Photosynthesis and Stomatal Behaviour

Abstract

In order for plants to use water efficiently, stomata must ensure an appropriate balance between CO2 demands for photosynthesis and water loss through transpiration. To achieve this, stomatal conductance (gs) often correlates with mesophyll photosynthetic rates. However, the underlying mechanisms and signals that promote this relationship are currently unknown. Stomata and photosynthesis respond to a number of environmental cues; however, the dynamics and magnitude of these responses are not identical, with stomatal responses generally an order of magnitude slower than mesophyll photosynthesis. The resulting disconnection between stomatal conductance and photosynthetic rate means that under naturally fluctuating environmental conditions water use efficiency (WUE) can be far from optimal. Manipulation of stomatal behaviour provides an obvious mechanism for producing plants with improved WUE; however, before such an approach is possible we must first understand the hierarchy of stomatal responses to varying environmental parameters, the mechanisms behind these complex signalling pathways,and how stomatal behaviour is tuned to mesophyll photosynthetic rates or capacity.