Date of Award

5-2020

Document Type

Thesis campus only

Department

Biology

First Advisor

James R. Shinkle

Second Advisor

Kelly G. Lyons

Third Advisor

Paul W. Barnes

Abstract

Plants are routinely exposed to UV-B radiation (280-315 nm) as a natural component of incident solar radiation. As in other organisms, UV-B radiation is relevant to plants as both a source of damage and photomorphogenic cue. Previous studies have indicated that shortwave UV-B radiation (280-300 nm) elicits unique responses in model plants under laboratory conditions. In this study, we examine how shortwave UV-B radiation combined with other environmental variables such as microclimate, seasonality, circadian rhythms, and transient weather conditions impact the pigmentation and morphology of C3 shade-adapted inland sea oats (Chasmanthium latifolium) and C4 sun-adapted side-oats grama (Bouteloua curtipendula). We characterized the responses of these grasses to shortwave UV-B radiation in a field environment by placing greenhouse-grown, UV-naive individuals under shortwave UV-B excluding or transmitting filters in three field sites along an elevational and urban-rural gradient across Central Texas and measure their responses through dry biomass, leaf pigment extract absorbance, leaf surface reflectance, and chlorophyll and flavonoid content. We found that while both C. latifolium and B. curtipendula adjust their pigmentation and morphology in response to exposure to a field environment, these only some of these changes are a result of exposure to shortwave UV-B radiation and many other environmental variables also impact the UV-B associated responses of these plants. This result indicates that shortwave UV-B radiation is relevant to plant UV-B associated responses in a field environment and reinforces the importance of studying plant responses to UV-B radiation under realistic lighting conditions, an understanding of which is crucial to forecasting how the ecosystems of the future will respond to climate change and atmospheric ozone fluctuation.

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