Excising stem samples underwater at native tension does not induce xylem cavitation

Area of Science:

• Plant physiology
• Drought tolerance mechanisms
• Xylem hydraulics

Background:

• Xylem cavitation, a key factor in plant drought tolerance, is measured by percentage loss of conductivity (PLC).
• A recent hypothesis suggested that sample preparation under tension could artificially inflate PLC measurements, termed the 'tension-cutting artefact'.
• This artefact could compromise accurate assessments of plant water stress responses.

Purpose of the Study:

• To test the validity of the hypothesized 'tension-cutting artefact' on xylem cavitation measurements.
• To determine if sample preparation under tension significantly affects percentage loss of conductivity (PLC) values.
• To validate existing methods for assessing plant drought tolerance.

Main Methods:

• Xylem cavitation (PLC) was measured on five plant species under native tension and after tension relaxation.
• Percentage loss of conductivity was compared between native and relaxed samples to identify any tension-induced artefacts.
• A specific sample preparation technique involving trimming was employed to avoid potential artefacts.

Main Results:

• The tension-cutting artefact hypothesis was not supported in four out of five species tested.
• No significant differences in PLC were observed between native and relaxed xylem samples in most species.
• Observed differences in one species (Laurus nobilis) were attributed to vessel refilling, not the tension-cutting artefact.

Conclusions:

• The 'tension-cutting artefact' does not appear to be a significant confounding factor in standard xylem cavitation measurements.
• Current methods for assessing plant drought tolerance via PLC measurements are likely reliable.
• Careful sample preparation, including trimming, can further ensure the accuracy of cavitation assessments.