Abstract: The effect of shading during symbiotic stage of inter cropped cotton and wheat on cotton yield and its quality formation was examined by simulated shading at the seedling stage of cotton.The results showed that the effect of shading on the cotton boll formation depended upon the position of frurting branch and fruiting bud.For the bolls at low(1～3 fruiting branches) and middle(4～6 fruitng branches) parts and the inside bolls(1～2 fruiting buds)on upper(7～9 fruiting branches)fruiting branch,shading favored boll formation, but for the outside bolls(≥3 fruiting buds),especially at the top fruiting branch position, shading was unfavorable to boll formation.The effect of shading on the weight of individual boll also depended upon the position of fruiting branch and fruiting bud,but shading did not affect the mean boll weight per plant. For seed cotton yield per plant,the inside boll yield of shaded low and middle fruiting branches was higher than the control, but that of the upper and top fruiting branches was just contrary,the yield of outside bolls of all branches was lower than the control.For the distribution of the inside and outside bolls, shaded cotton was 1:0.36,versus 1:0.58 for the control.For the yield distribution,shaded cotton was 1:0.42,versus 1:0.72 for the control.The effect of shading on the cotton fiber and seed quality was mainly restricted on the bolls of top fruiting branches and the outside bolls of upper fruiting branches.The results also showed that different cotton varieties were different in their shade tolerance,according to comprehensive analysis of the yield and quality formation, and the shade tolerance of variety Zh9418 was stronger than that of Zh19 and CAZ.

Key words: Seedling stage, Shading, Cotton, Yield and quality formation