Conditional variations in temperature response of photosynthesis, mesophyll and stomata! control of water use in rice and winter wheat

Environmental responses of photosynthesis and CO2 diffusive conductance as fundamental information for photosynthesis-transpiration coupled model have been increasingly concerned while are still research areas with unanswered questions in cereal crops. Photosynthesis (A), light utilization efficiency (alpha), mesophyll conductance (g(m)) and stomatal coefficient (g(fac)) in temperate rice and winter wheat were investigated. There were no seasonal trend, no inter- and intra-species differences in relative temperature responses (activation energy Delta H-a) of V-cmax or J(max). A phenomenon that grain-filling plants generally decreased g(m) and had a lower Q(10) as compared to that at early growth stage existed, particularly in rice. Analyses of environmental influences indicated that optimal temperatures (T-opt) in V-cmax/J(max) depended on the prevailing temperature environment. Although prevailing temperature dependence in T-opt of g(m) was not as profound as that of V-cmax or J(max), Topt of g(m) in winter wheat was significantly lower than rice. Temperature response of R-dark in all sampled leaves shared a common trajectory. alpha were almost invariant, while, high sensitivity to soil desiccation was observed. g(fac) in sunlit leaves was conservative during wet soil conditions. Shaded leaves with lower N-a had higher g(fac), resulting in a negative correlation between N-a and g(fac) in canopy profiles. g(fac) was susceptible to fluctuations in soil water potential (psi(s)), rapidly declined at a threshold of top-layer psi(s), approx. -0.1 MPa. Numerical analyses regarding g(m)/V-cmax/J(max) effects on photosynthetic performance in rice and between rice and winter wheat documented that in context of climate change, consider growth environment-induced differences in temperature responses of photosynthetic parameters among cereal crops is indispensable to better predict interactions among soil-plant-atmosphere consortium. (C) 2016 Elsevier B.V. All rights reserved.