Stomata are microscopic pores composed of two guard cells that open and close to regulate the movement of gasses, mainly H2O vapour and CO2, into and out of leaf tissue. They allow plants to regulate transpirational water loss and photosynthetic carbon assimilation in response to changes to their environment. As well as playing an important role for plants on an individual level, the function of stomata affects global hydrological and carbon cycles. Stomata are sensitive to many signals including water availability, temperature, CO2 and light, and have developed complex signalling networks that allow for the integration of these signals. This thesis investigates the signalling mechanisms behind stomatal responses to darkness. The mechanisms underlying dark-induced stomatal closure are poorly understood in comparison to other closure inducing signals such as the phytohormone abscisic acid (ABA), known for its role in plant drought responses. This thesis examines the role of ABA signalling in stomatal responses to darkness. ABA signalling has previously been linked to stomatal responses to darkness, however its exact role is unclear. This thesis shows that ABA signalling is not essential for dark-induced stomatal closure, however mutations within ABA metabolic and signalling machinery do affect stomatal response speeds to darkness and light. Additionally, this thesis investigates the longer-term effects of darkness on ABA signalling and metabolism transcript dynamics. Here, darkness is found to specifically upregulate a subset of ABA receptor transcripts. Exploring a physiological role for dark induced ABA receptor upregulation, the effect of daylength on the stomatal development of various ABA signalling and metabolism mutants is analysed. This thesis also explores the roles of a plant cGMP activated kinase (protein kinase G/PKG) in regulating stomatal movements. Here, evidence is provided showing a role for PKG in dark-induced stomatal closure, furthermore, suggesting a role for cGMP signalling in this process.
|Date of Award||24 Jun 2021|
- The University of Bristol
|Supervisor||Alistair M Hetherington (Supervisor) & Antony Dodd (Supervisor)|