Effects Of The Substance Bases On Cotton Source-sink Metabolism And Fiber Quality In Wheat-Cotton Double Cropping Systems

Cotton is an important economic crop in China,but because our country has a large population,yet much less land,it makes the contradictions of food crops and cotton competing for arable land increasingly prominent.Double-cropped wheat-cotton cropping systems are the main planting patterns practiced in the Yellow River valley and the Yangtze River valley in China.But different double-cropped wheat-cotton cropping systems,due to the different planting ways and planting time,lead to crop growth in different environments and phenology,which has a significant effect on crop growth,development and production quality.Therefore,how to choose the suitable cropping systems and suitable ripe cotton varieties,as much as possible in order to improve the yield and quality of cotton,is currently an important issue.This test,starting from the source-sink metabolism,through the research on the metabolism and physiological basis of the SBL formation and cotton fiber,aims to reveal the law of cotton yield under different planting patterns of wheat and cotton,and provides theoretical guidance for double-cropped wheat-cotton cropping techniques.The experiment involving four cropping systems,namely monoculture cotton(MC),intercropped cotton(IC),transplanted cotton(TC)and direct-seeded cotton(DC)and two cotton cultivars(Siza 3,mid-later maturing;CCRI 50,early maturing)was conducted in 2012 and 2013 at the cotton experimental station of Nanjing Agricultural University(33°20'N,120°46'E),Dafeng City,Jiangsu Province,China.The objectives of this study were to explore:1,the influence of double-cropped wheat-cotton cropping systems on cotton source sink metabolism,and 2,the influence of double-cropped wheat-cotton cropping systems on the substance metabolism of cotton fiber development and the forming of cotton fiber quality.The main results were as follows:1.The effect on cotton source-sink metabolism under double-cropped wheat-cotton cropping systemsIn the wheat-cotton cropping systems,the SPAD,the Pn and the photosynthesis pigment content of the cotton bolls were reduced more than the monoculture cotton and the development of the SBL of cotton bolls in the DC was delayed.The substance in cotton balls in MC and IC cropping systems transferred faster,and the cellulose and nitrogen metabolism were sped up.However,in the TC and DC cropping systems cotton balls were affected by low temperature at later growth stage,and the boll counterpoint in starch and sucrose output was reduced.In the wheat-cotton cropping systems,cotton bolls,fiber,cotton seed biomass accumulation declined more than that in the monoculture cotton cropping system,with the descending order of MC,IC,TC and DC.In the double-cropped wheat-cotton cropping systems,the Pn of the SBL and the soluble sugar content decreased,which was unfavorable for cotton bolls,fiber and cottonseed biomass accumulation.Soluble sugar/amino acid ratio was lower,causing the fiber biomass descending.Among the cotton cultivars in the double-cropped wheat-cotton cropping systems,the photosynthesis property of Siza 3 was more satisfactory,therefore the boll development was better.Moreover CCRI 50 had greater advantage in the TC and DC cropping systems.2.The effect of double-cropped wheat-cotton cropping systems on the material metabolism of cotton fiber development and its quality formationCompared with the monoculture cotton,the cellulose content under two planting patterns declined but the sucrose increased,while ?-1,3 sugar had little change.The planting patterns of wheat and cotton had a significant influence on cotton fiber quality,in which the greatest effect was on fiber strength and the micronaire,but little effect on fiber length.In contrast with monoculture cotton,the micronaire had a gradual declining in intercropped cotton(IC),transplanted cotton(TC)and direct-seeded cotton(DC)and the micronaire had the greatest reduction in the DC cropping pattern.In the Double-cropped wheat-cotton cropping systems,the reduction of cotton fiber sucrose transformation ratio,the fiber maximum accumulation rate and the rapid accumulation duration lead to fiber strength and the micronaire declining,among which,the quality of direct-seeded cotton(DC)was more remarkable.The planting patterns had a greater influence on the fiber of Siza 3 than on CCRI 50.