Photosynthetic irradiance-response in leaves of dwarf coconut palm (Cocos nucifera L. ‘nana’, Arecaceae): Comparison of three models

Experimental data of irradiance-response curves of photosynthesis, obtained from independent experiments with the Brazilian Green Dwarf coconut palm genotype, were used to fit three empirical models with the aim to compare their adequacies. The non-rectangular and rectangular hyperbolas and the exponential models were compared. The rectangular hyperbola and the exponential models were quantitatively adequate to describe the irradiance-response of photosynthesis in dwarf coconut in all the situations studied. The photosynthetic parameters showed good correlation with the measured values when estimated by the rectangular hyperbola and exponential but the later estimated a more realistic light-saturated rate and the apparent quantum yield of photosynthesis. The NRH was less adequate for estimate the light-saturated photosynthesis and dark respiration universally, but could be used for research purposes since it contains an important qualitative parameter, the convexity term relating physical to total resistances to CO2 diffusion into the chloroplasts. The results allow suggesting the exponential model as a rapid, simple, quantitatively and qualitatively adequate option for accessing information from the photosynthetic irradiance-response in dwarf coconut palm.