Estimating stomatal and biochemical limitations during photosynthetic induction

Deans RM, Busch FA and Farquhar GD

Research School of Biology 46 Sullivans Creek Rd The Australian National University Acton ACT.

Ross M. Deans, Florian A. Busch and Graham D. Farquhar Research School of Biology 46 Sullivans Creek Road The Australian National University Acton ACT Understanding what limits photosynthesis under different conditions is important for both the targeted improvement of photosynthesis as well as understanding ecological drivers of photosynthesis. Limitation analyses provide such a method to estimate photosynthetic limitations. Despite the use of limitation analyses to calculate biochemical and diffusional limitations at the leaf level being not new, their utility for estimating limitations during photosynthetic induction is still in its infancy. Moreover, few studies have systematically assessed how well different methods estimate limitations. Timecourses of photosynthetic induction provide a rich dataset in which to test the performance of limitation analyses. We compared how well two general ways of estimating limitations predicted both temporal and overall limitations for photosynthetic induction in response to an increase in irradiance. One method sequentially removes the effect of a limitation (elimination), while the other utilised a tangent plane approximation (differential) to estimate limitations. This talk will discuss under what conditions each method works best and why. This last insight has important implications for the general use of limitation analyses beyond photosynthetic induction.