UVB radiation; a specific regulator of the growth and development of Arabidopsis thaliana
Research into the impacts of UVB radiation on plants and ecosystems began in the 1970’s in answer to concerns about the degradation of the stratospheric ozone layer. Early research focused solely on UVB as an agent of plant stress but recently the thinking surrounding UVB has undergone a paradigm shift, now it is seen as a key regulator of plant growth and development. The “UVB response” encompasses a multiplicity of changes in gene expression, metabolism and morphology. A thorough description of the range, complexities and interconnectedness of this response has only begun. The overall aim of this thesis was to explore the functional role the UVB response pathway and attempt to clarify some of the mechanisms behind these. This was achieved using Arabidopsis thaliana as a model system in both indoor and outdoor experiments. It was found that a plants ability to up regulate total soluble phenolics in response to a low dose UVB is potentially more important for UV-protection than accumulation of quercetins and kaempferols that are specifically glycosylated at C-7. Interestingly, the flavonoid glycosylation pattern affected plant morphology. Yet, one of the primary findings of this study was that the UVB induced changes in morphology were transitory. This study also demonstrated the role of UVB radiation and theUVB photoreceptor on morphology and biochemical make-up under changeable, complex, outdoor conditions. It was concluded that a functional UVB photoreceptor is required for optimized plant growth under natural UVB. Evidence of potential practical applications of UVB radiation within the protected cropping industry were also investigated using Lactuca sativa. Based on the findings it is proposed that key plant responses to UVB radiation may be exploitable in the context of improved crop quality and nutritional value.
Arabidopsis thaliana, UVB radiation, UVR8, Seasonality, Morphology, Flavonoids
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