Integrative signaling of hydrogen peroxide and gibberellin on Zn-mediated alleviation of thermodormancy in sorghum seeds

Abstract

Increasing global temperatures could result in decreasing crop production by decreasing seed germination in the field due to thermodormancy acquisition. Certain metals appear to modulate seed thermodormancy, although the exact mechanisms of that effect have not yet been elucidated. We report here the effects of Zn on the thermodormancy of sorghum seeds. Seeds treated with 0 or 200 mg Zn L−1 were germinated at optimal (30°C) and supra-optimal (40°C) temperatures and their germinability and oxidative stress markers were evaluated. The integrative effects of Zn, abscisic acid (ABA), gibberellin (GA), and H2O2 on the physiology of seed thermodormancy were examined. The supra-optimal germination temperature (40°C) induced seed thermodormancy, which was, however, alleviated by treatment with 200 mg Zn L−1. Thermodormancy acquired at supra-optimal temperatures in sorghum seeds must reflect de novo synthesis and accumulation of ABA. Although Zn treatment did not prevent ABA accumulation, it increased the activities of mitochondrial ETC enzymes and decreased the antioxidant enzymes' activity, leading to the accumulation of H2O2. By increasing mitochondria activity and H2O2 production, Zn may induce GA synthesis and alleviate thermodormancy in sorghum seeds. The pretreatment of sorghum seeds with Zn may therefore improve seed germination and assure increased crop performance under normal (30°C) or rising (up to 40°C) temperatures.