Exploring within-plant hydraulic trait variation: A test of the vulnerability segmentation hypothesis

Area of Science:

• Plant physiology
• Ecology
• Biophysics

Background:

• Vulnerability segmentation, the differential susceptibility of plant tissues to drought-induced embolism, varies significantly across species and environments.
• Observed patterns include conventional (stem < leaf), no segmentation, and reverse (stem > leaf) vulnerability segmentation.

Purpose of the Study:

• To develop a hydraulic model to test hypotheses regarding vulnerability segmentation.
• To investigate how vulnerability segmentation interacts with other plant traits to influence plant conductance.

Main Methods:

• A hydraulic model was developed and tested across a wide parameter space.
• Experiments included a case study of two species with contrasting vulnerability segmentation: Quercus douglasii and Populus trichocarpa.

Main Results:

• Conventional vulnerability segmentation effectively preserves stem conductance.
• Reverse vulnerability segmentation can enhance conductance across the entire stem-leaf hydraulic pathway, especially with vulnerable xylem and high leaf resistance.

Conclusions:

• The impact of vulnerability segmentation is contingent on other plant traits, particularly hydraulic segmentation.
• These findings offer a framework for interpreting variable observations of vulnerability segmentation in plants.