Temporal Changes in Abscisic Acid Concentration in Dormant and Non-Dormant Seeds of Wheat (Triticum spp.) Genotypes

Little is known about the levels and physiological role of endogenous abscisic acid (ABA) during after-ripening and germination. Genetic variants for ABA content were investigated to account for the role of ABA in the persistence of seed dormancy. In this study, genotypic variation in ABA contents at Zadok’s Growth Stage 92 (ZGS 92), temporal changes in ABA during two physiological stages (after-ripening and water uptake), and responsiveness of wheat seed to applied ABA at different concentrations, of two tetraploid and two hexaploid wheat genotypes were examined during 1996 and 97. A combined analysis of variance indicated no significant differences in ABA among genotypes at ZGS 92. During the early stages of germination, endogenous ABA in the caryopses of the four wheat genotypes was analyzed. The results showed a transient increase in ABA content (up to 4 hours) occurring first during imbibition, followed by a decline up to 12 hours and an increase thereafter. ABA declined in all genotypes during seven weeks of after-ripening (dry storage). The four genotypes had reductions in ABA up to 4 weeks of after-ripening. An increase in ABA was observed during the fourth and fifth weeks of after- ripening with a decline after seven weeks. ABA had a little effect on germination index at the lower temperature (10 °C). Our results suggested that wheat grains are able to synthesize ABA during imbibition. However, no significant differences between dormant and non-dormant genotypes were detected. A decrease in ABA during after-ripening could have a role in loss of seed dormancy