Foliar uptake and physiology of California shrub species

Background/Question/Methods

Fog can be a significant force in shaping plant communities, particularly in coastal regions such as in California where it ameliorates summer temperatures and reduces drought stress. In southern California, fog tends to occur during the late summer during the peak of the drought season. The occurrence and seasonality of fog suggests the potential for coastal shrub species to take advantage of this water source. Foliar uptake of fog has been demonstrated in northern California where fog is more frequent. However, foliar uptake in coastal shrub species of central and southern California is unknown. This study consisted of a greenhouse experiment with artificial fog events to investigate overnight foliar hydration and changes to physiology in five shrub species. We used deuterated fog to track foliar uptake into leaf tissue.

Results/Conclusions

We determined that foliar uptake likely occurs in some shrub species and not others. The evergreen shrub species with sclerophyllous leaves showed no alterations to their physiology. While almost all species showed decreases in photosynthesis during the experiment, the two drought-deciduous species exposed to fog overnight maintained their photosynthetic capacity throughout the experimental period. This suggests that fog not only reduces drought stress but can enhance early morning photosynthesis in some shrub species during periods of reduced water availability. To understand the context and importance of this novel water use, it is important to determine the long term effects of fog inundation along the California coast.