Allelopathic effect of marigold (Tagetes erecta L.) leaf extract on growth of Chlorella vulgaris

Marigold (Tagetes erecta L.) is a perennial edible medicinal plant. In order to test the allelopathic effect of marigold leaf extract on Chlorella vulgaris, the microalgae growth conditions under different concentrations of marigold leaf extract (0 to 50 g/l) were studied. The results showed that microalgal growth was inhibited by marigold leaf extract, and inhibition commonly increased with increasing concentration of the extract and culture time. The maximum inhibition rate (90.1%) appeared in leaf extract of 30 g/l after 14 days of incubation; marigold leaf extract induced chlorophyll degradation in algae cells, increased the permeability of cell membrane, and caused exudation of soluble protein and nucleic acid, leading to the damage of algae cell structure and metabolic dysfunction. The present results confirmed that marigold leaf extract has an allelopathic inhibition effect on C. vulgaris, and the results could be further applied to develop safe and efficient algaecides.