Cellular and biochemical alterations induced by diesel oil in the brown alga Sargassum cymosum var. stenophyllum cultured in vitro.

The effect of the in vitro acute exposure to diesel oil (0.001%, 0.01%, 0.1%, and 1%, v/v) has been evaluated in the brown seaweed Sargassum cymosum var. stenoplhyllum by determining the contents of photosynthetic pigments, phenolic compounds, and morphological and cellular changes. In vitro cultures of S. cymosum were exposed to diesel oil for 30min, 1h, 12h, and 24h under laboratory-controlled conditions. Chlorophyll a and c contents increased after diesel oil exposure as the amounts of carotenoids did not show a clear trend along the experimental period. However, a reduction in the concentration of phenolic compounds was detected by chemical analysis, a finding further corroborated by electron microscopy and cytochemical analyzes. The thickness of the cell wall showed to be augmented and the accumulation of phenolic compounds therein was also detected after exposure to that petroleum derivative. Besides, morphological analysis through scanning electron microscopy revealed irregularities in the cell surface, as transmission electronic microscopy indicated an increased number of vacuoles in the cells. Based on these results, it could be concluded that the acute exposure to diesel oil brings about a stress effect in S. cymosum var. stenophyllum, promoting alterations in the seaweed secondary metabolism, stimulating protective mechanisms against oxidative stress, and changing cell's morphological and ultrastructural traits.