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Linking the main physiological processes driving drought-induced tree mortality: a focus on leaves cells
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Edité par CCSD -
3ème prix de la meilleure communication. National audience. Global climatic models predict an increment in the frequency and intensity of drought events which have already shown to have important consequences on tree survival and forest dieback. Results from a first experiment showed that the actual thresholds used for recovery from drought based on percentage loss of conductance (PLC) (i.e., 50% for conifers, 88% for angiosperms) do not provide accurate insights about the tree capacity for surviving extreme drought events. Therefore, it is crucial to identify and understand not only the mechanisms leading to tree mortality under extreme drought conditions but also the physiological thresholds beyond which trees die. This information will help to improve the predictions of mechanistic models predicting tree mortality and thus improve our forests distribution predictions. Differences in stem relative water content (RWCStem) and the level of electrolytes leakage (EL) were directly related to the capacity of the trees to recover from drought. Thus, one of the main causes of drought-induced tree mortality should be the direct cellular consequences of dehydration. Indeed, as a tree approaches its critical water status, it should enter the phase of cell death in which dehydration tolerance becomes important in delaying mortality. However, the link between the RWC and cell mortality has not been properly evaluated yet. Therefore, we exposed to water-stress plants from three different species showing different resistance to drought. As the stress became more severe, we monitored in leaves the level of EL and determined a threshold in RWC below which the leaves suffered an irreversible destruction of their cells. Whether this cellular death is due to cell cavitation or to the collapse and cytorrhysis of the cell is still unclear. Thus, we plan to use cryo-SEM techniques to answer this question
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