Central Rice Research Institute, Cuttack
The multiple measurements on diurnal changes in photosynthetic rate (Pn), stomatal conductance (Cs), leaf temperature (Lt) and photosynthetically active photo flux density (Qu) on intact flag leaf were conducted at hourly intervals (8 to 17 hrs) in six early elite rice cultivars at flowering stage with a portable photosynthesis system (LI-6000). The maximum values of Pn and Cs were recorded at 10 hrs when the Qu was 1200µE m−2s−1 and Lt of less than 35°C. Pn and Cs decreased from 10 to 14 hrs followed by slight increase at 15 hrs and a steep decline till 17 hrs. The mean Pn among the varieties was in the decreasing order Ptb 10, Kalinga-II, Co 41, Adt 32, Ratna and Swarnaprabha.
