Using fluorescence microscopy combined with pharmacological methods,we studied the effects of exogenous CO and NO on the DNA degradation and survival rate of aleurone cells in germinating rice (Oryza sativa L.) seeds and its aleurone layers under drought stress.The results showed:(1)The treatment of drought stress promoted the aleurone cells death,and the death of aleurone cells near the embryo occurred earlier than those in the far embryo.(2)Exogenous CO and NO donors alleviated the degradation of DNA in rice aleurone cells under drought stress,and delaying the process of cell death.Meanwhile,effects of CO and NO were reversed by CO specific inhibitor and NO scavenger,and shortening the process of cell death.(3)Exogenous CO and NO donor promoted the germination of rice seeds under drought stress.However,CO specific inhibitor and NO scavengers inhibited the germination of rice seed under drought stress.(4)The experimental results also revealed that CO mediated by NO regulated the aleurone cells death and germination of rice seeds under drought stress.