Response of the agarophyte Gelidium floridanum after in vitro exposure to ultraviolet radiation B: changes in ultrastructure, pigments, and antioxidant systems |
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Authors: | éder C Schmidt Rodrigo W dos Santos Caroline de Faveri Paulo A Horta Roberta de Paula Martins Alexandra Latini Fernanda Ramlov Marcelo Maraschin Zenilda L Bouzon |
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Institution: | 1. Post-Graduate Program in Cell Biology and Development, Department of Cell Biology, Embryology and Genetics, Federal University of Santa Catarina, CP 476, 88049-900, Florianópolis, Santa Catarina, Brazil 2. Macroalgae Laboratory, Department of Cell Biology, Embryology and Genetics, Federal University of Santa Catarina, CP 476, 88049-900, Florianópolis, Santa Catarina, Brazil 3. Department of Botany, Federal University of Santa Catarina, CP 476, 88010-970, Florianópolis, Santa Catarina, Brazil 4. Laboratório de Bioenergética e Estresse Oxidativo, Department of Biochemistry, Federal University of Santa Catarina, CP 476, 88049-900, Florianópolis, Santa Catarina, Brazil 5. Plant Morphogenesis and Biochemistry Laboratory, Federal University of Santa Catarina, CP 476, 88049-900, Florianópolis, Santa Catarina, Brazil 6. Central Laboratory of Electron Microscopy, Federal University of Santa Catarina, CP 476, 88049-900, Florianópolis, Santa Catarina, Brazil
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Abstract: | As a source of agar, the red macroalga Gelidium floridanum is a seaweed of great economic importance. However, it grows in a region exposed to high ultraviolet B radiation (UVBR). Therefore, to study the in vitro effect of UVBR on this plant, apical segments of G. floridanum were cultivated and exposed to photosynthetically active radiation (PAR) at 80?μmol photons m?2?s?1 and PAR + UVBR at 1.6?W?m?2 at 3?h per day for 7?days. The samples were processed for electron microscopy, and agar yield, growth rates, mitochondrial activity, protein levels, chlorophyll a, phycobiliproteins, carotenoids and phenolic compounds, and photosynthetic performance were examined. After 7?days of exposure to PAR + UVBR, G. floridanum experienced ultrastructural damage that was primarily observed in the internal organization of chloroplasts, increased cell wall thickness, as well as increased volume of plastoglobuli and free ribosomes. Moreover, this exposure might have caused photodamage and photoinhibition of photosynthetic pigments (chlorophyll a and phycobiliproteins), leading to a decrease in photosynthetic efficiency, relative electron transport rate, and maximum photosynthetic rate. These phenomena were matched with a corresponding decrease in growth rates and depigmentation, combined with partial necrosis of the apical segments exposed to PAR + UVBR. Additionally, the UVBR-induced damage elicited a marked cellular antioxidant response, possibly as a consequence of free radical generation. |
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