Preliminary Study On Photosynthesis Characteristics And Cluster Analysis Of Cotton Varieties

The study on Photosynthetic Characteristics (net photosynthetic rate and chlorophyll fluorescence parameters) of 65 cotton Varieties were measured by the LI一6400 Portable Photosynthesis System Under-mulch-drip irrigation Conditions, and classified these cotton Varieties preliminary. The main conclusions are as follows:1. The change of net photosynthesis and chlorophyll fluorescence parameters of different genotypes cotton leaves in main growing stages.The net photosynthetic rate comes to the highest from full squaring stage to blooming stage , a slight decline after the early blooming stage and rapid decline in bolling stage; The value of Fo and Fm have rising from full squaring stage to bolling stage; The value of Fv/Fm and Fv/Fo from full squaring stage to the full blooming stage enhanced gradually and then decreased; The value of qP is decreased from full squaring stage to blooming stage and then enhanced, the highest value comes to the full squaring stage; The value of qN and NPQ are performance decline-rise-decline trend from full squaring stage to bolling stage.2. Correlation analysis between photochemical parameters and the main economic characteristics in main growing stages.The Correlation coefficient between Net photosynthetic rate and chlorophyll fluorescence parameters in full squaring stage is negative but positive in blooming stage ,the full blooming stage and bolling stage, The Correlation coefficient of Pn with Fm, Fv/Fm, Fv/Fo, qN, NPQ relatively high in main growing stages, Fm, qN particularly evident; Correlation analysis of net photosynthetic rate and chlorophyll fluorescence parameters with the main economic characteristics show that: The correlation coefficient between Pn and fiber length is relatively higher; Fo with yields is relatively higher, Fm with lint percentage is relatively higher; Fv/Fm, qP with Boll number are relatively higher; Fv/Fo with fiber intensity is relatively higher; qN, NPQ with micronaire are relatively higher.3. Using Principal component analysis and cluster analysis to divide cotton varieties.Principal component analysis and cluster analysis were performed for 16 traits of 65 cotton genotypes. The results indicated that the contribution of the first seven principal components to total variation of population studied accounts for over 81.898%. According to the result of principal component analysis, seven principal components as a result of the new variables, through cluster analysis, 65 cotton Varieties were divided into four clusters by hierarchical clustering method. The largest cluster is the type with higher optimal photochemical efficiency of PSII, Photochemical quenching coefficient and Photosynthesis capacity, middle yields, greater fiber quality and lower based fluorescence.