Clamping Experiment
We tested the impacts of repeated clamping on leaves of Capsicum annuum , Populus deltoides , and Populus trichocarpa . For each of five sequential clamps on each measured leaf, we allowed the chamber to stabilize (< 2 min in all cases), and measuredAnet at 400 μmol CO2mol-1 for 30 s at 0.5 Hz. Between clamps, the leaf was given a 1 min recovery. On clamps 1 and 5, a RACiR was run as specified above for each species. We then fit Vcmax andJmax­ as above. These measurements were performed on an individual leaf spot within 30 min to minimize diurnal effects.