Hydraulic vulnerability segmentation in compound-leaved trees: Evidence from an embolism visualization technique. Issue 1 (31st January 2022)

• Record Type: Journal Article
• Authors: Song, Jia; Trueba, Santiago; Yin, Xiao-Han; Cao, Kun-Fang; Brodribb, Timothy J; Hao, Guang-You
• Is Part Of: Plant physiology. Volume 189:Issue 1(2022)
• Page Start: 204
• Page End: 214
• Publication Date: 2022-01-31
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1093/plphys/kiac034
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract: The hydraulic vulnerability segmentation (HVS) hypothesis implies the existence of differences in embolism resistance between plant organs along the xylem pathway and has been suggested as an adaptation allowing the differential preservation of more resource-rich tissues during drought stress. Compound leaves in trees are considered a low-cost means of increasing leaf area and may thus be expected to show evidence of strong HVS, given the tendency of compound-leaved tree species to shed their leaf units during drought. However, the existence and role of HVS in compound-leaved tree species during drought remain uncertain. We used an optical visualization technique to estimate embolism occurrence in stems, petioles, and leaflets of shoots in two compound-leaved tree species, Manchurian ash ( Fraxinus mandshurica ) and Manchurian walnut ( Juglans mandshurica ). We found higher (less negative) water potentials corresponding to 50% loss of conductivity ( P 50 ) in leaflets and petioles than in stems in both species. Overall, we observed a consistent pattern of stem > petiole > leaflet in terms of xylem resistance to embolism and hydraulic safety margins (i.e. the difference between mid-day water potential and P 50 ). The coordinated variation in embolism vulnerability between organs suggests that during drought conditions, trees benefit from early embolism and subsequent shedding of more expendable organs such as leaflets and petioles, as this provides a degree of protection to the integrity of the hydraulic system of the more carbon costly stems. Our results highlight the importance of HVS as an adaptive mechanism of compound-leaved trees to withstand drought stress. Abstract : The long-proposed hypothesis that more terminal organs have greater vulnerability to drought-induced embolism was tested and proved in shoots of compound-leaved trees using an optical technique.