Response Of Different Light Conditions On Photosynthetic Characteristics, Starch Components And Quality In Wheat (Triticum Aestivum L.)

Different genotypes of wheat varieties were used in the experiment of shading with different intensity and period after flowering,wheat flag leaf photosynthetic characteristics,grain yield,the activity of starch synthesis key enzyme,starch accumulation and physical and chemical characteristics of weak light stress response were studied.The results showed that:The chlorophyll a and chlorophyll b,total chlorophyll content,and the ratio of chlorophyll a/b in wheat flag leaf increased after shading to adapt to the decrease of photosynthesis.The net photosynthetic rate,stomatal conductance and transpiration rate of wheat flag leaf showed a trend of decrease.The SPS and SS enzyme activities in wheat flag leaf decreased,which showed that weak light was bad for the synthesis and the sucrose degradation.The curves of the two kinds of enzymes had different peaks with wheat growth,and the highest activity appeared in the 15 days after shading.The SPS and SS activities were higher in Lunxuan987 than Nongdanuo50206.The biological yield,grain yield and economic coefficient of Lunxuan987 and Nongdanuo50206 decreased significantly with the reduced light intensity.The wheat grain amylose,amylopectin and total starch content significantly decreased by different intensity shading after flowering.After flowering 15 days,the rate of accumulation and components of starch were the fastest.The rate of amylose to amylopectin increased with the decreasing light intensity in full ripeness period.The volume and surface area of wheat starch distributed in bimodal curves in full ripeness period with shading in different stages and different intensity light after flowering,the amount was distributed in unimodal curve.With different shading intensity,the ratios of the volume,the surface area and the amount of B-type were decreased significently under treatments of earlier stage and later period,but medium-term treatments promoted the ratios of A-type.The wheat starch crystal type was not affected by light intensity decrease after flowering.The effect of Shading onwheat starch gelatinization properties and thermodynamics properties was significantly,and the effects changed with the stages of shading and gentypes.The amylose content and the ratio had negative correlation with the peak viscosity,valley viscosity,slack value,peak time and pasting enthalpy,but had positive correlation with the final viscosity and rebound value.The amylopectin content had significant positive correlation with the peak viscosity,slack,pasting temperature,peak time and pasting enthalpy,and had negative correlation with the final viscosity and rebound value.