Lag in gas exchange recovery following natural drought associated with embolism formation

R.P. Skelton, T.J. Brodribb
Although drought-related damage thresholds to plant species and post-drought recovery of forest productivity are not yet fully understood, recent findings suggest that post-drought recovery of gas exchange can be predicted by xylem safety margins and loss of whole plant hydraulic conductance. Consequently, understanding the causes of declines in leaf xylem hydraulic conductance (kleaf) has important implications for predicting lags in recovery of gas exchange following drought. Here we investigated whether lags in recovery of gas exchange caused by loss of kleaf were associated with embolism in xylem. During a natural drought event, we used miniature external sapflow technology to understand dynamic in situ plant water use in a cohort of leaves in a woody tree species, Acacia mearnsii De Wild. (Fabaceae). We also investigated the relationship between loss of kleaf quantified using the rehydration kinetics method and the formation of embolism in shoot xylem using the recently developed optical vulnerability method. Our findings indicated that a lag in gas exchange recovery following rehydration after drought exposure was associated with loss of kleaf. A direct relationship between the extent of embolism formation and loss of kleaf suggests that declines in kleaf in A. mearnsii might be caused by xylem embolism formation. Although the exact causal relationship is not clear, these data support the idea that xylem vulnerability to embolism induced by water deficit can be useful for obtaining thresholds of loss of function, and drought tolerance in woody plant species.
Skelton, R.P. and Brodribb, T.J. (2018). Lag in gas exchange recovery following natural drought associated with embolism formation. Acta Hortic. 1222, 49-58
DOI: 10.17660/ActaHortic.2018.1222.8
sapflow, leaf xylem hydraulic conductance, xylem embolism, kleaf

Acta Horticulturae