No stress memory pattern was detected in sugar maple and white spruce seedlings subjected to experimental droughts

An increase in the frequency and magnitude of drought events threatens the health of forests and the economic, ecological, and societal services they provide. It has been widely demonstrated that trees undergoing a succession of stresses may accumulate lesions that in turn lead to a decrease in their vigor and eventually to death. However, recent studies have shown that a nonlethal stress should also initiate a stress memory, which triggers a faster and stronger plant defensive response when a new stress occurs. Although this mechanism is well understood in many herbaceous plants, a better understanding in trees is needed. The aim of our study was to explore the capacity of two forest tree species to develop a stress memory. A greenhouse experiment was conducted to evaluate the tree seedlings' vigor after one or two consecutive droughts separate from a rehydration period during the same growing season. No stress memory pattern was observed for the two tree species as, on the contrary, we even observed a stress accumulation pattern in sugar maple. It remains possible that some individuals in our study developed stress memory, but that we were not able to detect it. The fine-tuning of experimental parameters and the conducting of longitudinal studies would be helpful to detect individual capacity in stress memory activation.

Automated summary

The increase in drought events threatens forests and the services they provide. Trees accumulating lesions from successive stresses can lead to decreased vigor and death. Nonlethal stress may initiate a stress memory, triggering a stronger defensive response. While well understood in herbaceous plants, this mechanism needs further understanding in trees. This study aims to explore stress memory development in two forest tree species.