Functional consequences of light intensity on soybean leaf hydraulic conductance: Coordinated variations in leaf venation architecture and mesophyll structure

Leaf hydraulic conductance (Kleaf) is a critical determinant of photosynthesis. Prior research has assessed the influence of light intensity on Kleaf by affecting leaf veins. However, whether the mesophyll structure is asso-ciated with leaf hydraulic acclimation to different light intensities remains unclear. We investigated the re-sponses of leaf gas exchange and Kleaf to different growth light intensities and checked for the correlation of Kleaf with leaf structural traits in soybean. Low light significantly reduced Kleaf, but Kleaf and stomatal conductance remain coordinated. Low light decreased the stomatal density to match the balance between in water supply and carbon gain capacity. The decline in Kleaf under low growth light condition was partly due to for the reduction of the water movement through leaf veins because of reduced leaf vein thickness and density and xylem conduit size. In addition, low light reduces the mesophyll cell-to-cell connectivity and increased the volume fraction of intercellular air space. As a result, the area available for liquid-phase flow decreases, and subsequently decreased Kleaf. The present study highlights the coordination role between leaf venation architecture and mesophyll structure influencing Kleaf in response to light intensity.