Photosynthesis in Sitka Spruce (Picea sitchensis (Bong.) Carr.). I. General characteristics.
A study of net photosynthesis, respiration, and stomatal and mesophyll resistance of 3- to 4-year-old Sitka Spruce seedlings, grown in a greenhouse, in relation to irradiance, temperature, ambient CO2, O2, and water vapour concentrations, needle age, and provenance. Results establish the presence and magnitude of photorespiration in Sitka Spruce, and demonstrate its close association with photosynthesis. There was a tendency for maximum net photosynthesis to be greater, and for stomatal and mesophyll resistance to be less in the more northerly than in the southern provenances. The rate of photosynthesis of young shoots in the spring increased with elongation, and in conjunction with this increase there was a marked decline in mesophyll resistance and a smaller decline in stomatal resistance. As needles aged further, photosynthesis declined in association with a large increase in stomatal resistance, while the mesophyll resistance remained about the same.
Photosynthesis \ Picea sitchensis physiology