© 1986 Heron Publishing—Victoria, Canada
Stomatal and nonstomatal limitations to net photosynthesis in Pinus taeda L. under different environmental conditions
R. O. Teskey, J. A. Fites, L. J. Samuelson and B. C. Bongarten
School of Forest Resources, University of Georgia, Athens, GA 30602, USA /
Summary
Net photosynthesis, transpiration and stomatal conductance of two-year-old Pinus taeda L. seedlings were compared under various environmental conditions. Responses to air temperature, irradiance, ambient CO2 concentration, absolute humidity deficit and xylem pressure potential were examined. The seedlings exhibited little response
to a wide range of absolute humidity deficits (7 to 16 g m–3) and temperatures (20 to 35 °C), but were sensitive to changes in water deficit, irradiance and CO2 concentration. Net photosynthesis and stomatal conductance were linearly related under all of the environmental conditions
measured. However, the gas phase limitation to photosynthesis was generally small (20 to 30%). It was concluded that although
the stomatal response was closely coupled to changes in photosynthesis, internal limitations, rather than the rate of gaseous
diffusion of CO2, were primarily responsible for limiting photosynthesis.
