Vitality of primed rice seeds sown under prolonged dry soil conditions in an upland field

Abstract

During rainfed upland rice (Oryza sativa) cultivation, unpredictable drought events can hinder the rice growth. Although drought tolerance is a reported effect of seed priming treatment, we hypothesized that plants from primed seeds would die because they would begin to emerge in dry soil. We also expected that nonemerged primed seeds would show decreased seed vigor because their metabolism was activated by priming before sowing. Therefore, we investigated the vigor of hydroprimed and nonprimed seeds during prolonged drought after sowing during upland rice cultivation. A field experiment was conducted on a rainfed upland field that had insufficient rainfall at the beginning of the season. Plant emergence, establishment, and vigor in resown nongerminated seeds were also investigated. A subsequent growth chamber experiment was conducted to investigate the relationship between sown seed deterioration, soil moisture, and temperature. Contrary to the hypothesis, plants from primed as well as control seeds could survive under prolonged drought after emergence. In the nongerminated primed seeds, oxidative damage was increased. However, the percentage of plant emergence in resown seeds did not differ between treatments. Overall, the performance of primed seeds was better than or similar to that of the control seeds. In conclusion, primed seeds have advantages even under extreme drought conditions in rainfed upland fields.