Maintaining higher leaf photosynthesis after heading stage could promote biomass accumulation in rice

Leaf photosynthetic rate changes across the growing season as crop plants age. Most studies of leaf photosynthesis focus on a specific growth stage, leaving the question of which pattern of photosynthetic dynamics maximizes crop productivity unanswered. Here we obtained high-frequency data of canopy leaf CO2 assimilation rate (A) of two elite rice (Oryza sativa) cultivars and 76 inbred lines across the whole growing season. The integrated A value after heading was positively associated with crop growth rate (CGR) from heading to harvest, but that before heading was not. A curve-smoothing analysis of A after heading showed that accumulated A at>80% of its maximum (A(80)) was positively correlated with CGR in analyses of all lines mixed and of lines grouped by genetic background, while the maximum A and accumulated A at <= 80% were less strongly correlated with CGR. We also found a genomic region (similar to 12.2 Mb) that may enhance both A(80) and aboveground biomass at harvest. We propose that maintaining a high A after heading, rather than having high maximum A, is a potential target for enhancing rice biomass accumulation.

Automated summary

Maintaining a high leaf photosynthetic rate after heading is suggested to be a potential target for enhancing rice biomass accumulation, rather than having a high maximum photosynthetic rate. High photosynthetic rate is positively correlated with crop growth rate, especially when it exceeds 80% of the maximum photosynthetic rate.