply may be involved in pollen abortion. We measured levels of various carbohydrates and activities of key enzymes of Sue metabolism and starch synthesis at different stages of pollen development in anthers collected from well-watered and water-stressed plants. Compared to controls, soluble sugars increased in anthers stressed during meiosis, then decreased at later poststress stages. Sucrose and myoinositol accounted for part of the sugar accumulation. The activity of soluble acid invertase declined 4-fold during the stress period and never recovered thereafter. Sucrose synthase activity during starch accumulation in pollen was also lower in the anthers of plants stressed at meiosis. Stress had little negative effect on the activities of ADP-glucose pyrophosphorylase or soluble and granule-bound starch synthase during starch accumulation in pollen, although at the earlier stages, ADP-glucose pyrophosphorylase activity in stressed anthers was slightly lower compared to controls. The results suggest that carbohydrate starvation per se and inhibition of the enzymes of starch synthesis probably were not responsible for the stress-induced pollen abortion. Instead, an inability to metabolize incoming sucrose to hexoses may be involved in this developmental lesion.