Abstract: The physiological mechanism of over-compensation in cotton plants, Gossypium hirsutum, for simulated infestation of the cotton bollworm, Helicoverpa armigera, on early squares was studied. Removal of 8 early squares by hand from each plant gave 13.4% more bolls than the control, and the increase in the bolls on the 6th and higher fruiting branches of treated plants contributed more to the increase of total bolls. Physiological determination showed that soluble sugar and starch contents in treated cotton leaves increased, while content of total free amino acids decreased. Increase in total leaf area (8.5%-28.1%) and photosynthetic activity (3.6%-6.7%) suggested they could be important reasons for the overcompensation observed in the treated plants, which resulted in higher productivity.

Key words: Gossypium hirsutum, Helicoverpa armigera, simulated infestation, overcompensation, physiological mechanism