Effect of nitrate concentration and UVR on photosynthesis,respiration, nitrate reductase activity,and phenolic compounds in <Emphasis Type="Italic">Ulva rigida</Emphasis> (Chlorophyta) |
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Authors: | Email author" target="_blank">Alejandro?Cabello-PasiniEmail author Víctor?Macías-Carranza Roberto?Abdala Nathalie?Korbee Félix?L?Figueroa |
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Institution: | 1.Instituto de Investigaciones Oceanológicas,Universidad Autónoma de Baja California,Ensenada,Mexico;2.Departamento de Ecología, Facultad de Ciencias,Universidad de Málaga, Campus Universitario Teatinos,Málaga,Spain |
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Abstract: | Seaweeds growing in the intertidal zone are exposed to fluctuating nitrate and ultraviolet radiation (UVR) levels. While it
has been shown that elevated UVR levels and the decrease of nitrate concentration can reduce photosynthetic levels in seaweeds,
less is known about the combined effect of nitrate levels and UVR on metabolism and photoprotection mechanisms of intertidal
species. Consequently, the objective of this study was to evaluate the effect of nitrate concentration and UVR treatments
on photosynthesis, respiration, nitrate reductase activity and phenolic compound levels of Ulva rigida (Chlorophyta). There was a two- to threefold increase in maximal gross photosynthesis (GPmax) and respiration rates, as nitrate increased from 0 to 50 μM NO3−. Similarly, nitrate reductase activity increased linearly from low values in algae incubated at 0 μM NO3 to high values in tissue incubated at 50 μM NO3−. Phenolic compounds in the tissue of U. rigida increased approximately 60% under 50 μM NO3− relative to those incubated at 0 μM NO3−. Algae exposed to UVR (8 h) showed a significant decrease in the effective quantum yield and respiration, however, no effect
was observed in the phenolic compounds levels. Full recovery of effective quantum yield was observed after U. rigida was transferred for 48 h to low PAR. Nitrate reductase also decreased after an 8-h UVR exposure, but no differences were
observed among the nitrate treatments. This study shows that high nitrate levels reduced the negative effect of UVR on the
effective quantum yield and increased the recovery of key metabolic enzymes. It is possible that the increase of phenolic
compounds in the thallus of U. rigida under high nitrate levels provide a photoprotective mechanism when exposed to high UV levels during low tides. |
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