Physiological basis for light use efficiency models
2002
Rosati, A. | DeJong, T.M. | Esparza, G.
Modeling whole canopy photosynthesis is a fundamental step in orchard modeling. Simplification of this step is desirable in order to obtain practical and effective models. Light use efficiency models are very simple models of crop productivity, which are based on the proportionality between net primary productivity (NPP) and absorbed photosynthetically active radiation (APAR). Physiological bases for this relationship have been theorized. However, in real canopies, with the varying light conditions of the field, the existance of a linear relationship between photosynthesis and intercepted light of single leaves has not been tested. In the present study the daily leaf photosynthesis was estimated from measured (i.e. not modeled) leaf photosynthetic properties and from measured leaf intercepted irradiance on both peach trees and eggplant plants, grown with either abundant or scarce nitrogen fertilization. Daily leaf photosynthesis was linearly related to daily leaf intercepted irradiance (which implies constant light use efficiency), and the slope of this relationship increased with N fertilization. This slope did not change under either sunny or overcast weather. This slope (i.e. the light use efficiency) could be calculated with good approximation from the photosynthetic properties (i.e. the photosynthetic light response curve) of top-canopy leaves and from incoming PAR, which can be obtained from weather stations. Thus, canopy photosynthesis can be estimated from canopy intercepted radiation and from the crop’s light use efficiency, the latter being estimated simply from the light response curve of upper canopy leaves.
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