Shading during the full bolling stage of cotton plants affects their photosynthesis. The study found that shading increases chlorophyll concentration and improves chlorophyll b levels. As shading increases, the maximum photosynthetic rate decreases, but the apparent quantum yield increases. Shading also decreases the efficiency of the photosynthetic process when light intensity is high. Overall, shading can enhance late cotton leaf chlorophyll content, reduce dark respiration, and lower the photosynthetic activity of cotton leaves.