Drought survival is positively associated with high turgor loss points in temperate perennial grassland species

Turgor loss point (pi(tlp)) has been suggested to be a key trait for drought resistance in woody species. In herbaceous grassland species, the role of pi(tlp) for species drought survival has not yet been tested, although grasslands are projected to experience more frequent and intense droughts with climate change. To gain insights into the role of pi(tlp) for drought resistance of temperate perennial grassland species, we assessed pi(tlp) of 41 species common in Germany (20 forbs, 21 grasses). We directly related them to the species' comparative whole-plant drought survival and midday leaf water potentials under drought (psi(MD)) assessed in a common garden drought experiment, and to species moisture association. Species drought survival increased with increasing pi(tlp) across all species as well as within forbs or grasses separately. psi(MD) was positively related to pi(tlp) and drought survival. Our results imply that high pi(tlp) promotes drought survival of common perennial European temperate mesic grassland species by enabling them to maintain high leaf water potentials under drought, that is, a desiccation avoidance strategy. However, pi(tlp) was not related to species moisture association. The positive relationship between pi(tlp) and drought survival in herbaceous grassland species was opposite to the negative relationship previously established in woody plants, implying that mechanisms of drought resistance differ between woody and herbaceous species. Our results highlight the necessity of directly testing the relationship of functional traits to whole-plant drought survival in different plant life forms, before using trait assessments for predicting plant responses to drought. A free plain language summary can be found within the Supporting Information of this article.