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Fonds National Suisse de la Recherche Scientifique (FNSRS) 2021

Structural and biochemical changes in leaves below turgor loss point : Implications for cellular, physiological and ecosystem drought responses

Drought Leaves Turgor

Titre : Structural and biochemical changes in leaves below turgor loss point : Implications for cellular, physiological and ecosystem drought responses

Numéro  : 203127

Début/Fin : 01.09.2021 - 31.08.2023

Requérant  : Schönbeck Leonie
Institution de Recherche : Dept. of Botany & Plant Sciences UC Riverside

Résumé
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. The turgor loss point (pTLP), the water potential at which cells lose water pressure and undergo plasmolysis causing leaf wilt, is a key point in the plant response to drought. Yet, the mechanisms and consequences of leaf turgor loss are far from understood, as is the relationship between cell structural traits, leaf hydraulic function, and other traits such as rooting depth that can buffer the plant from water deficit.The objectives of this study are to (1) resolve the cell structural traits that may enable some species to regain cell shape with rehydration after turgor loss ; (2) determine how species with contrasting water use strategies differ in their leaf structural and biochemical mechanisms for surviving turgor loss ; and (3) understand linkages between aboveground leaf structural and biochemical characteristics and belowground rooting strategies that determine water uptake. The 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. Extremely drought-tolerant native Californian shrubs have never been examined at the cellular level, so the mechanisms by which they respond to turgor loss are unknown. 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.The work will take place in southern California ecosystems that expose plants to some of the lowest water potentials in the world, and will explore the seldom studied, but critically important link between ecophysiology and cell biology. 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.

Mots clés : leaf cell structure ; drought ; hydraulics ; rooting depth ; Californian Chaparral ; leaf turgor loss

Fonds National Suisse de la Recherche Scientifique

Page publiée le 20 août 2022