Climatic warming changes plant photosynthesis and its temperature dependence in a temperate steppe of northern China

Warming responses of photosynthesis and its temperature dependence in two C-3 grass (Agropyron cristatum, Stipa krylovii), one C-4 grass (Pennisetum centrasiaticum), and two C-3 forb (Artemisia capillaris, Potentilla acaulis) species in a temperate steppe of northern China were investigated in a field experiment. Experimental warming with infrared heater significantly increased daily mean assimilation rate (A) in P centrasiaticum and A. capillaris by 30 and 43%, respectively, but had no effects on other three species. Seasonal mean A was 13, 15, and 19% higher in the warmed than control plants for P. centrasiaticum, A. capillaries, and S. krylovii, respectively. The mean assimilation rate in A. cristatum and P acaulis was not impacted by experimental warming. All the five species showed photosynthetic acclimation to temperature. The optimum temperature for photosynthesis (T-opt) and the assimilation rate at Topt in the five species increased by 0.33-0.78 degrees C and 4-27%, respectively, under experimental warming. Elevated temperature tended to increase the maximum rate of ribulose-1,5-bisphosphate (RuBP) carboxylation (V-cmax) and the RuBP regeneration capacity (J(max)) in the C-3 Plants and carboxylation efficiency and the CO2-saturated photosynthetic rate in the C-4 Plant at higher leaf temperature, as well as the optimum temperatures for the four parameters. Our results indicated that photosynthetic responses to warming were species-specific and that most of the species in the temperate steppe of northern China could acclimate to. a warmer environment. The changes in the temperature dependence of V-cmax and J(max), as well as the balance of these two processes altered the temperature dependence of photosynthesis under climatic warming. (c) 2007 Elsevier B.V. All rights reserved.