Alice Gauthey

Candidature

PhD Candidate

Thesis title

Non-Invasive Imaging of Drought-Induced Cavitation in Plants

Research Project

Climate change is predicted to increase the intensity and recurrence of extreme climate events such as drought. Drought-induced mortality can have important impacts on species distributions and forest community composition, causing both ecological and economic issues. Therefore, it is essential to be able to understand drought susceptibility via plant hydraulics so we can predict the physiological thresholds that initiate tree mortality.

This thesis will investigate how different plant species respond to drought and attempt to answer some key physiological questions linked to recovery after a severe water loss. Specifically, this thesis aims to address the following questions:

  1. How to reliably measure plant’s vulnerability to drought? The traditional methods to quantify the degree of impact (i.e. embolism) require cutting plant material (stems, roots, or leaves), which causes artefacts by perturbing the vascular system before measurement. However, in the last two decades, advances in imaging technologies have allowed for the development of new techniques. This chapter is focused on comparing these destructive (bench dehydration and flow-centrifuge) and non-invasive methods (micro computed-tomography and optical vulnerability technique).
  2. Is embolism refilling a common strategy across plants species to recover after an intense drought event? In order to transport water from the roots to the shoots, the vascular system (i.e. xylem) is under negative pressure which can be compared to a tension. As the water stress becomes more important, the tension increase and bubbles of gas are formed inside the xylem. This chapter’s goal is to understand if refilling of gas-filled vessels is possible under decreased negative pressure.
  3. Application of imaging techniques to understand a massive dieback event in the mangrove forests of Queensland. During the summer 2015-16, a massive dieback affected mangroves community in the North of Australia. Along the whole gulf of Carpentaria, more than 1000km of shoreline suffered from this severe mortality. The aim of this chapter is to evaluate physiological trait of mangroves in the Gulf of Carpentaria and in the coast of Queensland in order to measure their capacity to recover, the potential or adaptive plasticity and the physiological threshold of survival.
Supervisors

A/Professor Brendan Choat, Professor Belinda Medlyn, Professor David Tissue