Loss of transmittance in leaves: a new way to approach cell death dynamic
Résumé
Predictions from global climate models indicate a forthcoming escalation in the frequency and severity of drought events. These events have already demonstrated significant consequences on the survival of trees. Understanding how the future climate is impacting the survival of plant cells, and thus plant’s survival, is a key challenge nowadays. Most of the actual methods, like electrolytes leakage, are destructive and time-consuming. Finding a new, more rapid and non-destructive approach to assess cell death dynamics appears as a necessary step at a time where new studies consist of large-scale studies at the ecosystem level. The optical method, which has been used on leaves for several years to generate the species vulnerability curve, has highlighted the existence of changes in transmittance in different areas of the leaves, particularly at the vein level. These changes in transmittance at the leaf veins level are currently being used to generate the vulnerability curve. However, recent studies have pointed out that changes in transmittance were also noticeable in the lamina of the leaves. Taking into account those recent observations, our study aims to explore the link between the loss in light transmittance at the whole leaf level and their cellular mortality. For this, trees presenting various xylem vulnerability to cavitation were exposed to a severe drought and their leaf water potential was monitored. On the leaves used for water potential assessment, we quantified the extent of leaf cell mortality by applying electrolyte leakage methodology. Cavicams were installed on two leaves per tree and took pictures every five minutes to track the loss in transmittance in leaf veins and leaf lamina. Our results show that in five species, A. grandiflora, Q.ilex, L. nobilis, E. viminalis and P. tremula x alba, the loss of transmittance of the leaf lamina undergoing severe drought follows the dynamic of cellular mortality and could thus be a good indicator of the dynamics of cellular mortality in leaves.