Description

The present study focuses on the impacts of extreme drought on Arctostaphylos glauca. This image represents the impressive abilities of these drought tolerant shrubs to take advantage of precious summer fog. Events like this one temporarily saturate the topsoil and provide much-needed relief.

What at first glance appears to be morning dew on A. glauca (bigberry manzanita) may actually be evidence of a process called “guttation”: the secretion of sap water through specialized glands in the leaf tips called hydathodes. As opposed to transpiration (the typical “pulling” action in which open stomata draw water up through the plant from its roots by negative pressure potentials), guttation occurs when the stomata are closed. High soil moisture drives positive root pressure that pushes water up through the plant and out of the specialized pores, creating the beadlike structures seen in the photograph.