Effects Of Staged Drought Stress On Wheat Physiological Characteristics And Yield Structure

In recent years,regional agricultural disasters caused by frequent occurrences of extreme weather and climate events such as global droughts and rainstorms have greatly hindered agricultural production and development.As one of the main food crops in my country,wheat clarifies the impact of different climatic conditions on its physiological parameters.It is very urgent for disaster prevention and mitigation,and is of great significance for creating a resource-saving ecological agriculture.Combined with the national conditions of water shortage in China and the specific monsoon climate characteristics,this article selected'Wanmai 68'as the research object,and set up four different water treatments under the conditions of artificial rain cover.They are DN?returning period-Drought stress at the beginning of flowering,flowering at the beginning of flowering-maturity?,ND?green water at the beginning of flowering-normal flowering,drought stress at the beginning of flowering-maturity?,DD?drought stress at full growth?.Collect photosynthetic physiological parameters,chlorophyll content,meteorological elements and other data during the flowering and filling stages,and analyze the yield structure and grain quality after harvest to explore the changes of photosynthetic physiological characteristics and yield structure of winter wheat under different water conditions,and provide an optimized irrigation plan for areas with limited water supply.The main research work and results are as follows:?1?Under the condition of staged drought stress,the photosynthetic rate of wheat leaves tended to decrease.The net photosynthetic rate of DN,ND and DD at flowering stage decreased by 15.51%,30.42%and 45.08%respectively compared with the control.During the grouting period,DN showed an over-compensation effect.The net photosynthetic rate increased by 9.46%compared to the control,while ND and DD decreased by 16.66%and 28.31%respectively.?2?The staged drought also has a certain effect on the stomatal conductance and transpiration rate of wheat leaves.During the flowering period,the stomatal conductance of DN,ND,and DD decreased by 20.40%,67.76%,and 67.76%,respectively.At the filling stage,the stomatal conductance of DN increased by 8.18%compared to the control,while ND and DD decreased by 73.14%and 38.99%respectively compared to the control.At this time,ND was significantly different from the other three treatments?P<0.05?.The transpiration rates of DN,ND and DD at the flowering stage were reduced by5.96%,41.54%and 48.27%compared with the control.During the filling period,the transpiration rate of DN was 141.84%of the control;ND and DD were reduced by 4.81%and 9.65%respectively.?3?A non-right-angle hyperbolic model was used to fit the photosynthesis-light response curves of wheat flag leaves under various water treatments.The determination coefficient R2 of the four treatments is greater than 0.9.The curve angle of DN??0.986?is the largest,that is,the curve of DN is relatively slow before rising to the light saturation point.The light compensation point LCP of DN is the lowest and the light saturation point LSP is the highest,which are 26.76?mol·m^-2·s^-1 and 450.89?mol·m^-2·s^-1,respectively.The light saturation points of DN,ND,and DD were 16.84%,12.42%,and4.46%higher than the control,respectively.?4?The chlorophyll content of DN,ND and DD in three different stages of drought treatment decreased by 10.90%,15.58%and 24.61%in sequence compared with the control at flowering stage.To the grouting period,the three treatments decreased by7.14%,17.86%and 26.79%year-on-year.The carotenoids content of DN,ND and DD were 89.56%,81.38%and 75.91%of the control at the flowering stage,respectively.By the filling stage,the three treatments were 90.39%,80.78%,and 65.63%of the control.During the two measurement periods,the chlorophyll and carotenoid contents of DD were significantly different from those of the control?P<0.05?.?5?For the DN,ND,and DD after the staged drought stress,the trace elements Fe and Cu in the wheat grains have a larger loss range between 20%-30%.The contents of Zn,Mn,and I have increased significantly;especially the increase of I is between 36%and 45%.Under the DN treatment,the types of elements with reduced mass fractions and the reduced percentages are the least.The content of Zn in DD grains increased by28.87%and passed the extremely significant test?P<0.01?.Except for P under drought stress,the content of a large number of elements such as K,Ca,Na,and Mg increased.The content of a large number of elements in DN grains varied within±20%.ND is basically within±35%.The DD floated greatly,and the mass fraction of its Na element increased by 46%?P<0.01?.?6?The total amino acid content of wheat grains showed a downward trend under different drought treatments.The content of essential amino acids in DN increased by0.92%compared with the control,while ND and DD decreased by 5.11%and 3.13%,respectively.The content of non-essential amino acids in DN,ND and DD decreased by12.72%,20.24%and 30.94%respectively.The protein content of the three treatments was reduced by 3.03%,25.66%,and 23.50%compared with the control.?7?The effects of drought stress on wheat yield in different stages are different.The output of DN?68.12g?is slightly lower than that of CK?77.18g?.But its thousand kernel weight?34.51g?is greater than CK?34.44g?.The harvest index of ND is the lowest among the four kinds of water treatment,only 0.407.Compared with the control,the production of DD was reduced by 42.02%.But its harvest index?0.446?is second only to DN?0.459?.A stepwise regression model was used to construct the relationship between wheat yield and each yield structural element.The resulting stepwise regression equation is y=-5.164x+144.692.Where x is the infertile spikelet rate.The determination coefficient R² of this model is 0.952,and the confidence is greater than95%.?7?The staged drought stress treatment has a certain influence on the microclimate of wheat farmland.The average DN temperature and average relative humidity of the soil surface during the day were reduced by 0.12?and 0.05%compared with the control group.ND increased by 0.02?and 0.28%respectively.DD increased by 0.06?and 1.10%.The average light intensity of the daytime soil surface of DN,ND and DD was 1.84lx,3.01lx and 6.65lx higher than that of the control group,respectively.The average daily temperature of wheat canopy under drought stress decreased.DN decreased by 0.10?,and the other two treatments did not exceed 0.04?.Corresponding DN,ND,and DD canopy daily average relative humidity values have increased,increasing by 0.87%,0.46%,and 1.90%,respectively.The average light intensity of the canopy of these three treatments decreased by 4.44lx,17.85lx,1.84lx in turn.