A higher tissue fraction of parenchyma in secondary xylem supports growth recovery of angiosperm trees after drought

Resilience to drought represents an important focus for trees during
climate change, with the aim of predicting the resistance and recovery of
species worldwide. Previous studies mainly linked tree growth resilience
to plant functional traits that are related to resource acquisition and
investment. Here, we investigate a potential link between resilience and
the amount of parenchyma tissue in wood, a multifunctional tissue that may
provide various physiological benefits to drought-related mechanisms. We
compiled a global tree-ring dataset to evaluate the relationship between
growth resistance, resilience or recovery from drought, and xylem
parenchyma tissue fractions of fifty angiosperms, which was complemented
with a local study of 9 species from Mt. Tiantong in China. We also
assessed the influence of climate and phylogeny on these relationships. We
found that growth recovery after drought was positively related to the
fractions of total parenchyma locally and globally. This association
remained statistically significant when accounting for the effects of
climate and phylogeny. No other associations between parenchyma fractions
and growth resilience metrics were statistically significant. Our results
suggest that drought recovery of angiosperm trees is affected by the
amount of parenchyma. Incorporating xylem parenchyma fraction with other
traits, such as hydraulic traits, could therefore enhance our
comprehension of how various angiosperm tree species will respond to
future droughts. Further studies should focus on unraveling the
physiological roles of xylem parenchyma fraction.