Effects of exogenous cytokinin on photosynthesis, senescence, and yield performance of inferior rice tillers grown under different nitrogen regimes

Inferior tillers contribute negligibly to rice grain yields as their late occurrence or prematurity curtails growth. However, 6-benzylaminopurine (6-BA, a synthetic cytokinin) can delay tiller senescence. Our results indicate that foliar application of 6-BA enhanced the distribution and allocation of light energy for the photochemical reactions of PSII, under appropriate N supply. The percentage of thermal energy dissipation also decreased following the application of 6-BA as a consequence of the reduced risk of chloroplast oxidative damage through excess excitations. Moreover, leaf peroxidase, catalase, and ascorbate peroxidase activities were augmented by adding 6-BA, which significantly inhibited the accumulation of malondialdehyde and H2O2. The application of 6-BA increased the grain numbers of the inferior tillers and further enhanced tiller yields under 82.5 and 165 kg(N) ha-1 supply. The effect of 6-BA was negligible for the untreated or excessive N-treated plants.