Plant photosynthetic rate is affected by stomatal status and internal CO2 carboxylation.
Understanding which process determines photosynthetic rate is essential for developing
strategies for breeding crops with high photosynthetic efficiency. In this study, we identified
different physiological patterns of photosynthetic rate in two different rice populations.
Photosynthetic gas exchange parametersweremeasured during the flowering stage in two rice
populations. Clustering and correlation analyses were performed on the resulting data. Five or
six groups were defined by K-means clustering according to differences in net photosynthetic
rates (Pn). According to differences in stomatal conductance (gs) and carboxylation efficiency
(CE), each group was clustered into three subgroups characterized by physiological patterns
stomatal pattern, carboxylation pattern, and intermediate pattern. Pn was significantly
correlated with gs (r = 0.810) and CE (r = 0.531). Pn was also significantly correlated with gs and
CE in the three physiological patterns. The correlation coefficientswere highest in the stomatal
pattern (0.905 and 0.957) and lowest in the carboxylation pattern (0.825 and 0.859). Higher
correlation coefficients between Pn and gs or CE in the three physiological patterns indicate that
clustering is very important for understanding factors limiting rice photosynthesis.