AN ADEQUATE MODEL OF PHOTOSYNTHESIS .2. DEPENDENCE OF PARAMETERS ON ENVIRONMENTAL-FACTORS

Models of photosynthesis are commonly written as functions of light, t emperature and CO2 concentration ([CO2]). In an ideal model, the param eter values would be independent of these environmental factors. Howev er, there is no ideal photosynthesis model, so it is necessary to know how the parameters vary in response to the environment. Three of the most popular models of photosynthesis were fitted to experimental data for tomato plants, including light response curves measured at temper atures of 18, 25 and 32 degrees C and [CO2] of 100, 350, 700 and 1000 vpm. Statistical analysis of parameter values allowed us to find their dependencies on environmental factors. Light utilization efficiency o c proved to be constant at ambient and elevated [CO2]. Values of alpha at 100 mu l l(-1) [CO2] were approximately half of those at 350, 700 and 1000 mu l l(-1) [CO2]. Leaf conductance for CO2 transfer tau depen ded on temperature as well as on [CO2]. Two other parameters, one conn ected with respiration, R and Farquhar's 'curvature factor' theta, wer e both linearly dependent on temperature.