Measured leaf dark respiratory CO 2 -release is not controlled by stomatal conductance.

Leaf dark respiratory CO 2 -release (R D ) is, according to some literature, dependent on the rate of leaf transpiration. If this is true, then at a given vapor pressure deficit, the leaf stomatal conductance (g s ) will be expected to be a controlling factor of measured R D at any given time. We artificially lowered leaf g s by applying abscisic acid (ABA). Although leaf R D generally covaried temporally with g s , artificially lowering g s by applying ABA does not affect the measured leaf R D . These results indicate that observed diel fluctuations in g s are not directly influencing the measured leaf R D , thereby simplifying both future studies and the interpretation of past studies of the underlying environmental- and physiological drivers of temporal variation in leaf R D .