Convergent tapering of xylem conduits in different woody species
Article first published online: 9 NOV 2005
Volume 169, Issue 2, pages 279–290, February 2006
How to Cite
Anfodillo, T., Carraro, V., Carrer, M., Fior, C. and Rossi, S. (2006), Convergent tapering of xylem conduits in different woody species. New Phytologist, 169: 279–290. doi: 10.1111/j.1469-8137.2005.01587.x
- Issue published online: 9 NOV 2005
- Article first published online: 9 NOV 2005
- Received: 3 August 2005 Accepted: 7 September 2005
- hydraulic constraints;
- tree height;
- xylem conduits
- • A recent theoretical model (the West, Brown and Enquist, WBE model) hypothesized that plants have evolved a network of xylem conduits with a tapered structure (narrower conduits distally) which should minimize the cost of water transport from roots to leaves. Specific measurements are required to test the model predictions.
- • We sampled both angiosperms and gymnosperms (50 trees) growing in different environments with heights ranging from 0.5 to 44.4 m, measuring variations of the xylem–conduit diameter from tree top to stem base.
- • In all trees measured, mean hydraulically weighted conduit diameters (Dh) at the tree top were narrower than those at the stem base. In actively growing trees, the longitudinal variation of Dh showed a degree of tapering in agreement with WBE predictions, while trees close to their maximum height showed slightly lower conduit tapering. Comparing different species, a very good correlation was observed between degree of xylem tapering and tree height (r2 = 0.88; P < 0.0001) independently of any other variable (age, site, altitude, etc.).
- • As predicted by WBE, sampled trees seemed to converge towards similar xylem conduit tapering. However, trees approaching their maximum height had a nonoptimal tapering which appeared insufficient to compensate for the progressive increase in tree height.