Data from: Grassland plants show no relationship between leaf drought tolerance and soil moisture affinity, but rapidly adjust to changes in soil moisture

1. Assessing drought tolerance and the ability of plants to adjust to
changes in available water resources is crucial for understanding current
and future distributions of plant species. While turgor loss point (πtlp)
has been recognized as a direct determinant of drought tolerance in woody
plants, information on it for grassland species is largely missing. 2. We
first validated a rapid method to estimate πtlp for grassland species,
using osmometry measurements (πtlp-osm) of osmotic potential at full
hydration (πo-osm), originally proposed for woody species. We confirmed
that πo-osm was tightly positively related to πtlp measured by the classic
pressure–volume curve (πtlp-pv). Cell wall elasticity was not important in
the maintenance of turgor and neither specific leaf area nor leaf dry
matter content influenced πtlp. 3. We then studied the relationship
between πtlp-osm measured under controlled conditions and species’ soil
moisture affinity (Ellenberg indicator values) in 40 diverse grassland
species from the full range of soil moisture conditions found in temperate
grasslands. On a subset of 12 species, we studied the adjustment in
πtlp-osm to drought stress and recovery from drought. 4. We hypothesized
that dry grassland species are better adapted to drier conditions by
having comparatively higher leaf drought tolerance (more negative πtlp)
and a better ability to adjust to acute drought stress. 5. We found that
πtlp-osm was unrelated to species’ soil moisture affinity. However, all
species developed higher leaf drought tolerance by decreasing πtlp-osm
after seven weeks of drought stress. After only one week of recovery, all
species reduced the leaf drought tolerance back to the πtlp-osm level
comparable with non-stressed plants. 6. Our results considerably extend
the relationship between πo-osm and πtlp, originally defined for woody
species, and thus propose a yet unexploited direct method for assessing
leaf drought tolerance via turgor loss point in herbaceous species.
However, the lack of relationship between πtlp and soil moisture affinity
suggests that, unlike in woody plants, leaf-level drought tolerance in
grassland plants does not fully translate into whole-plant drought
resistance, suggesting an importance of other drought resistance
strategies.