Rice (Oryza sativa L.) hydraulic conductivity links to leaf venation architecture under well-watered condition rather than PEG-induced water deficit

Higher plant hydraulic conductivity (Kplant) is vital for plant growth, especially under PEG-induced water deficit stress (PEG-IWDS). Leaf venation architecture is a key determinant of leaf hydraulic conductivity (Kleaf) and Kleaf is a major component of Kplant across different plant species. However, there is little information about (1) varietal difference in leaf vein development in cereal crops, such as rice plants; (2) the effects of PEG-IWDS on leaf vein development; (3) the coordination between leaf venation architecture and Kplant as well as Kleaf under PEG-IWDS. In the present study, widely cultivated eight rice cultivars were grown hydroponically under well-watered condition (WWC) and PEG-IWDS, simulated by adding 15 % (w/v) PEG6000. Leaf venation architecture, including total longitudinal leaf vein number, leaf vein numbers per unit width (LVNW), vein thickness and leaf mass per area, as well as Kplant and Kleaf were measured to address above-mentioned questions. The results showed that leaf venation architecture exhibited significant varietal differences and PEG-IWDS significantly increased LVNW while decreased vein thickness. PEG-IWDS suppressed both Kplant and Kleaf but the decrease was much higher in Kplant than Kleaf. There was a significant and positive correlation observed between LVNW and Kleaf under both WWC and PEG-IWDS but the correlation between LVNW and Kplant was only significant under WWC. Kleaf was significantly and positively correlated with Kplant under WWC but not under PEG-IWDS. It is concluded that Kleaf is a major determinant for Kplant under WWC but not under PEG-IWDS; therefore, breeding or selecting rice cultivars with high LVNW can improve shoot water supplement under WWC but not under PEG-IWDS condition.