Structural and biochemical changes in leaves below turgor loss

Changing precipitation patterns, including more frequent droughts, pose a serious threat to terrestrial ecosystems. Mediterranean ecosystems experience warm dry summers, exposing plant species to extremely low water potentials, and represent a model for what many ecosystems will experience in the future. Understanding ecosystem resilience to extreme droughts requires resolving the mechanisms of hydraulic decline during drought in plants. 

Plants have a multitude of possibilities for adjustment to extreme drought. They can develop deep rooting systems for better access to water sources, they can invest energy in tough organs that can withstand strong water potentials, or they can prevent water loss by closing their stomata early. 

In this project, I try to resolve the tight connections between belowground and aboveground plant processes, and to find key trait combinations that help native Californian plants surviving the erratic climate in Southern California. These plants may have to deal with multiple years of extreme drought, and thereafter extreme rainfall. 

This study, focused on unique Native Californian shrubs adapted to extreme drought, combines greenhouse experiments for a strong mechanistic basis and field sampling for understanding processes during actual drought under natural conditions. Evergreen and deciduous shrub species with contrasting hydraulic behaviors will be grown in the greenhouse under wet and dry treatments and sampled in the field during wet and dry seasons. At the cellular level, well established imaging techniques will be used to quantify leaf cellular structural traits expected to play a role during turgor loss, including microfibril properties and vacuole size. At the leaf level, standard hydraulic traits will be measured to link cellular structure below turgor loss point to innate drought resistance. At the ecosystem level, individual and species differences in depth of water uptake will be assessed using 18O and 2H stable isotope analysis in the soil and xylem to quantify whether access to water forms a trade-off with leaf drought resistance.

A full assessment of cell-to-ecosystem hydraulic function will allow us to resolve the drivers of hydraulic decline during drought, improving our understanding of drought tolerance in natural ecosystems and enabling translation to agricultural crops and forestry, where research and development of drought-tolerance is highly needed.