A new analytical model for whole-leaf potential electron transport rate (vol 27, pg 1447, 2004)

A new analytical model for the response of whole-leaf potential electron transport rate (J) to light is presented. The model treats incident irradiance at the upper and lower leaf surfaces independently, describes transdermal profiles of light absorption and electron transport capacity explicitly, and calculates J by integrating the minimum of light- and capacity-limited rates among paradermal chlorophyll layers. The capacity profile is assumed to be a weighted average of two opposed exponential profiles, each of which corresponds to the profile of light- limited rate when only one surface is illuminated; the weights may take on any values, provided they sum to unity, so the model can describe leaves with a wide range of 'preferred' illumination regimes. By treating irradiance at either surface independently and assuming the capacity profile is fixed on short time scales, the model predicts observed effects of leaf inversion on light- response curves and their apparent convexity. By assuming the capacity profile can adapt on developmental time scales, the model can predict the observed dependence of inversion effects on the growth lighting regime. It is suggested that the new model, which is mathematically compact and formally similar to the standard non-rectangular hyperbola model for J, be used in place of the standard model in studies in which the effects of leaf angle or diffuse light fraction on gas exchange are of interest.