Effects Of Wheat-cotton Cropping Systems On Physiological Mechanism Of Cottonseed Yield And Guality

Wheat-cotton double cropping system was practiced at a large scale in the Yellow River valley and the Yangtze River valley in China.It effectively improved the multiple crop index and economic benefit of the land,and remitted the land contradiction between grain and cotton.With the growing demand of cottonseed,it had an important use in various fields as the mean byproduct of cotton production.By studying the effects of cropping system on the physiological basis of cottonseed yield and quality,we can provide a theoretical basis for improving the yield and quality of cottonseed based on the stability of cotton production in wheat-cotton regions of China.Field experiments were conducted in 2012 and 2013 at the cotton experimental station of Dafeng City,Jiangsu Province,China.Two cotton cultivars,Siza 3(Mid-late maturity)and CCRI 50(Early maturity)were used in the experiment.Field experiments were composed of four cropping systems with monoculture cotton(MC)as contrast,and three wheat-cotton double cropping systems were intercropped cotton(IC),transplanted cotton(TC)and direct-seeded cotton(DC).The effects of Wheat-cotton double cropping system on growth,yield and quality,embryo sucrose metabolism,fat and protein metabolism of cottonseed were studied.The main results were as follows:1.The cottonseed yield was decreased in wheat-cotton double cropping systemWheat-cotton double cropping system significantly affected the cottonseed growth,the growth period of double-cropped cotton was delayed more than MC,and DC was significantly delayed 14-20 d.The cottonseed volume of double-cropped cotton was declined more than MC,DC was significantly decreased by 17.9%-19.0%.Otherwise,wheat-cotton double cropping system significantly affected the biomass dynamic accumulation and distribution of cottonseed.Cottonseed embryo percentage of IC and TC were increased than MC,but DC was markedly reduced.In addition,the cottonseed and embryo yield of double-cropped cotton were lower than MC,mainly on account of the decreased boll number.The embryo fat content of double-cropped cotton was also lower than MC;the protein and Amino acid content of IC,TC were higher than MC,but those of DC were lower.Moreover,variety comparison showed that the SIZA 3 had the advantage of cottonseed yield,but CCRI 50 had the superiority of cottonseed quality.2.The content of soluble sugar and sucrose of cottonseed were decreased in wheat-cotton double cropping systemWheat-cotton double cropping system significantly affected the accumulation and key enzyme activities of sucrose metabolism in cotton embryo.The cotton embryo soluble sugar and sucrose content of double-cropped cotton were lower than that of MC,with the descending order of IC,TC and DC.Besides,the cotton embryo starch content of DC was higher than that of MC,however,IC and TC were lower than that of MC.And the key enzymes were markedly influenced by the wheat-cotton double cropping system.The double-cropped cotton had lower sucrose phosphate synthase(SPS)but higher acid and alkaline invertase(Inv)activities compared with MC,so that it was against the accumulation of soluble sugar and sucrose.Furthermore,the activities of sucrose synthetase(SuSy)of IC and TC were lower than those of MC,however,DC was significantly increased with the high starch content.Correlation analysis showed that the starch content of cotton embryo was significantly and positively correlated with SuSy,on contrast.The SPS activity was significantly and positively correlated with soluble sugar and sucrose of cotton embryo,the acid and alkaline Inv were opposite.In summary,double cropped wheat-cotton was adverse to increasing the content of soluble sugar and sucrose,but DC was conducive to the enhancement of starch content.3.The content of fat in cotton embryo was decreased in wheat-cotton double cropping system but IC and TC impoved the protein contentWheat-cotton double cropping system significantly affected the accumulation of fat and protein.And its effect of eigen values especially the speedy accumulation of fat and protein was the important cause leading to the differences of cottonseed quality.The cotton embryo fat content of the double-cropped cotton was lower than that of MC,with the descending order of IC,TC and DC.Besides,the cotton embryo protein content of IC,TC were higher than that of MC,however,DC was lower than that of MC.Compared with MC,the double-cropped cotton had lower phosphatidate phosphatase(PPase)and glucose-6-phosphate dehydrogenase(G6PDH)but higher phosphoenolpyruvate carboxylase(PEPC)activities with the limit to increasing the fat content of cotton embryo.Furthermore,the activities of glutamine synthetase(GS)and glutamate synthase(GOGAT)of IC and TC were higher than those of MC,however,those of DC were lower,so that the protein of cotton embryo was increased.Moreover,the contents of cotton embryo fat and protein were higher in CCRI 50 than in Siza 3.In summary,intercropped cotton with mid-maturity cotton cultivars should be utilized to increase the quality of cottonseed on the basis of the stable cotton yield and quality in wheat-cotton regions of China.