Figure 6.

A hypothetical model for the role of PhyB in regulating systemic stomatal aperture closure responses and ROS wave initiation during light stress. Excess white light stress is shown to be sensed by PhyB, leading to local accumulation of ROS, closure of stomatal aperture in local leaves, and triggering of the ROS wave. The ROS wave is shown to induce a state of high ROS accumulation in systemic leaves for up to 6 h and to trigger stomatal aperture closure in systemic leaves. Stomata in systemic leaves are shown to remain closed for at least 3 h. PhyB could be playing a paramount role in triggering local and systemic responses to light stress in Arabidopsis, and these responses are maintained in systemic tissues for up to 3 to 6 h, potentially serving as a systemic stress memory mechanism. Yellow arrows indicate pathways proposed by this study, and blue dashed arrows represent additional possible pathways.