Affiliation:
1. School of Natural Sciences University of Tasmania Private Bag 55 Hobart TAS 7001 Australia
2. School of the Environment Yale University New Haven CT 06520 USA
Abstract
Summary
Resolving the position of roots in the whole‐plant hierarchy of drought‐induced xylem embolism resistance is fundamental for predicting when species become isolated from soil water resources. Published research generally suggests that roots are the most vulnerable organ of the plant vascular system, although estimates vary significantly. However, our knowledge of root embolism excludes the fine roots (< 2 mm diameter) that form the bulk of total absorptive surface area of the root network for water and nutrient uptake.
We measured fine root and stem xylem vulnerability in 10 vascular plant species from the major land plant clades (five angiosperms, three conifers, a fern and lycophyte), using standardised in situ methods (Optical Methods and MicroCT).
Mean fine root embolism resistance across the network matched or exceeded stems in all study species. In six of these species (one fern, one lycophyte, three conifers and one angiosperm), fine roots were significantly more embolism resistant than stems. No clear relationship was found between root xylem conduit diameter and vulnerability.
These results provide insight into the resistance of the plant hydraulic pathway at the site of water and nutrient uptake, and challenge the long‐standing assumption that fine roots are more vulnerable than stems.
Funder
Australian Research Council Centre of Excellence for Plant Success in Nature and Agriculture