The hyperbolic tangent (as well as other) formulations for the photosynthesis-
irradiance (P-I) function have been derived by several workers, using both
empirical and theoretical approaches. A few references are:
Chalker, B.E. 1980. Modelling light saturation curves for photosynthesis: An
exponential function. J. Theoretical Biology 84: 205-215.
Gallegos, C.L. and Platt T. 1981. Photosynthesis measurements on natural
populations of phytoplankton: numerical analysis. In: "Physiological bases of
phytoplankton ecology", Platt, T. (ed.), Canadian Bulletin Fisheries and
Aquatic Sciences 210: 103-112.
Jassby, A.D. and Platt T. 1976. Mathematical formulation of the relationship
between photosynthesis and light for phytoplankton. Limnology and Oceanography
21: 540-547.
Hope this helps.
Pat
-------------------------------------------------------------------
Patrick Neale
Smithsonian Environmental Research Center
P.O. Box 28
Edgewater MD 21037 410-798-4424 FAX 301-261-7954
