The Effect of Gibberellic Acid (GA_3) on Growth, Metal Biosorption and Metabolism of the Green Algae Chlorella vulgaris (Chlorophyceae) Beijerinck Exposed to Cadmium and Lead Stress

摘要

The aim of this work was to show how gibberellic acid (GA_3) affects growth, metal biosorption, and the content of essential metabolites (cell number, proteins, monosaccharides, chlorophyll a and b, and total carotenoids) in unicellular green algae Chlorella vulgaris treated with lead (Pb) and cadmium (Cd) during 3 days of culture. Under the influence of 10~(-5) M GA_3, algal cells bioaccumulated and bioconcentrated toxic metals from nutrient medium in a dose- and exposure-dependent manner. Moreover, this phytohormone protected C. vulgaris against Pb and Cd stress at a range of low concentrations 10~(-7)-10~(-6) M inducing the increase in cell number and protein, photosynthetic pigment, and monosaccharide content in the culture. However, GA_3 was not able to minimize the harmful effects of the highest dose (10~(-4) M) of Cd and Pb, because growth inhibition and reduction in metabolite level was observed. The data suggest that GA_3 plays an important role in the growth and metabolism of microalgae C. vulgaris exposed to heavy metal stress and its adaptation ability to a low-level polluted aquatic environment.