Large leaf modulus of elasticity is associated with the distinct midday reduction of photosynthesis in rice (Oryza sativa L.): a comparison with green gram (Vigna radiata (L.) R.Wilczek)

ABSTRACT A distinct midday to afternoon (midday) reduction of leaf photosynthetic rate (A n) occurred in rice, even under well-irrigated conditions on a clear day, but not in green gram. No significant differences between species in leaf water potential (Ψleaf) or plant resistance to water transport during daytime were found. From the pressure–volume curves, it was revealed that rice leaves had a larger bulk modulus of elasticity (ε), and their turgor pressure (TP) decreased more as Ψleaf declined than of green gram leaves. The TP of rice leaves was estimated to be lower in the midday than that of green gram. We attribute the distinct midday reduction of A n in rice to the larger ε of rice than that of green gram. Graphical abstract