Instantaneous Q of night-time leaf respiratory CO efflux - measurement and analytical protocol considerations.

The temperature sensitivity (e.g. Q) of night-time leaf respiratory CO efflux (R) is a fundamental aspect of leaf physiology. The Q typically exhibits a dependence on measurement temperature, and it is speculated that this is due to temperature-dependent shifts in the relative control of leaf R. Two decades ago, a review hypothesized that this mechanistically caused change in values of Q is predictable across plant taxa and biomes. Here, we discuss the most appropriate measuring protocol among existing data and for future data collection, to form the foundation of a future mechanistic understanding of Q of leaf R at different temperature ranges. We do this primarily via a review of existing literature on Q of night-time R and only supplement this to a lesser degree with our own original data. Based on mechanistic considerations, we encourage that instantaneous Q of leaf R to represent night-time should be measured: only at night-time; only in response to short-term narrow temperature variation (e.g. max. 10°C) to represent a given midpoint temperature at a time; in response to as many temperatures as possible within the chosen temperature range; and on still attached leaves.