talijanski

Adattamento della macroalga rossa Gracilaria longa allo stress da cadmio: risposte fisiologiche, biochimiche ed ultrastrutturali

It is well known that heavy metals play a significant role in environmental pollution and cadmium is one of the most important toxicans. There are many studies on microalge but only a few on macroalge although they are considered as valuable indicators because of their accumulation capacity. The effects of cadmium on the fine structure of the vegetative cells of the red alga Gracilaria longa were studied under laboratory cultured conditions. The red alga thalli were exposed to 900 µ M Cd2+, 1200 µ M Cd2+and 1500 µ M Cd2+ concentration for 5 days by adding cadmium nitrate to the culture medium. Ultrastructural modifications due to cadmium ad/absorption were observed by TEM/SEM electron microscopy. Microscopy studies showed striking changes in the plasmalemma of treated algae, which became irregular and convoluted. Numerous electron transparent exocytic vesicles, possibly related to cell wall polysaccharide synthesis, were observed. The appearance of ribosomes and Golgi bodies, not significantly present in the cytoplasms of untreated cells, suggested enhanced protein and carbohydrate biosynthesis. The cell walls became smooth and thick. Electron-dense spheroids occurred in the plasmalemma-cell wall interface, on the cell wall itself and in nearby vesicular membrane system. Many small vacuoles containing large metal complexes were formed. Conducted analyses indicate large adaptability to a considerable range of biotic and abiotic factors, while bioaccumulation capability of this species enables its use as a biofilter in various conditions of heavy metal pollution.

red macrophyte; heavy metals; stress; ultrastructure; cadmium; Gracilaria longa

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