Temperature responses of photosynthesis and leaf hydraulic conductance in rice and wheat

Studies on the temperature ( T ) responses of photosynthesis and leaf hydraulic conductance ( K leaf ) are important to plant gas exchange. In this study, the temperature responses of photosynthesis and K leaf were studied in Shanyou 63 ( Oryza sativa ) and Yannong 19 ( Triticum aestivum ). Leaf water potential (Ψ leaf ) was insensitive to T in Shanyou 63, while it significantly decreased with T in Yannong 19. The differential Ψ leaf  −  T relationship partially accounted for the differing g m – T relationships, where g m was less sensitive to T in Yannong 19 than in Shanyou 63. With different g m – T and Ψ leaf – T relationships, the temperature responses of photosynthetic limitations were surprisingly similar between the two lines, and the photosynthetic rate was highly correlated with g m . With the increasing T , K leaf increased in Shanyou 63 while it decreased in Yannong 19. The different K leaf – T relationships were related to different Ψ leaf – T relationships. When excluding the effects of water viscosity and Ψ leaf , K leaf was insensitive to T in both lines. g m and K leaf were generally not coordinated across different temperatures. This study highlights the importance of Ψ leaf on leaf carbon and water exchanges, and the mechanisms for the g m – T and K leaf – T relationships were discussed.