Photosynthetic adaptation mechanisms of waterlogged wheat (Triticum aestivum) at flowering under exogenous nitric oxide donor application

The effects of nitric oxide (NO) on the photosynthetic adaptation mechanisms of wheat plants in waterlogging during the flowering stage are poorly understood. Field and pot experiments using two cultivars were conducted with three treatments: waterlogging (WL), waterlogging plus NO donor sodium nitroprusside (WLsnp), and adequate water (CK). The results indicated that the WLsnp and CK treatments exhibited significantly higher 1000-kernel weight and yield than the WL treatment because of high photosynthetic potential(P<0.05). We found that the photosynthetic performance, including photosynthetic rate (P-n), stomatal conductance (g(s)), mesophyll conductance (g(m)), carbon dioxide concentration at the carboxylation site (C-c), maximum carboxylation rate (V-cmax), maximum electron transfer rate (J(max)), actual electron transfer rate (J), actual PSII efficiency (Phi(PSII)) and potential maximum efficiency in PSII (F-v/F-m), was significantly improved in the WLsnp treatment compared to the WL treatment, both during waterlogging and after de-waterlogging. Little difference was observed in the photosynthetic performance between the WLsnp and CK treatments during waterlogging for cultivar YM15 and after de-waterlogging for cultivar YM24. Further analysis indicated that g(s), g(m) and J were identified as key physiological indicators that synergistically regulate P-n of waterlogged wheat plants. Overall, the improvement of wheat's waterlogging resistance capacity after spraying NO is mainly related to high g(s), great g(m), and high J.