Quantifying vulnerability to embolism in tropical trees and lianas using five methods: can discrepancies be explained...

Area of Science:

• Plant physiology
• Hydraulic conductivity
• Drought stress response

Background:

• Vulnerability curves (VCs) are crucial for understanding plant water transport limitations under drought.
• Existing methods for constructing VCs have limitations and ongoing controversies regarding their accuracy.

Purpose of the Study:

• To compare the reliability of five methods (bench-top dehydration, air-injection-flow, pneumatic-air-discharge, optical, and X-ray-computed microtomography) for constructing VCs in tropical trees and lianas.
• To assess the influence of vessel traits on VC accuracy.
• To validate methods against direct embolism measurements.

Main Methods:

• Construction of VCs using bench-top dehydration (BD), air-injection-flow (AI), pneumatic-air-discharge (PAD), optical (OP), and X-ray-computed microtomography (MicroCT).
• Comparison of VCs generated by different methods.
• Analysis of vessel length and diameter effects.
• Validation against directly measured midday embolism.

Main Results:

• PAD and AI methods produced more vulnerable VCs, with PAD and AI overestimating embolism compared to direct measurements.
• BD, OP, and MicroCT methods yielded comparable, more resistant VCs and provided more accurate embolism estimations.
• Vessel length and diameter influenced the overestimation ratio for the AI method but not the PAD method.

Conclusions:

• The bench-top dehydration (BD), optical (OP), and X-ray-computed microtomography (MicroCT) methods are validated for constructing vulnerability curves in tropical plants.
• The pneumatic-air-discharge (PAD) and air-injection-flow (AI) methods require further mechanistic investigation due to potential inaccuracies.
• Caution is advised when using VCs from PAD and AI methods for estimating plant drought responses.