Abstract: A study on Cd phytotoxicity to hybrid rice and conventional rice at different growth stages was conducted using water cultures.The results showed that the principal toxic effects of Cd on rice before ear initiation were the reduction of the photosynthetic production,with as typical features:the hardening of roots,yellowed leaves,and emaciated vegetation.In the stages from ear initiation to heading,the main phytotoxicity of Cd was inhibition of the differentiation and development of the reproductive organs which lead to luxuriantly tillering and sterility of caryopses.After the heading stage, the main effects of Cd toxicity were that the transport and redistribution of nutrients in vivo were disturbed.Typical features were the appearance of a large numher of later tilleis and pooly mature rice.The largest influence of Cd on rice nutrition appeared to be the reduction of the physiological availability of nutrient elements(N,P,K) absorbed by rice plants.and the increased accumulation of these elements in rice leaves and straws at the ripening stage.As to the effect of rice yield(brown rice),the most sensitive stage for both rice genes to Cd toxicity was from ear initiation to heading. Hybrid rice was more sensitive than conventional rice to Cd pollution. 

Key words: hybrid rice, conventional rice, Cd, phytotoxicity, water culture