Application to wheat and barley of two leaf photosynthesis models for C3 plants

Two models describing the relationship between net photosynthesis of leaves of C3 plants, light intensity and CO2 concentration in the substomatal cavities are described and fitted to data obtained in a constant environment cabinet and in the field. The first model, based on a resistance analogue for gaseous diffusion and Michaelis‐Menten biochemistry, gave the best fit to the data. For the field data, four parameters were required–quantum yield, mesophyll resistance, ‘dayrsquo; respiration and a photorespiration constant. For the cabinet data, a parameter representing the limiting photosynthesis rate was required. The second model, based on a recent more rigorous biochemical analysis of photosynthesis, contains five parameters–quantum yield, maximum carboxylation rate, ‘day’ respiration, a photorespiration constant and a maximum electron transport rate. It fitted the data less well.