Effects of Planting Density and Row Spacing Configuration on Sugar Accumulation and Lodging Performance of Wheat Stem Under Rainfall Harvesting Planting Mode
[Objective]The aim of this study was to analyze the effects of different planting densities and row spacing configurations on stem carbohydrate accumulation and lodging resistance of wheat under ridge-furrow rainfall harvesting planting mode,and to clarify the reasonable density and row spacing of wheat under ridge-furrow rainfall harvesting planting mode,so as to provide a theoretical basis for further stabilizing and increasing wheat yield.[Method]Xinong 979 was the main wheat cultivar in the arid area of north China,which was used as the experimental material.In 2019-2021,two planting densities(low density:1.8 million plants per hm2;high density:2.25 million plants per hm2)and two row spacing(equal row spacing:20 cm;non-equal spacing:12.5 cm:35 cm:12.5 cm)treatments were set in the rainfall harvesting planting mode.The effects of different densities and row spacing on photosynthetic rate of middle and lower leaves in wheat plants,content of stem non-structural carbohydrates and structural carbohydrates,stem breaking moment and lodging index,and grain yield were analyzed.[Result]The net photosynthetic rate(Pn)of the middle and lower leaves(the third leaf,the fourth leaf and the fifth leaf)in wheat plants,the content of non-structural carbohydrates(glucose,fructose,sucrose)and structural carbohydrates(hemicellulose,cellulose)in the second internode at the base of stem,and the stem breaking moment were significantly decreased with the increase of planting density in the rainfall harvesting planting mode,but the stem lodging index increased significantly.However,under high-density planting condition,non-equal row spacing treatment could significantly change all plant indexes.Compared with high planting density+equal spacing treatment,the Pn of the third leaf,the fourth leaf and the fifth leaf in plants increased significantly,with increases of 7.7％-16.5％,5.3％-37.7％and 11.9％-24.9％,respectively;the content of glucose,fructose and sucrose in stems increased by 9.8％-15.0％,8.8％-27.4％and 8.2％-41.1％,respectively;the content of hemicellulose and cellulose increased by 4.5％-19.8％,5.9％-31.2％,respectively;the stem breaking moment increased by 4.8％-17.3％,the stem lodging index decreased by 10.9％-25.9％,while wheat yield was significantly increased by 13.5％-15.2％.Correlation analysis showed that,the content of glucose,fructose and sucrose in the basal internode of wheat stem were positively correlated with the content of hemicellulose and cellulose.Non-structural carbohydrates and structural carbohydrates in wheat stem were positively correlated with Pn of middle and lower leaves as well as stem breaking moment,however,they were negatively correlated with lodging index.[Conclusion]Under the rainfall harvesting planting mode,adjusting population spatial distribution by non-equal row spacing could effectively increase photosynthetic rate of middle and lower leaves of wheat plants,promote the synthesis and accumulation of sugar substances in stems,and enhance the lodging resistance of wheat stem,furthermore,reduce the lodging incidence of wheat and improve grain yield.
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