The dynamic response of Arabidopsis thaliana to extreme environmental stressors

Overview

Plants have evolved to survive in moving fluids such as air and water (Vogel, 1981). As such, they experience fluctuating loads resulting from the fluid motion; often causing significant deformation to their rest configuration. Some deformations are beneficial (McCombe & Ackerman, 2018) while others can be detrimental (Gardiner, Berry, & Moulia, 2016). In any case, such large deformations are often outside the remit of standard engineering science/measurements, thus necessitating specialised techniques in their study (Gosselin, 2019).

Plants have developed a number of strategies to adapt to windy environments: (i) streamlining and reconfiguration, (ii) damping and wind-induced pruning (Lopez, Michelin, & De Langre, 2011) and (iii) pollen dehiscence (Timerman, Greene, Urzay, & Ackerman, 2014). In addition, the motion of their collectors affect particle capture in wind pollination (e.g., Phleum pratense) (McCombe & Ackerman, 2018). In general, however, the biological role of vibrations in plants is unclear. As the environment changes (wind pattern and intensity, drought etc.) due to climate change, we need to understand this fluid-structure interaction and how plants adapt to control it. This has impacts in the production of food and in our understanding of how plants adapt to their environment.

In this project, the student will perform a combined study focusing on both aerodynamic and biological aspects of plant adaptation to environmental conditions. They will explore how the resilience of different wild types and different mutants of Arabidopsis thaliana is affected by the changing climate. This project will use a dedicated ecophysiological wind tunnel to investigate the role that vortex-induced vibrations (VIV) play in the resilience of plants to a range of environmental stressors. In particular, the project will focus on how water deficiency affects lodging and mechanical properties between the different mutants of Arabidopsis thaliana.

Methodology

The student will work primarily with the University of Glasgow’s specialised wind tunnel for investigation of ecophysiological response of plants to the wind. Using specialised dynamical testing methods, developed in Glasgow, the mechanical properties of the plants exposed to different wind conditions (speed, intermittency) will be characterised. These measurements will be supplemented with kinematic tests of plants’ movements using high-speed imaging (for VIV analysis) and time-lapse imaging (for long-term and fatigue tests).

The student will also develop multiphysics numerical modelling tools (e.g., OpenFOAM, COMSOL, or Abaqus) to perform parametric studies of plants’ response to environmental stressors, and these numerical models will be validated against the empirical tests.

Project Timeline

Year 1

Literature review
1. Survey vibrational modes of plants.
2. Assemble database of VIV responses of plants and select different wild types and different mutants of Arabidopsis to be studied.
Experimental design
1. Develop basic designs of a test rig to measure dynamic response of plants to uniform airflow.
2. Perform calibration tests (natural frequency tests and modulus of elasticity etc.).

Year 2

Aerodynamic tests
1. Perform flow diagnostic tests to further calibrate the test rig.
2. Measure the effects of VIV with different configurations of plants and different levels of turbulence.

Year 3

Numerical modelling
1. Formulate mathematical model for plants’ vibrational response, and solve the model equations using numerical modelling tools.
2. Validate model using empirical tests.
3. Perform large parametric analysis to compile database of plants’ predicted response in extreme conditions.

Year 3.5

Write up and complete PhD thesis.

Training
& Skills

The student will receive significant training in force-measurement equipment and software packages required to analyse the results (e.g., MATLAB or Python). They will be trained in the fundamental aspects of fluid-structure interaction and state-of-the-art computational fluid dynamics software packages and multiphysics numerical modelling tools (OpenFOAM, Comsol, Abaqus, etc.). They will also develop skills in statistical analysis (the software package R) and interpretation of data and working with interdisciplinary teams. The student will be supported by the existing PhD students and postdocs based in investigators’ teams at Glasgow and Heriot-Watt Universities. This will create a superb environment to learn new skills and access the experience gained by their peers.

External training: During their project, the student will attend an international summer school on Plant Sciences (target: Plant Sciences Summer School at Zurich-Basel Plant Science Center). The student will also take part in an OpenFOAM training course at HLRS Stuttgart, Germany.

Dissemination of results: The student will learn to present their work at leading conferences such as the International Plant Biomechanics conference and the annual American Physical Society Division of Fluid Dynamics meeting (USA).

References & further reading

Gardiner, B., Berry, P., & Moulia, B. (2016). Review: Wind impacts on plant growth, mechanics and damage. Plant Science. https://doi.org/10.1016/j.plantsci.2016.01.006
Gosselin, F. P. (2019). Mechanics of a plant in fluid flow. Journal of Experimental Botany. https://doi.org/10.1093/jxb/erz288
Lopez, D., Michelin, S., & De Langre, E. (2011). Flow-induced pruning of branched systems and brittle reconfiguration. Journal of Theoretical Biology. https://doi.org/10.1016/j.jtbi.2011.06.027
McCombe, D., & Ackerman, J. D. (2018). Collector motion affects particle capture in physical models and in wind pollination. American Naturalist. https://doi.org/10.1086/697551
Timerman, D., Greene, D. F., Urzay, J., & Ackerman, J. D. (2014). Turbulence-induced resonance vibrations cause pollen release in wind-pollinated Plantago lanceolata L. (Plantaginaceae). Journal of the Royal Society Interface. https://doi.org/10.1098/rsif.2014.0866
Vogel, S. (1981). Life in moving fluids: the physical biology of flow. Princeton University Press.

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