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

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