Illuminating plant water dynamics: the role of light in leaf hydraulic regulation.

Light intensity and quality influence photosynthesis directly but also have an indirect effect by increasing stomatal apertures and enhancing gas exchange. Consequently, in areas such as the upper canopy, a high water demand for transpiration and temperature regulation is created. This paper explores how light intensity and the natural high Blue-Light (BL) : Red-Light (RL) ratio in these areas, is important for controlling leaf hydraulic conductance (K leaf ) by BL signal transduction, increasing water permeability in cells surrounding the vascular tissue, in supporting the enormous water demands. Conversely, shaded inner-canopy areas receive less radiation, have lower water and cooling demands, and exhibit reduced K leaf due to diminished intensity and BL induction. Intriguingly, shaded leaves display higher water-use efficiency (compared with upper-canopy) due to decreased transpiration and cooling requirements while the presence of RL supports photosynthesis.