Temperature response of bundle-sheath conductance in maize leaves
A small bundle-sheath conductance (gbs) is essential for the C4 CO2-concentrating mechanism to suppress photorespiration effectively. To predict the productivity of C4 crops accurately under global warming, it is necessary to examine whether and how gbs responds to temperature. We investigated the temperature response of gbs in maize by fitting a C4 photosynthesis model to combined gas exchange and chlorophyll fluorescence measurements of irradiance and CO2 response curves at 21% and 2% O2 within the range of 13.5–39 °C. The analysis was based on reported kinetic constants of C4 Rubisco and phosphoenolpyruvate carboxylase and temperature responses of C3 mesophyll conductance (gm). The estimates of gbs varied greatly with leaf temperature. The temperature response of gbs was well described by the peaked Arrhenius equation, with the optimum temperature being ~34 °C. The assumed temperature responses of gm had only a slight impact on the temperature response of gbs. In contrast, using extreme values of some enzyme kinetic constants changed the shape of the response, from the peaked optimum response to the non-peaked Arrhenius pattern. Further studies are needed to confirm such an Arrhenius response pattern from independent measurement techniques and to assess whether it is common across C4 species.
Xinyou Yin, Peter E.L. van der Putten, Steven M. Driever and Paul C. Struik (2016) Journal of Experimental Botany (online first 11 March 2016)
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