LACK OF AGREEMENT AMONG MODELS FOR ESTIMATING THE PHOTOSYNTHETIC PARAMETERS

Comparisons were conducted between estimates of photosynthetic capacity (P(max)) and photosynthetic efficiency (alpha) calculated with different models of the photosynthesis vs. irradiance curve. Values computed on the same data sets are different according to the models used. Estimates for P(max) with the exponential and hyperbolic tangent models (without a term for photoinhibition) are in good agreement (4% difference). The same comparison for a shows poor agreement (24% difference between the two models). When a parameter for the intercept is added to the two models, the lack of agreement increases to 8% for P(max) and 46% for alpha. When the mean photosynthetic parameters calculated with the two models are introduced into various published models for calculating primary production, differences in the resulting estimates range between 20 and 133%. Comparing the exponential model with a term for photoinhibition to the hyperbolic tangent model (without a term for photoinhibition) shows a 24% difference in the estimate of alpha. Equations are given for transforming values calculated with the various models.