Mind the cuticle conductance: When resistance to cavitation is not enough for evaluating resistance to drought.
Résumé
In the actual global warming context, drought events will tend to be more intense and more frequent, increasing the risk of dessication and death for plants induced by hydraulic failure. Under drought conditions, the higher atmospheric demand for water together with reduced water availability for plants increase the xylem tension until the xylem water columns break due to cavitation. To avoid reaching such risky xylem tensions, plants close their stomata to reduce the amount of water lost by transpiration and, therefore, keep the water potential relatively constant. However, despite stomatal closure, there are still some water losses through the plant cuticle (gmin) that keep the xylem tension decreasing. How efficient the plants are in reducing such water losses and how resistance are to cavitation (P50) will define the resistance of plant to drought. While the link between resistance to drought and P50 has been widely studied in the past, less is known about the link between drought resistance and variation in gmin. Indeed, gmin not only varies across species but also within species under different environmental conditions. We will evaluate here i) the link between gmin and cuticle composition; ii) the link between P5 0 and gmin, and iii) the role of gmin in plant resistance to drought.