LEAFSHED (BioGeCO / ISPA / EGFV)
An integrated approach to understand the contribution of leaf shedding in tree responses to drought.
There remains considerable uncertainty in how rainfall amounts and patterns will change in the future, but there is already evidence that tree mortality attributed to drought and heat stress has started to increase in many regions of the world. Understanding and predicting the response and mortality of woody plants to extreme water limitation represents a major challenge for the carbon cycle and climate community, and the forest and wine industry. Limiting dehydration of perennial organs (stem) during drought is essential for survival and can be achieved by reducing the amount of transpiring organs, mostly by leaf shedding. The pathways leading to leaf shedding are very well described at the molecular level but rarely studied at the whole plant level. Recent techniques revealed also that some leaves become hydraulically isolated from the stem before any visible sign of senescence appears. However, whether this mechanism is ubiquitous amongst species and quantitatively relevant for drought tolerance is still unknown.
Within LEAFSHED we will set up a drought-controlled experiment in order to investigate, at the whole-plant level, the processes of leaf hydraulic isolation and leaf shedding during an extreme drought in a diverse range of perennial plant species from distant families and contrasted leaf lifespans. We will use innovative optical and stable isotope tracing techniques to characterize the amount of hydraulic isolation, and measure drought- and senescence-related hormones and gene expression to better understand the triggers and sequence of events leading to leaf shedding during extreme droughts. A model of drought-induced leaf shedding will then be developed and implemented in an ecosystem model to investigate the consequences for plant survival under extreme droughts.