Effects Of Pre-Anthesis Waterlogging Hardening On Grain Yield And Quality Formation In Wheat Under Post-Anthesis Waterlogging And Its Physiological Mechanism

Waterlogging is one of the major limiting factors influencing wheat(Triticum aestivum L) production. The period between anthesis and maturity is critical for grain yield and quality formation. Then, post-anthesis waterlogging significantly reduced grain yield and worsened quality. This article attempts to discuss effect of pre-anthesis waterlogging hardening on waterlogging tolerance during post-anthesis waterlogging in wheat and its physiological mechanism. In this study, wheat plants were subjected to three times of 2-day waterlogging pretreatments at three pre-anthesis stages (seven-leaf stage, nine-leaf stage and heading period), and then followed a 7-day post-anthesis waterlogging stress from 7 days after post-anthesis (DAA) in a pot culture experiment. Thus, four treatments were established from 7 DAA:(1) WW, pre-anthesis waterlogging hardening and post-anthesis waterlogging; (2) WC, pre-anthesis waterlogging hardening and post-anthesis non-waterlogging; (3) CC, non-waterlogging stress during both pre-anthesis and post-anthesis; (4) CW, pre-anthesis non-waterlogging hardening and post-anthesis waterlogging. The performances of flag leaf photosynthesis, chlorophyll fluorescence traits, antioxidant enzymatic activity and carbon and nitrogen metabolism were then investigated. And further studies in grain yield and quality physiology of wheat. The main results were as follows:1. Pre-anthesis waterlogging hardening improved flag leaf photosynthetic capacity in wheat under waterlogging during grain fillingCompared with non-prehardening treatment, pre-anthesis waterlogging hardening enhanced effectively photosynthetic capacity in wheat flag leaf under waterlogging during grain filling, by increasing stomatal conductance (Gs) and transpiration rate (Tr) and maintaining higher SPAD value, protecting of photosystemⅡand enhancing its photochemical conversion of absorbed light energy via maitainance of high PSⅡmaximum photochemical efficiency (Fv/Fm), ratio of variable fluorescence to original fluorescence (Fv/Fo), actual photosynthetic efficiency(ΦPSⅡ).2. Pre-anthesis waterlogging hardening enhanced flag leaf antioxidant capacity in wheat under waterlogging during grain fillingPre-anthesis waterlogging hardening enhanced effectively antioxidant capacity in wheat flag leaf under waterlogging during grain filling, by increasing activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), and reducing accumulation of malondialdehyde (MDA) and activity of peroxidase (POD), in comparison with the non-prehardening treatment. In addition, pre-anthesis waterlogging hardening decreased MDA content, O2- release rate and POD activity and increased SOD activity in chloroplast and relative water content (RWC) and soluble sugar content in flag leaf.3. Pre-anthesis waterlogging hardening regulated carbon and nitrogen accumulation and redistribution, advanced grain yield and affected grain and flour quality in wheat under waterlogging during grain fillingCompared with non-pretreatment, pre-anthesis waterlogging hardening improved effectively grain dry matter accumulation in wheat under waterlogging during grain filling, by enhancing dry matter accumulation after anthesis and its contribution to grain mass and reduced grain protein content and its accumulation, as a result of depressing redistribution amount of pre-anthesis accumulated nitrogen (NRA) and its contribution to grain nitrogen. Pre-anthesis waterlogging hardening significantly increased 1000-kernel weight, and consequently improved grain yield of wheat under a sever post-anthesis waterlogging, compared with the non pretreated plants. Pre-anthesis waterlogging hardening also caused significantly reductions in grain total protein, globulin, dry gluten and wet gluten contents, and sedimentation volume, while resulted in increases in grain albumin, gliadin, glutelin, compared with the non pretreated plants. Pre-anthesis waterlogging hardening increased contents of amylose and total starch and falling number, and enhanced peak viscosity, hold trough, breakdown, final viscosity, set-back and peak time. However, Pre-anthesis waterlogging hardening did not significantly affect the pasting temperature.In conclusion, pre-anthesis waterlogging hardening improved photosynthetic and antioxidant capacity in wheat flag leaf and regulated effectively carbon and nitrogen metabolism under waterlogging during grain filling. Finally, pre-anthesis waterlogging hardening improved markedly grain yield, compared with the non pretreated plants, while it affected grain quality.