An association between abscisic acid (ABA) content and fertility is demonstrated in the wheat spike. ABA contents are significantly higher and the rate of ABA degradation is almost halved in male sterile spikes from the chromosomal mutant, Cornerstone. On a dry weight basis the anther contains disproportionately more ABA than the rest of the spike. Spike ABA is high before pollen meiosis and drops within 3-6 days (2 to 20-fold) both in the Cornerstone material and in a normal cultivar.