Physiological basis of seasonal trend in leaf photosynthesis of five evergreen broad-leaved species in a temperate deciduous forest

The physiological basis of photosynthesis during winter was investigated in saplings of five evergreen broad-leaved species (Camellia japonica L., Cleyera japonica Thunb., Photinia glabra (Thunb.) Maxim., Castanopsis cuspidata (Thunb.) Schottky and Quercus glauca Thunb.) co-occurring under deciduous canopy trees in a temperate forest. We focused on temperature dependence of photosynthetic rate and capacity as important physiological parameters that determine light-saturated rates of net photosynthesis at low temperatures during winter. Under controlled temperature conditions, maximum rates of ribulose bisphosphate carboxylation and electron transport (V_cmax and J_max, respectively) increased exponentially with increasing leaf temperature. The temperature dependence of photosynthetic rate did not differ among species. In the field, photosynthetic capacity, determined as V_cmax and J _max at a common temperature of 25°C (V_cmax ⁽²⁵⁾ and J_max⁽²⁵⁾), increased until autumn and then decreased in species-specific patterns. Values of V_cmax ⁽²⁵⁾ and J_max⁽²⁵⁾ differed among species during winter. There was a positive correlation of V_cmax⁽²⁵⁾ with area-based nitrogen concentration among leaves during winter in Camellia and Photinia. Interspecific differences in V_cmax⁽²⁵⁾ were responsible for interspecific differences in light-saturated rates of net photosynthesis during winter.