A model of net photosynthesis for leaves of the sclerophyll Quercus coccifera

Abstract

In the past decade, a considerable research effort has been invested in defining single factor dependencies of leaf net photosynthesis mathematically and in terms of physiologically meaningful parameters (Tenhunen et al. 1980a; Farquhar and von Caemmerer 1982; Harley et al. 1985, 1986; Weber et al. 1985). The single factor dependencies have been combined to define leaf CO₂ gas exchange rate as a function of incident light intensity, leaf temperature, and leaf internal CO₂ partial pressure (Tenhunen and Westrin 1979). One set of information which allows description of CO₂ uptake by leaves in the natural environment includes 1) the temperature dependency of net photosynthesis rate at light and CO₂ saturation (P_ML), 2) light dependencies of net photosynthesis rate at CO₂ saturation (P_M) at a series of temperatures, 3) light and temperature dependencies of leaf carboxylation efficiency CE - the initial slope of the net photosynthesis response (NP) to internal leaf air space CO₂ pressure and 4) the temperature dependency of dark respiration (R_d - assumed to continue in the light). While data describing all four of these is essential, the fundamental dependency in an appropriate photosynthesis model is the leaf response to internal CO₂ pressure. The other dependencies are utilized to describe variation in those parameters which establish an appropriate response to internal CO₂ pressure for particular light and temperature conditions prevailing at any point in time.