Efeitos da radiação ultravioleta-b sobre a morfisiologia de kappaphycus alvarezii (DOTY) doty ex P. Silva (gigartinales) variantes pigmentares verde e vermelha

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The effects of ultraviolet radiation in the biological relevant wavebands of UV-A (315#400 nm) and UV-B (280#315 nm) on algae have become an important issue as a man-made depletion of the protecting ozone layer has been reported. However, experimental designs to investigate this issue are manifold and the target organisms are extremely diverse. Data are included from the prokaryotic cyanobacteria, diatoms, brown algae, green algae and red algae. Including different habitats from marine littoral and open ocean to freshwater ponds, lakes and snow fields. A broad overview on UV effects on algae is given, with a focus on structurally visible changes. Kappaphycus alvarezii is a red macroalgae that presents several colors (red, brown, yellowish and green). It is natural from reef environments of the Indo-Pacific, China, Japan Islands of South East Asia, and East Africa region until Guam. This species was introduced in Brazil in the last decade, in São Paulo and Rio de Janeiro. This specie also currently being cultivated in the southern region of Brazil. It is of economical interest mainly due to the production of kappa carrageenans. This phycocolloids presents a great economical importance for food (milk and derived products, desserts and canned products), pharmaceutical, textile, and cosmetic industries because of its properties as thickener, emulsifier, stabilizer and gelling agent. The present investigation was undertaken to expand the knowledge of possible biological effects of UVBradiation in physiology, morphology and cellular organization of K. alvarezii green and red strains. Two strains (green and red) were grown to 24 C ( 2 C), photoperiod of 12h, photosynthetically active irradiance (PAR) was the day of 704 kJ/m- 2, sea water enriched with edium with 4 % of medium von Stosch and salinity of 34 ups. For the treatments were exposed to these variants RUVB for 3 h daily, irradiance of 1.2 kJ/m- 2 for 28 days. There was a decrease in growth rates in the two apical segments of the two strains exposed to RUVB. The morphology was also changed, with a winding in the distal portions of the stalk. The apical segment of the red variant showed necrosis and depigmentation of the process ends of the branches. The pigments change in concentrations after exposure to RUVB especially phycobiliproteins (FE, FC and AFC) where they showed decreases, while the concentration of Cla increased after exposure to RUVB. The strains in cross section, show the cortical region with a layer of small cells, the cells have more subcortical. These large cells have thick cell walls. The metachromatic with AT-O, on the walls of all cell types indicates the presence of carbohydrates acids. With the PAS reaction was intense in the cytoplasm of the cells of cortical and subcortical cells, marking the grains of starch. Meanwhile in cells exposed to the segments RUVB was a decrease in the number of grains of starch. The PAS positive cell walls indicate the presence of cellulose, which became more evident in the segments exposed to RUVB. CBB reacted cortical cells marking the cytoplasm and intercellular connections. SB with the reaction was more intense in the cuticle. The RUVB also caused changes in ultrastructure in cortical cells, with increasing thickness of the cell wall and change the contour cell. The destruction of the internal organization of the chloroplasts of the cells and cortical cells subcortical, along with the increase in the number of free ribosomes and plastoglobuli was observed. There was a reduction of intracellular spaces and formation of vesicles with concentric membranous bodies in the cytoplasm. However, the mitochondria, the cell nuclei and dictyosomes cortical and subcortical cells showed no ultrastructural alterations.

ASSUNTO(S)

botanica algas radiação ultravioleta pigmentos - avaliação

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