| Widespread cultivated early maturing upland cottons of different eras in Xinjiang(1990s,2000 s and 2010s)were selected as experimental materials under mulched drip irrigation conditions.Canopy openness,mean foliage title angle and canopy light distribution at different growing stages were measured to reveal the change of cotton canopy structural characteristics.And the changes in chlorophyll content,gas exchange parameters,canopy apparent photosynthetic rate and dry matter accumulation in the progress of varieties replacement and yield improvement were analyzed,Combined with the advancement of machine pick up cotton,we also analyzed the evolution trend of the main plant type characteristics and economic characteristics of varieties from different eras.These provided a theoretical basis for breeding new machine pick up cotton varieties and optimizing cultivation management.1.Changes of Fertility Process and Main Plant Type Characteristics in the Progress of Cotton Varieties Replacement and Yield ImprovementThe results showed that in the progress of cotton varieties replacement and yield improvement improved lint significantly contributed to increased yield and boll number and boll weight also increased.There was different growth period among varieties from different eras.a,variable range of the growth period was 1-10 d for 2 years,while the difference of growth period was mainly due to difference in boll opening stage.From the analysis of plant type characteristics,the plant height increased gradually.The plant height,fruiting node length and ratio of fruit node/fruit branches of modern varieties were greater than those of earlier varieties.The general trend of plant type change was from the compact to the more compact.2.Development of Canopy Structure Characteristics in the Progress of Cotton Varieties ReplacementThe results showed that in the progress of cotton varieties replacement and yield improvement,compared with 1990 s and 2000 s varieties,2010 s varieties had more reasonable canopy openness in the growth period from full bolling stage to boll opening stage and higher light absorption rate In the late growth period,2010 s varieties still maintained the high canopy openness and canopy light absorption rate.Furthermore,2010 s varieties had a higher dry matter accumulation than 1990 s and 2000 s varieties,and there was an increasing trend in the dry matter accumulation of various organs in 2010 s varieties.The change trend was consistent in the leaf inclination angle among different varieties,but leaf inclination angle had a great difference between different varieties.There was negative correlation between leaf inclination angle and leaf size.Therefore,with cotton varieties replacing,the reasonable canopy structure at the middle and later stages of cotton growth can maintain high light absorption rate and photosynthetic matter production,this attributes to increased cotton yield.3.Development of Cotton Photosynthetic Characteristics in the Progress of Cotton Varieties ReplacementThe results showed that in the progress of cotton varieties replacement and yield improvement,canopy photosynthetic rate of 2010 s varieties was significantly higher than that in 1990 s and 2000 s varieties in full boll stage and boll opening stage,there was little difference in canopy respiration rate of varieties from different eras.In addition,leaf photosynthetic rate and chlorophyll content of 2010 s varieties were significantly higher than those of 1990 s and 2000 s varieties,and 2010 s varieties can maintain high leaf area index in the late growth stage,effectively delaying the leaf senescence of upper stage.Therefore,with the development of cotton production and varieties replacement,canopy photosynthetic rate in the middle and late growth stage and chlorophyll content?net photosynthetic rate and leaf area index at the late growth stage can maintain high photosynthetic capacity,and the relatively high photosynthetic biomass production is the physiological basis of high yield.4.Development of Quality Traits and Suitable for Machine Picking Characteristics among Cotton Varieties Replacement ProcessThe results showed that with cotton varieties replacing,plant height and height of first fruit branch node increased gradually,which was suitable to machine picked up.With cotton varieties replacing,the fiber length had a small increase,There was no above 31 mm and 25 mm to 27 mm fiber.Specific strength was significantly improved and Micronaire value increased gradually.The Micronaire value of 1990 s varieties was the best,but the fiber length and specific strength were low.The Micronaire value of 2000 s varieties was better,but the fiber length and specific strength were also relatively low.The fiber length and specific strength of 2010 s varieties were significantly improved,but the Micronaire value was relatively large.Therefore,with the development of cotton production,it was the key for selecting the high yield and good quality varieties suitable for machine picked up to promote the rapid development of cotton industry in Xinjiang. |
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