Does ultraviolet radiation induce changes in the photophysiology and photochemistry of Halophila johnsonii Eiseman?

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Jennifer I. Kunzleman (Creator)
The University of North Carolina Wilmington (UNCW )
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Abstract: Halophila johnsonii is currently listed as threatened on the U.S. Endangered Species List due to its rarity within an extremely limited range of distribution. This species tends only to establish from the mid-intertidal down to 3 meters depth. Previous work has demonstrated that Halophila johnsonii, differing from its conspecific Halophila decipiens, exhibits high-light adapted photophysiology and contains a compound that absorbs maximally at 350 nm. Both of these characteristics were found to vary significantly following 4 days of acclimation during a reciprocal transplant experiment. Based on the plasticity of these photophysiological and photochemical responses, a controlled irradiance experiment was performed in an outdoor mesocosm utilizing the incident solar spectrum. Three different cut-off filters were used to measure the response of greenhouse-acclimated plants to PAR + UVA + UVB and PAR + UVA, versus PAR alone. Changes in photosynthetic efficiency were measured by pulse amplitude modulated (PAM) fluorometry. A newly-developed fluorometer, a UVA PAM, was used to monitor changes in UV protection. Variations in pigment characteristics such as UV absorbance, chlorophyll a and b, and total carotenoid concentrations were monitored over the course of the experiment in order to quantify both short- and long-term acclimation to different UV treatments. While significant changes in all parameters were observed within each of the treatments during the 21-day experiment, there were few differences among the three treatments. The factor that most influenced the physiological changes observed was the 2-fold increase in PAR that occurred when all experimental replicates were moved from the greenhouse to the outdoor mesocosms. The ability to acclimate with high tolerances to both UV irradiance and PAR may be a factor allowing Halophila johnsonii to exist intertidally while it appears to be competitively excluded subtidally. Perhaps the shallow intertidal exists as a refuge for this rare and protected species.

Additional Information

A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Endangered plants--Florida, Halophila--Florida, Plants--Effect of ultraviolet radiation on, Ultraviolet radiation--Physiological effect
Halophila -- Florida
Ultraviolet radiation -- Physiological effect
Plants -- Effect of ultraviolet radiation on
Endangered plants -- Florida

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