Effect of isomers of hydroxybenzoic acid on the growth and metabolism of Chlorella vulgaris Beijerinck (Chlorophyceae)

The isomers <em>o-</em>, <em>m-</em>, and <em>p-</em> of hydroxybenzoic acid (HBA) in the concentration range 10^-1-10^-4 M in the unicellular green alga <em>Chlorella vulgaris</em> (<em>Chlorophyceae</em>) display marked biological activity. The <em>o-</em>HBA isomer, commonly known as salicylic acid, in a concentration of 10^-4 M exerted the most stimulating effect on the parameters analysed (the number of cells, dry mass, the content of chlorophylls a and h, carotenoids, soluble proteins and their secretion, monosaccharides, DNA and RNA) whereas p-HBA had weak stimulating properties. On the other hand, m-HBA had a weak inhibitory effect on the growth of <em>C. vulgaris</em> and all the biochemical parameters analysed in comparison with the control culture of algae devoid of HBA isomers.