Abstract
Increase in severity and frequency of drought events is altering plant community composition, exposing biomes to a higher risk of biodiversity losses. This is exacerbated in the most fragile areas as Mediterranean biome. Thus, identifying plant traits for forecasting species with a high risk of drought-driven mortality is particularly urgent. In the present study, we investigated the drought resistance strategy of two Mediterranean native species: Salvia ceratophylloides Ard. (Sc) and Salvia officinalis L. (So) by considering the impact of drought-driven water content decline on plant hydraulics. Well-watered samples of Sc displayed higher leaf and stemsaturated water content and lower shoot biomass than So samples, but similar root biomass. In response to drought, Sc showed a conservative water use strategy, as the prompt stomatal closure and leaves shedding suggested. A drought-tolerant mechanism was confirmed in So samples. Nevertheless, Sc and So showed similar drought-driven plant hydraulic conductance (Kplant) recover ability. Root hydraulic traits played a key role to reach this goal. Relative water content as well as loss of cell rehydration capability and membrane damages, especially of stem and root, were good proxies of drought-driven Kplant decline.
Highlights
We reported the hydraulic performance, including changes in relative water content, of two native Mediterranean species, Salvia ceratophylloides Ard. (Sc), a perennial herbaceous species [31,32,33], and Salvia officinalis L. (So), a perennial evergreen subshrub [34], experiencing mild and severe drought events and rewatering
The two study species showed similar root dry mass but a 3-times higher root/shoot ratio value was recorded in Sc compared to So plants
Cell membrane damages in fine roots. Overall, these results strongly suggest that root hydraulics plays a key role in whole-plant recovery these results strongly suggest that root hydraulics plays a key role in whole-plant recovery ability of the two Mediterranean native Salvia species
Summary
The increase in severity and frequency of drought events is exposing vegetation to a higher risk of drought-driven die-off [1,2,3]. Global warming is not expected to be homogeneous: higher increase in temperature and drought events have been forecasted for the Mediterranean region e.g., [4,5,6]. This, in turn, may lead to more relevant negative feedback on biodiversity richness of the Mediterranean biome, exacerbating the recorded ongoing vegetation pattern shifts [7,8,9,10] and increasing the extinction risk of endemic flora [11,12,13]. The high numbers of endemic plant species are adapted to cope with warm and frequently long dry periods that typically occur in the Mediterranean biome. Many questions on plant hydraulics remain unresolved [22,25] and looking for a robust proxy for predicting plant die-back is urgent
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