Effects Of Different Covering Models On The Physiological Regulation About Source-Flow-Pool And Yield Formation After Anthesis Of Dryland Winter Wheat

The technique of bundled-straw covering cultivation in wheat in dryland is developed by the Gansu Agricultural University in recent years.Compared to the traditional cultivation without any covering,the cultivation mode can improve 30%of wheat yield by multi-plot field trials for several years,which approached to that in plastic film mulching cultivation.To reveal the physiological mechanism of improvement in wheat yield under the straw strip covering cultivation in the semiarid rain-fed ecological region,a winter wheat variety Longzhong 2 was selected to analyze the differences in physiological characteristics of photosynthesis and antioxidant system of flag leaf after flowering,accumulation and translocation of water soluble carbohydrates（WSC）and its metabolism,grain filling and grain yield under the bundled straw covering cultivation（BS）,the plastic film mulching cultivation（PF）,and the cultivation without cover（CK）.The results are as follows:1.The mulching improved photosynthetic potential,photosynthetic pigment content,photosynthetic parameters and chlorophyll fluorescence parameters of flag leaves after flowering,in which the overall increase amounts under the BS were more than that under the PF.The BS enhanced the light energy capture ability and light energy utilization of flag leaf,which was beneficial for improving the photosynthetic production capacity.Thus the photosynthetic production and its contribution on grain yield was 14.2%and 2.6%higher than the CK,and 8.6%and 1.0%higher than the PF,respectively.The average photosynthetic potential,photosynthetic pigments content,photosynthetic parameters,photochemical efficiency and fluorescence quenching parameters of flag leaf after anthesis were 5.81%,23.12%⁴6.30%,1.73%²6.70%,1.96%⁸.64%higher than those of the PF respectively.2.The BS greatly increased the oxidation resistance of flag leaves.The BS enhanced activities of SOD,POD,CAT and APX by 22.33%and 9.79%,32.69%and 7.89%,10.57%and 9.59%,86.69%and 72.12%,respectively,compared to both PF and CK.The BS significantly eliminated O₂。^-and H₂O₂ and maintained a higher osmotic potential.The membrane lipid peroxidation was average alleviated by 21.01%and 6.92%in growth stages compared with both PF and CK,indicative of the better drought resistance.3.The mulching promoted the WSC synthesis and inhibited its hydrolysis,thereby increasing the WSC,sucrose,fructan content in different organs.The promotion effect in enzyme activity related to WSC under the BS was higher than that under the PF,while the inhibitory effect was reversed.The activity of SS,SPS,SST and SFT associated with WSC synthesis during anthesis-milk stage in the BS was 10.04%¹7.69%of higher than that under the PF.The activity of SNI and SAI related to WSC hydrolysis in BS was 23.97%³6.73%of lower than that under the PF.Therefore,the content of WSC,sucrose and fructosan in BS were 16.66%%,17.98%and 14.49%of higher than that of the PF,respectively.4.The mulching increased the amount of WSC transferred to the grain before and after the anthesis.The total translocation amount of WSC from organs to the grain displayed as PF>BS>CK before anthesis,while as BS>PF>CK after anthesis.The BS significantly increased the post-anthesis contribution rate of WSC to grain weight by 10.65%,in which PF was similar to CK.5.The BS was beneficial to grain filling and thus increased grain weight.The grain-filling duration of main stem in BS prolonged more than three days compared with CK and PF.In particular,the rapid-increase stage of grain-filling prolonged four days.Compared to CK,the average grain-filling rate and the grain weight increased by 12.04%and 5.15%,respectively.6.The BS significantly increased the grain yield by 35.4%compared with CK.In yield components,the spike numbers per unit area was predominant in yield formation(r=0.786^**).The spike numbers per unit area in BS was 59.6%and 46.2%of higher than that in CK and PF,respectively.7.By the analysis of yield relational grade,the yield formation in BS was closely correlated with the positive regulation on POD activity and the synthetic enzymes activity of WSC,and the accumulation of WSC in flag leaf.The relational grade of yield with POD,SST,SS activities and WSC content of flag leaf under the BS was 0.4211,0.7110,0.6139and 0.5081,respectively.As a result,the BS could improve the drought tolerance of dryland wheat,delay the recession source-flow-pool in functional organs,and promote WSC accumulation and transport to grain.In population construction,the BS significantly increased the panicle numbers per unit area and storage capacity of grain kernel,which was better for increasing grain yield.It was suggested that bundled-straw covering cultivation was suitable for popularization and application in arid and semi-arid region of northwest China.