Determination of water use efficiency of direct seeded upland rice through gravimetric method and associated physiological parameters

Water use efficiency(WUE) and associated physiological parameters were measured in thirty upland advanced breeding lines of rice. WUE showed an inverse trend with mean transpiration rate (r=-0.053) suggesting that stomatal control of WUE among the cultures. However net assimilation rate showed a positive relationship (r=0.79) with WUE indicating possibilities of selecting capacity type cultivars, where mesophyll efficiency would regulate WUE. WUE values of the pot experiment correlated well with those estimated in the field experiment with the same cultures utilizing specific leaf area values at 60 days after sowing. Accordingly the entries B5, B3, B11, B36, B27, B47 and the check Vandana were identified as capacity type cultivars for mining water in order to utilize it efficiently for carbon fixation.