| Xinjiang is located in the northwest arid areas,which is the typical oasis irrigation agriculture in our country,92.4%of arable land is irrigated farmland.However,the average annual precipitation of Xinjiang Uyghur Autonomous Region is only 100-200 mm,which agricultural production is totally dependent on irrigation.In recent years,Xinjiang Uyghur Autonomous Region of China has seen the successful adoption of drip irrigation into wheat production to cope with the extreme shortage of water resource,and water imbalance in field due to dramatic high evaporation vs very little precipitation.However,the input is high since one drip tube serves only four rows of wheat plants in the current irrigation pattern.Here,performances of irrigation patterns differing in ratios of drip tube to spring wheat plant rows were compared in a field experiment in the experimental years of 2014 and 2015.Three ratios were set as one tube serves four(TR4,as control),five(TR5)and six(TR6)rows of plants(row spacing of 15 cm).Variations in grain yield,quality and water use efficiency(WUE)were observed within different wheat rows(R1,R2 and R3 indicated 1st,2nd and 3rd row adjacent to the drip tube,respectively).1.The interrow variation between three drip irrigation patterns was increased with the increase of lateral spacing.With increasing TR ratio,grain yield,ear number,grain number per ear,1000-kernel weight declined in all rows.This resulted in lowered grain yield and WUE while increased evapotranspiration in TR6 and TR5 in comparison to TR4.It is very interesting that the percentage of decrement in grain yield in R3 and R2 in relation to R1 was much lower than the decrement of received irrigation water(RIW).This mechanism should be helpful for developing new drip irrigation wheat patterns with higher TR ratio under conditions of reduced RIW.2.Broadening the lateral spacing was beneficial to increase the quality of grain flour,but also increased the wheat interrow variation of quality.The influence of drip irrigation on the variation of the quality of wheat is mainly caused by the difference of quality in the pearling fraction(P)2 to P6.Compared with the TR4,TR5 and TR6 improved the grain flour glutenin content and glutenin/gliadin;at the same time,the total protein content of TR5 was higher than the TR6,and with lower C.V among wheat rows.This indicated that TR5 is more conducive to improving the processing quality of wheat flour.TR5 and TR6 had the higher GMP content,wet(dry)gluten content,SDS-sedimentation value,dough development time than TR4,but the C.V among wheat rows in TR6 was higher than TR5 which was disadvantageous to the protein processing quality.At the same time,wheat grain had the the lowest amylose/amylopectin ratio in the TR5,which was beneficial to the improvement of wheat grain starch processing products.Therefore,under the three drip irrigation patterns,TR5 is more favorable for grain quality stability of spring wheat in Xinjiang with lower C.V among wheat rows than TR6.The interrow variation in wheat grain protein content mainly concentrated in P2 to P6.Wheat glutenin interrow differences are mainly in the P2 and P7 layer,layer of grain in different grain glutenin/gliadin ratio is R1 and R2 were significantly higher than that of R3,R1 and R2 were insignificant difference,because protein processing quality level is depend on the flour glutenin content and glutenin/gliadin ratio.The interrow differences of GMP content in different layers were mainly in P2 and P4.Dry and wet gluten content directly affects the processing quality of wheat flour,dry and wet gluten content have larger interrow variation in P2 to P4 layers.The interrow variation of sedimentation value is larger in P3 to P5 layers.interrow quality variability is mainly caused by P2 and P5 layer quality variation through the analysis of grain pearling fraction quality.3.With the increase of the lateral spacing in the three patterns,the metabolic capacity of carbohydrate-nitrogen in source and sink of spring wheat was decreased and the interrow variation increased.The flag leaf chlorophyll content,nitrogen content,soluble protein content,soluble sugar and sucrose content of the wheat rows in The TR4 were the higher than TR5 and TR6.The flag leaf soluble sugar and sucrose content of TR5 were insignificantly different with TR4 at filling stage,while TR6 was significantly lower than that of TR4 and TR5.Because of the sugar and nitrogen accumulation of flag leaf were highly decreased,the interrow variation increased with the wider lateral spacing.The sucrose-phosphate synthase(SPS),nitrate reductase(NR)and glutamine synthetase(GS)activity of R1 in three drip irrigation partners showed higher than R2 and then R3.The C.V of wheat rows increased with increasing TR ratio,whilst the C.V was higher in middle filling stage than late filling stage.The drought priming in the early growing stage of wheat most probably relieve the drought stress in the late growing stage,and then lessened the interrow variation of grain yield.Higher nitrogen metabolism enzyme activity in favour of the nitrogen assimilation which was translated to grain and accumulated.Higher interrow variation of nitrogen metabolism enzyme activity most probably induced the grain nitrogen accumulation and quality variation among the wheat rows.The activity of sucrose synthase(SS)of TR4 was higher than TR5 and TR6.The SS activity of R3 in TR6 was significantly lower than R2 and R3,which was unfavorable to the synthesis of starch,resulting in a big difference in grain weight between rows.The activity of soluble starch synthase(SSS)and granule-bound starch sy nthase(GBSS)in TR4 and TR5 were higher than TR6,whilst The SSS and GBSS activity of distant rows were significantly lower than the adjacent rows in TR6,which were unfavorable to the synthesis of starch.Starch is the most important part of the grain dry matter,and the starch metabolism enzyme activity directly influence the grain starch content.The starch metabolism enzyme activity of distant wheat row in TR5 and TR6 decreased much which induced the grain starch highly reduced,and then probably result in bigger interrow variation with wider drip lateral spacing.Moderate drought stresses have been reported here,the absolute amount of the redistributed dry matter(DMR)of R2 and R3 was lower than R1.However,the rate of the DMR and the contribution of DMR to grain yield was much higher in R2 and R3 than in R1(Table 3).Here,the rate of DMR(DMR-R)of R3 was higher than R2 and R1,while the contribution(DMR-C)of R3 was higher than R2 and R1.This was related to the less decrease in leaf area index and relative water content in flag leaf of plants in R3 than R1,and the compensation of the enhanced contribution of the redistributed dry matter stored in vegetative organs before anthesis into grains after anthesis in plants of R3 and R2 rows.Thus,the improved redistribution of the pre-anthesis synthesized dry matter to grain and the enhanced HI were concluded to also contribute to the less grain yield loss of the distant rows in the present study.Drought-primed(an earlier moderate drought event)plants in vegetative organs essentially improved the tolerance to post-anthesis drought stress,and in favour of plant water status keep a higher level than the non-primed plants in wheat.4.The variation of grain yield among different cultivars due to the difference in the dry weight and activity of root and leaf area in one tube servers six wheat rows drip irrigation pattern,which were different among the spring wheat cultivars.The interrow difference of grain yield of xinchun 40 and xinchun 44 cultures were smaller than other cultures,whilst with higher grain yield,leaf area and xylem sap content,which had a significant relationship with the yield.The interrow difference of grain yield of xinchun 11 and xinchun 22 cultures were higher with lower grain yield,leaf area and xylem sap content.The higher root dry weight is beneficial to the absorption of soil water and fertilizer by wheat,which is beneficial to the formation of wheat yield.The interrow of root dry weight difference is larger,which caused the higher interrow variation in grain yield among different wheat rows.It is of positive significance to select the cultivars with higher yield and less interrow difference in the larger lateral spacing drip irrigation pattern. |
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