Dr. Sarah Verbeke, postdoctoral researcher at Ghent University (Belgium), visited the Institute of Natural Resources and Agrobiology of Seville (IRNAS-CSIC), Spain, for a Short-Term Scientific Mission (STSM) hosted by Dr. Virginia Hernández Santana. During her four-week stay from 31 August to 27 September 2026, she focused on evaluating the stress-relaxation method as a tool to quantify cell wall mechanical properties in olive leaves.
Understanding how cell wall properties regulate leaf growth remains a major challenge in plant physiology. Two key factors controlling irreversible cell expansion are cell wall extensibility and the yield threshold, yet obtaining reliable measurements of these properties remains technically challenging. The main objective of the STSM was therefore to assess a methodology for quantifying these parameters in olive leaves using pressure-relaxation measurements.
The experimental work focused on establishing a robust protocol for collecting and analysing relaxation curves. Measurements performed on actively growing olive leaves produced relaxation patterns consistent with plant growth theory, while curve fitting yielded realistic estimates of cell wall extensibility and yield threshold. This resulted in a practical protocol that can now be further tested across different species, growth stages, and environmental conditions. Although additional validation is still required, the method shows considerable promise as a rapid and accessible approach for determining key cell wall properties involved in plant growth.
In parallel, a modelling framework was developed to automate the calibration of a Lockhart-based growth model. The framework combines sensitivity analysis, parameter identifiability assessment, automated parameter selection, and model calibration, enabling the efficient extraction of growth-related parameters from experimental datasets. Together, the experimental protocol and modelling tools developed during the STSM provide new opportunities to quantify cell wall mechanical properties and incorporate them into mechanistic plant growth models. These developments contribute directly to the objectives of FruitCREWS by improving the measurement and modelling of growth processes in perennial crops.