Temperature dependences of carbon assimilation processes in four dominant species from mountain grassland ecosystem

Abstract

Temperature responses of carbon assimilation processes were studied in four dominant species from mountain grassland ecosystem, i.e. Holcus mollis (L.), Hypericum maculatum (Cr.), Festuca rubra (L.), and Nardus stricta (L.), using the gas exchange technique. Leaf temperature (T L) of all species was adjusted within the range 13-30°C using the Peltier thermoelectric cooler. The temperature responses of metabolic processes were subsequently modelled using the Arrhenius exponential function involving the temperature coefficient Q 10. The expected increase of global temperature led to a significant increase of dark respiration rate (R D; Q 10 = 2.0±0.5), maximum carboxylation rate (V Cmax; Q 10 = 2.2±0.6), and maximum electron transport rate (J max; Q 10 = 1.6±0.4) in dominant species of mountain grassland ecosystems. Contrariwise, the ratio between J max and V Cmax linearly decreased with T L [y = -0.884 T L + 5.24; r 2 = 0.78]. Hence temperature did not control the ratio between intercellular and ambient CO2 concentration, apparent quantum efficiency, and photon-saturated CO2 assimilation rate (P max). P max primarily correlated with maximum stomatal conductance irrespective of T L. Water use efficiency tended to decrease with T L [y = -0.21 T L + 8.1; r 2 = 0.87]. © 2007 Institute of Experimental Botany, ASCR.