The photosynthetic efficiency of some elite rice hybrids and restorers

At the vegetative growth stage (40 d), the mean photosynthetic rate (P-N) and canopy photosynthesis (P-N x LAI) in F-1 hybrids and their parents were similar, whereas the maintenance respiration rate (R-M) was considerably higher and P-N/R-M lower in the F-1 hybrids than in the parents. Yet at the flowering stage, the hybrids showed higher P-N and P-N x LAI values, while R-M and P-N/R-M were similar in both. A specific F-1 hybrid like IR 62829AxVajram showed high readings in P-N, P-N/R-M, and P-N x LAI at the flowering stage, while IR 62829AxSwarna followed by IR 62829AxVajram had high values 40 d after planting. The parents Swarna and Vajram, although moderate in P-N, had the highest P-N x LAI at the flowering stage due to a greater LAI.