Intercellular CO2 concentration and water-use efficiency of temperate plants with different life-forms and from different microhabitats.

Photosynthesis and transpiration were measured simultaneously, under near-optimum and constant environmental conditions, in intact leaves of plants native to the temperate forest region. A linear relationship between photosynthetic rate and stomatal conductance was found in every species tested irrespective of leaf age or season, indicating that the calculated intercellular CO2 concentration and water-use efficiency were fairly constant within a species. The values of intercellular CO2 concentration and water-use efficiency ranged from 221 to 271 μl l-1 [Formula: see text] and 4.46 to 8.20 μmol CO2 mmolH2O-1 (6.24±0.90 μmol CO2 mmolH2O-1), respectively. The variations in intercellular CO2 concentration and water-use efficiency were not directly related to photosynthetic capacities, life-forms, or microhabitat preferences. The intercellular CO2 concentrations found in this study were close to values reported from cultivated plants and plants native to more arid regions, suggesting a common mechanism to maintain the stomatal conductance proportional to photosynthetic capacity over a wide variety of C3 plants.