High Leaf Vein Density Promotes Leaf Gas Exchange by Enhancing Leaf Hydraulic Conductance in Oryza sativa L. Plants

Six cultivated rice genotypes showing different stomatal conductance (g(s)) values were used to investigate the influence of leaf vein traits on leaf gas exchange and leaf hydraulics. The results showed that g(s) was the main determinant of the varietal difference in the net photosynthetic rate (P(N)), whereas the area-based leaf nitrogen content (N(area)) and mesophyll conductance (g(m)) were not main factors. g(s) and P(N) were both positively correlated with leaf hydraulic conductance (K(leaf)). A high density of leaf veins (vein length per leaf area, VLA), especially minor leaf veins (VLA(minor)), was of benefit for improving the K(leaf). The proportion of the minor leaf vein length to the total leaf vein length did not impact the leaf hydraulics or leaf gas exchange. Overall, these findings suggested that a high density of leaf veins, especially minor leaf veins, enhances K(leaf) and promotes g(s) and P(N) in cultivated rice genotypes and a high VLA can be regarded as a high photosynthetic capacity trait in rice plants.