Objective: The growth and development, assimilates accumulation and distribution of organs and its correlation with LAI, LAD and leaf SPAD value of YX-193 and XH-28 during output formative period were studied. Both of them were the improved lines of two major cultivated sea island cotton ( Gossypium barbadense L.) varieties Xinhai 21-Priority system 193, and Xinhai 28 (formerly-code-named TH 45). Method: Indexes such as the growth and development, assimilates accumulation and distribution of Sea Island cotton YX-193 and XH-28 were observed by mulched drip irrigation, using SPAD-502 chlorophyll meter the SPAD values were measured, correlation analysis and regression analysis were used to analyze data. Result: The results showed that stem diameter, leaf area index, photosynthetic potential, leaf area ratio, specific leaf area, relative growth rate, net assimilation rate, maximum LAI, and assimilates accumulation of YX-193 are slightly higher than that of XH-28 except plant height, the most rapid rate of assimilates accumulation is in between 60-90 d after seedling emergence; rules of assimilates distribution rate of different organs are different, their common characteristics are genital organs > vegetative organs > root; assimilates accumulation showed linear correlation with the leaf SPAD value, and meet the quadratic regression model with LAI, LAD. Conclusion: Under the same conditions, the assimilates accumulation of YX-193 are higher than XH-28's during yield formative period; assimilates accumulation of vegetative organs showed a parabolic type, assimilates accumulation of reproductive organs and single plant are close to "S" type. The vegetative organs/total dry weight, leaf dry weight ratio and root to shoot ratio of the two varieties (lines) showed decreasing trend, genital organs/total dry weight showed an increasing trend.
