Colored cotton has naturally pigmented fibers.The mechanism of pigmentation in cotton fiber is not well documented.This experiment was conducted to study the effects of respiratory chain inhibitors,i.e.,rotenone and thiourea,on pigmentation and fiber development in colored cotton.After 1 d post-anthesis,ovaries were harvested and developing ovules were cultured on the liquid medium containing different concentrations of rotenone and thiourea for 30 d.The results demonstrate that both respiratory inhibitors reduced fiber length and ovule development under ovule culture conditions,and the inhibition efficiency of rotenone was much higher than that of thiourea.Rotenone and thiourea also showed significant effects on fiber pigment (color) development in colored cotton.In green cotton fiber,rotenone advanced fiber pigment development by 7 d at 200 μmol/L,while thiourea inhibited fiber pigmentation at all treatment levels (400,600,800,1000,and 2000 μmol/L).Both respiratory inhibitors,however,had no significant effects on pigmentation of brown cotton fibers.The activities of cytochrome c oxidase (COX) and polyphenol oxidase (PPO) decreased significantly with increasing levels of both respiratory inhibitors.It is suggested that both respiratory inhibitors have important roles in deciphering the mechanism of pigmentation and fiber development in colored cotton. Colored cotton has naturally pigmented fibers. The mechanism of pigmentation in cotton fiber is not well documented. This experiment was conducted to study the effects of respiratory chain inhibitors, ie, rotenone and thiourea, on pigmentation and fiber development in colored cotton. After 1 d post-anthesis, ovaries were harvested and developing ovules were cultured on the liquid medium containing different concentrations of rotenone and thiourea for 30 d. the results demonstrate that both both respiratory inhibitors reduced fiber length and ovule development under ovule culture conditions, and the inhibition efficiency of Rotenone was much higher than that of thiourea. Rotenone and thiourea also showed significant effects on fiber pigment (color) development in colored cotton. In green cotton fiber, rotenone advanced fiber pigment development by 7 d at 200 μmol / L, while thiourea inhibited fiber pigmentation at all treatment levels (400, 600, 800, 1000, and 2000 μmol / L) .Both respiratory inhibitors, howev er, had no significant effects on pigmentation of brown cotton fibers. The activities of cytochrome c oxidase (COX) and polyphenol oxidase (PPO) decreased significantly with increasing levels of both respiratory inhibitors. It is suggested that both both respiratory inhibitors have important roles in deciphering the mechanism of pigmentation and fiber development in colored cotton.