Abstract: The differences of root physiological characteristics within hybrid rice varieties were studied in the field experiment. It was shown that the change trend of root physiological indexes within rice variety was consistent， but the contents of most root physiological indexes varied significantly except the root activity during heading stage. Root activity， bleeding intensity， contents of amino acid and soluble sugar in rice cv. Gangyou725 were higher than those in other rice varieties in most of the growth period. The contents of protein and soluble sugar were higher in rice cv. Ⅱyou725 at the heading stage. All physiological indexes were the lowest in the control variety. Correlation analysis indicated that there was a positive correlation among all root physiological indexes and yield for most of the growth period， which indicated the feasibility of increasing rice yield by improving root physiological properties.

Key words: hybrid rice, root, physiological characteristics, bleeding intensity