Effects Of Waterlogging On Photosynthesis And Starch Synthesis During Flowering In Wheat

In this experiment,the wheat variety Zhengmai 9023 was used as the test material.After the wheat flowering,the waterlogging treatment was carried out as the waterlogging group(WL,keeping the water layer of 1-2 cm).The normal growth was used as the control group(CK)during for 8 days.The effects of waterlogging on the photosynthetic characteristics of flag leaf,penetration matters,starch synthase and the impact of production were studied.The aim of this study was to clarify the physiological effects of waterlogging on flag leaf and grain at flowering stage,and to provide theoretical basis for deepening and expanding wheat resistance cultivation.The results are as follows:1.The photosynthetic fluorescence parameters and penetration indexes of flag leaves of wheat were significantly affected by waterlogging stress.Compared with the control,the waterlogging treatment decreased the chlorophyll a+b(Chla+Chlb)content and the chlorophyll a/b(Chla/Chlb)values;the net photosynthetic rate(Pn)of flag leaf decreased but the difference was not significant.CO2 concentration(Ci),transpiration rate(Tr)and stomatal conductance(Gs)were not significantly affected,and the decrease of photosynthetic rate was probably caused by non-stomatal limitation.The maximal photochemistry efficiency(Fv/Fm),photochemical quenching(qP)and actual photochemical yield(?PS?)decreased during the waterlogging,and the nonphotochemical quenching coefficient(NPQ)increased,reflecting the light reaction(PS ?)of wheat flag leaves under waterlogging stress was damaged,the initial reaction of photosynthesis was inhibited to a certain extent.The contents of sucrose and soluble sugar in flag leaves and grains were increased,and the content of soluble protein in flag leaves and grains decreased in the early and late stages of waterlogging.2.The wheat flag leaf antioxidant capacity was affected by waterlogging during the flowering period.Flag leaf and grain malondialdehyde(MDA)content,peroxidase(POD)increased.The activity of catalase(CAT)in flag leaves increased,but CAT activity,flag leaf and grain superoxide dismutase(SOD)activity decreased,and the change pattern of flag leaf and grain at different time was different.3.The activity of starch synthase,amylose and amylopectin content and the final yield was affected by waterlogging during the flowering period.The effects of waterlogging on the activity of starch and synthase in wheat flag leaves were different.Compared with the control,the adenosine diphosphate glucose pyrophosphorylase(ADPGase)activity in flag leaf was decreased in the early stage of waterlogging,and the activity of grain ADPGase was decreased.Granule-bound starch synthase(GBSS)in flag leaf increased in the early stage of the waterlogging but decreased in the later period,and the activity of grain GBSS was decreased.The activity of soluble starch synthase(SSS)in flag leaf decreased during the early stage of waterlogging,and the activity of grain SSS was decreased.Starch branching enzyme(SBE)activity in flag leaf decreased during the waterlogging period,and the activity of grain SBE was increased in the early stage of waterlogging but increased in the later period.Starch debranching enzyme(DBE)in flag leaf and grain increased and decreased in the later stage but decreased in the later period.The amylose and amylopectin content of flag leaf increased,and the content of amylose and amylopectin in grain decreased.Waterlogging decreased the panicle weight,1000-grain weight and harvest index of grains at maturity in wheat,but had no significant effect on grain number per spikeIn summary,the waterlogging treatment at flowering stage significantly reduced the ability of flag leaf photosynthetic capacity,flag leaf and grain antioxidant capacity decreased.The activity of the main starch synthase in flag leaves and grains was affected,and the amylose and amylopectin content was further affected,and the yield of wheat ultimately reduced.