Photosynthesis and Carbon Dioxide Transfer Resistance of Lodgepole Pine Seedlings in Relation to Irradiance, Temperature, and Water Potential

Abstract

Photosynthesis and stomatal and total equivalent mesophyll resistances to CO 2 transfer were measured in relation to irradiance, needle temperature, and tree water potential. Maximum rates of net photosynthesis were attained at 380 W m −2 irradiance, 20 °C needle temperature, and the highest tree water potential obtained, ca. −2.5 bars. Stomatal and total mesophyll resistances have a significant rate-limiting role when environmental conditions are less than optimum. Mesophyll resistance was larger than stomatal resistance under all environmental conditions.