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