Stomatal responses to non-local changes in PFD: Evidence for long-distance hydraulic interactions

Abstract

Interactions among stomata within a single areole have recently been reported, and evidence suggests that hydraulic mechanisms may be responsible for these interactions. Such interactions may play a role in patchy stomatal behaviour by coordinating stomatal behaviour within areoles. However, models suggest that longer-distance interactions may be required to produce the large-scale dis-coordination that is characteristic of stomatal patchiness. This study was undertaken to characterize long-distance interactions between 'artificial patches' of stomata under varying conditions of evaporative demand and soil water stress. Gas-exchange was monitored in two adjacent regions ('patches') of a wheat leaf by two independent gas mixing and analysis systems. When photon flux density (PFD) was changed in only one of these patches, stomatal conductance responded in both patches in a manner consistent with hydraulic interactions propagated by changes in xylem water potential. These data are discussed in the context of mechanisms for patchy stomatal conductance and implications for the design and analysis of gas-exchange experiments.