Biology subjects

Herbette, S.

Publications and source records attributed to Herbette, S..

3 recordsLinked to original sources

bioRxiv2020

Plasticity of the xylem vulnerability to embolism in poplar relies on quantitative pit properties rather than on pit structure

Knowledge on variations of drought resistance traits are needed to predict the potential of trees to acclimate to coming severe drought events. Xylem vulnerability to embolism is a key parameter related to such droughts, and its phenotypic variability relies mainly on environmental plasticity. We investigated the structural determinants controlling the plasticity of vulnerability to embolism, focusing on the key elements involved in the air bubble entry in a vessel, especially the inter-vessel pits. Poplar saplings (Populus tremula x alba) grown in contrasted water availability or light exposure exhibited differences in vulnerability to embolism in a range of 0.76 MPa. We then characterized the structural changes related to qualitative and quantitative pit characteristics, from the pit structure to the organization of xylem vessels, using different microscopy techniques (TEM, SEM, light). X-ray microtomography analysis allowed observing the vessel vulnerability and testing some of the relationships between structural traits and vulnerability to embolism inside the xylem. The pit ultrastructure did not change, whereas the vessel dimensions increased with vulnerability to embolism and the grouping index and fraction of inter-vessel cell wall decreased with vulnerability to embolism. These findings holds when comparing trees or when comparing vessels inside the xylem. These results evidenced that plasticity of vulnerability to embolism occurs through changes in the quantitative pit properties such as pit area and vessel grouping rather than on the pit structure.

plant biology↗

bioRxiv2020

Delayed effect of drought on the xylem vulnerability to cavitation in Fagus sylvatica L.

Knowledge on variations of drought resistance traits is needed to predict the potential of trees to adapt to severe drought events expected to be more intense and frequent. Xylem vulnerability to cavitation is among the most important traits related to drought-induced mortality and exhibits a large variability between species. Acclimation of this trait to environmental conditions implies changes in the xylem structure and organization, leading previous studies to investigate its variations under conditions preserving growth. In European beech saplings, we assessed the effect of droughts of on the vulnerability to cavitation in branches that develop during recovery. The newly formed branches displayed lower vulnerability to cavitation in the plants that underwent the severest droughts leading to native embolism; the pressure that induces 50% loss of conductance being of -3.98 MPa in severely droughted plants whereas it was of -3.1 MPa in control plants, respectively. Although unexpected, these results argue for an acclimation, and not a weakening, of this trait to drought events. Key messagesevere water stress make the future developed shoots less vulnerable to xylem cavitation.

plant biology↗

bioRxiv2019

Drought-induced mortality: stem diameter variation reveals a point of no return in lavender species

In the context of climate changes, water availability is expected to severely decline. Consequently, there is a need to predict mortality of woody species, especially to find a physiological threshold to drought-induced mortality. Lavender species (Lavandula angustifolia and Lavandula x intermedia) which are important crops of the Mediterranean region are affected by a decline, notably caused by successive intense drought events. Lavender response to extreme drought events was monitored using continuous stem diameter measurements. Water potential, stomatal conductance, loss of xylem hydraulic conductivity and electrolyte leakage were also measured during desiccation, and recovery was evaluated after rewatering. Two parameters computed from stem diameter variations were related to stress intensity and resilience to stress: PLD (Percentage Loss of Diameter) and stem PLRC (Percentage Loss of Rehydration Capacity of the stem), respectively. We showed that plants did not recover when the PLD reached its maximal value (PLDmax) which was 21.27 {+/-} 0.57% in both lavender species and whatever the growing conditions. This point of no return was associated with a high level of cell lysis evaluated by electrolyte leakage, and occurred far after the xylem hydraulic failure. We discussed the relevance of PLDmax as a threshold for drought-induced mortality and its physiological significance, in relation to the mortality mechanisms. One-sentence summaryUnder extreme drought, lavender death occurs when the water storage of the elastic compartment of the stem is exhausted.

plant biology↗