Investigating the effects of UV-B and temperature on survival and stomatal physiology in Arabidopsis thaliana seedlings

Abstract

Low fluence rate UV-B, perceived by the UV RESISTANCE LOCU 8 (UVR8) photoreceptor is an important environmental signal which affects plant development and growth via its effects on gene expression and plant physiology. Common plant responses to UV-B include inhibition of hypocotyl and petiole elongation, alterations to leaf size, the production of epidermal pigments and the generation of reactive oxygen species (ROS). This thesis investigates the effects of UV-B and temperature on survival and stomatal physiology in Arabidopsis thaliana. High and low temperatures are highly stressful to plants and cause great economic losses each year. There is some evidence that UV-B can protect plants against excessive heat and cold, but the response in Arabidopsis is poorly understood. In this thesis, no significant enhancement of Arabidopsis cold acclimation, basal thermotolerance or acquired thermotolerance was observed with UV-B supplementation. A potential indirect role for UV-B in cold acclimation was, however, identified via flavonoid production. This thesis further investigates the effects of low fluence UV-B on Radish Leaf development in a vertical aeroponic system in collaboration with the iCASE partner, LettUs Grow. Vertical farms use artificial light or a mixture of artificial and natural light. This means that growing plants are exposed to no, or very little UV-B. This thesis used the fast-growing microherb Radish Leaf to investigate the applicability of UV-B in a vertical farm system and its effects on plant development, pigment accumulation and antioxidant capacity. Low dose UV-B supplementation increase flavonol accumulation and antioxidant capacity, without negatively impacting plant growth and biomass. The effects of low fluence UV-B on stomatal apertures of Arabidopsis cotyledons were investigated. High fluence rate UV-B has been shown to close stomata in isolated epidermal peels of mature Arabidopsis, but the effect of UV-B on cotyledon stomata has not been established. This thesis shows that low dose UV-B, perceived by UVR8 opens stomata in a response requiring PHYTOCHROME INTERACTING FACTOR (PIF) transcription factors, auxin and ABA signalling.

Date of Award	20 Jun 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Keara A Franklin (Supervisor) & Alistair Hetherington (Supervisor)