Abstract: This study showed that the amounts of Bt toxin expressed in transgenic Bt cotton leaves and stems (103.5～134.1 ng·g^-1) were rather higher than those expressed in transgenic Bt cotton roots (44.7～21.2 ng·g^-1), indicating that total amount of soil Bt toxin introduced by transgenic Bt cotton could be decreased through treating its above-ground biomass.In comparing with the amount of Bt toxin expressed in transgenic Bt cotton plant,that expressed in its root exudates was rather lower,showing that the effects of plant Bt toxin on soil ecosystem would be limited if other sources of Bt toxin introduced into soil were controlled.

Key words: Transgeic, Common carp, Environmental factor, Endurance capacity