Field evidence for the optimality hypothesis of gas exchange in plants

Abstract

The ‘optimality hypothesis’ of gas exchange in plants has been studied since the 1970s, but testing it in the field has proven difficult. A recent reformulation of the hypothesis with detailing assumptions on leaf structure makes it possible to solve the optimisation problem explicitly, such that the predictions of gas exchange are readily testable against field data. This form of the model was tested against field measurements of photosynthesis, transpiration and stomatal conductance in Scots pine (Pinus sylvestris) shoots during three clear summer days. Model parameters were estimated independently from photosynthesis measurements on preceding days. The measurements were carried out at a new field measurement station with a very low level of noise. The predictions of photosynthesis, transpiration andstomatal conductance explained 84–98% of the variance in the data.