Physiological and Morphological Responses to Drought Stress in Different Cultivation Environments in Wild Type and ABA-deficient Barley

Abstract

Global food security is increasingly threatened by the effects of climate change. Of the environmental factors affected by climate change, drought is one of the most critical for plant survival and reproduction, shaping plant morphology and physiology and therefore crop productivity. Although the effects of drought on plants are widely studied, studies are often conducted in controlled greenhouse or laboratory conditions rather than more realistic field-like conditions. This is justified by the lower costs, convenience, and ability to disentangle the effects of different factors in more controlled conditions. This thesis explores the effect of the same watering limitations in different cultivation environments -greenhouse, outside container, and raised bed - on Hordeum vulgare (spring barley) growth and physiology to assess the translatability of the same applied drought treatment. Additionally, as plants in the field often experience multiple stresses simultaneously, I investigate the interaction between drought stress in spring barley and herbivory by the sap-sucking aphid herbivore Rhopalosiphum padi and the chewing mollusc herbivore Cornu aspersum. I particularly focus on the role of abscisic acid (ABA), a key phytohormone in plant-stress responses, in coordinating plant responses to these stresses in different cultivation environments through the use of the ABA-deficient spring barley mutant Az34.
The results of this thesis demonstrate that the same applied drought treatment resulted in different plant growth and physiological responses in greenhouse conditions compared to simulated field conditions. Results also indicate that the effect of drought on aphid performance on barley, as well as barley response to aphid herbivory differs between cultivation environments. In controlled conditions, experiments suggested that barley may be more susceptible to both sap-sucking and chewing herbivores in drought conditions compared to control. Az34 barley did not show a consistent decrease in ABA concentration under stress conditions relative to Wild Type barley, therefore the role of ABA in responses to drought stress and herbivory were not able to be determined.
Together, this thesis demonstrates the importance of studying plant-stress interactions in realistic field-like conditions in order to produce results that are more translatable to agricultural systems. Accurate assessments of how plants respond to climate change-related stresses and their interactions is becoming increasingly important for shaping effective crop management strategies and ensuring food security under future climate scenarios.

Date of Award	2026
Original language	English
Awarding Institution	University of Plymouth
Supervisor	Anne Plessis (Director of Studies (First Supervisor)), James Buckley (Other Supervisor), Mick Hanley (Other Supervisor), Michael Wilde (Other Supervisor) & Nicholas Smirnoff (Other Supervisor)