Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation hypothesis
Article first published online: 23 MAY 2014
© 2014 The Authors. New Phytologist © 2014 New Phytologist Trust
Volume 203, Issue 3, pages 842–850, August 2014
How to Cite
Pivovaroff, A. L., Sack, L. and Santiago, L. S. (2014), Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation hypothesis. New Phytologist, 203: 842–850. doi: 10.1111/nph.12850
- Issue published online: 10 JUL 2014
- Article first published online: 23 MAY 2014
- Manuscript Accepted: 16 APR 2014
- Manuscript Received: 30 JAN 2014
- National Science Foundation (NSF). Grant Numbers: DGE-1326120, 08-17212
- hydraulic conductance;
- hydraulic safety margin;
- leaf mass per area;
- Mediterranean-type ecosystem;
- water potentials;
- wood density
- Coordination of water movement among plant organs is important for understanding plant water use strategies. The hydraulic segmentation hypothesis (HSH) proposes that hydraulic conductance in shorter lived, ‘expendable’ organs such as leaves and longer lived, more ‘expensive’ organs such as stems may be decoupled, with resistance in leaves acting as a bottleneck or ‘safety valve’.
- We tested the HSH in woody species from a Mediterranean-type ecosystem by measuring leaf hydraulic conductance (Kleaf) and stem hydraulic conductivity (KS). We also investigated whether leaves function as safety valves by relating Kleaf and the hydraulic safety margin (stem water potential minus the water potential at which 50% of conductivity is lost (Ψstem − Ψ50)). We also examined related plant traits including the operating range of water potentials, wood density, leaf mass per area, and leaf area to sapwood area ratio to provide insight into whole-plant water use strategies.
- For hydrated shoots, Kleaf was negatively correlated with KS, supporting the HSH. Additionally, Kleaf was positively correlated with the hydraulic safety margin and negatively correlated with the leaf area to sapwood area ratio.
- Consistent with the HSH, our data indicate that leaves may act as control valves for species with high KS, or a low safety margin. This critical role of leaves appears to contribute importantly to plant ecological specialization in a drought-prone environment.