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Journal Article

Variation in xylem structure and function in stems and roots of trees to 20 m depth

Authors: McElrone, AJ, WT Pockman, J Martinez-Vilalta, RB Jackson

To assess hydraulic architecture and limitations to water transport across whole trees, we compared xylem anatomy, vulnerability to cavitation (Y50), and specific hydraulic conductivity (Ks) of stems, shallow roots, and deep roots (from caves to 20 m depth) for four species: Juniperus ashei, Bumelia lanuginosa, Quercus fusiformis and Quercus sinuata. Mean, maximum, and hydraulically-weighted (Dh) conduit diameters and Ks were largest in deep roots, intermediate in shallow roots, and smallest in stems (P<0.05 for each). Mean vessel diameters of deep roots were 2.1 to 4.2 fold greater than in stems, and Ks was 7 to 38 times larger in the deep roots. Y50 also increased from stems to roots with depth, as much as 24 fold from stems to deep roots in B. lanuginosa. For all species together, Y50 was positively correlated with both Dh and Ks, suggesting a potential tradeoff exists between conducting efficiency and safety. The anatomical and hydraulic differences documented here suggest that the structure of deep roots minimizes flow resistance and maximizes deep water uptake.

See also commentary by Gretchen North (New Phytologist 163: 447-449) np04north.pdf
Journal Name
New Phytologist
Publication Date