The team also collected for the first time drought-tolerance trait data for species worldwide, which confirmed their result. Across species within geographic areas and across the globe, drought tolerance was correlated with the saltiness of the cell sap and not with the stiffness of cell walls. In fact, species with stiff cell walls were found not only in arid zones but also in wet systems like rainforests, because here too, evolution favors long-lived leaves protected from damage.
The pinpointing of cell saltiness as the main driver of drought tolerance cleared away major controversies, and it opens the way to predictions of which species could escape extinction from climate change, Sack said.
"The salt concentrated in cells holds on to water more tightly and directly allows plants to maintain turgor during drought," said research co-author Christine Scoffoni, a UCLA doctoral student in the department of ecology and evolutionary biology.
The role of the stiff cell wall was more elusive.
"We were surprised to see that having a stiffer cell wall actually reduced drought tolerance slightly contrary to received wisdom but that many drought-tolerant plants with lots of salt also had stiff cell walls," said lead author Megan Bartlett, a UCLA graduate student in the department of ecology and evolutionary biology.
This seeming contradiction is explained by the secondary need of drought-tolerant pla
|Contact: Stuart Wolpert|
University of California - Los Angeles