Waterlogging pretreatment during vegetative growth improves tolerance to waterlogging after anthesis in wheat

The interaction of multiple waterlogging events during vegetative growth (at the seven- and nine-leaf stage, and at heading) to a waterlogging event during the generative growth stage was studied in wheat (Triticum aestivum L. cv. Yangmai 9). Waterlogging before anthesis was found to effectively enhance tolerance to a waterlogging event after anthesis, as indicated by: (1) increasing net photosynthetsis (P(N)), stomatal conductance (g(s)) and transpiration (Tr) and maintaining high SPAD (soil plant analysis development) values; (2) enhancing use-efficiency of absorbed light energy in the stressed plants due to high maximum and actual quantum yield (F(v)/F(m), Φ(PSII)); (3) increasing activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT); (4) enhancing dry matter accumulation after anthesis and its contribution to grain mass, which further resulting in significantly improved grain yields. The results indicate that hardening by waterlogging applied before anthesis can effectively improve the tolerance of wheat to waterlogging events occurring during the generative growth stage.