[Inhibitory effects of dry Acorus calamus extracts on the growth of two water bloom-forming algal species].

A trial with different concentrations of aqueous extracts from dry Acorus calamus plants was conducted to study the effects of the extracts on Microcystis aeruginosa and Chlorella pyrenoidosa growth. Allelopathic effects were observed. High concentration ( >40 ml x L(-1)) extracts inhibited the growth of the two algal species at low inoculation cell density significantly (P < 0.01), with the maximal inhibition rate being 98.66% for M. aeruginosa and 92.38% for C. pyrenoidosa, while low concentration ( < 30 ml x L(-1)) extracts promoted the growth of C. pyrenoidosa. Neither high nor low concentration extracts had significant effects on the growth of the two algal species at high inoculation cell density (P > 0.05). The comparison of adding the aqueous extracts once and semiconsecutively showed that the allelochemicals in the extracts were easy to be degraded, suggesting that the continuous secretion of allelochemicals in natural water bodies could play an important role in inhibiting algal growth.