Although
P. crispus was previously found to have no allelopathic
activity
on different groups of microalgae (Nakai et al., 1999), our
study
revealed a strong allelopathic effect on A. variabilis, particularly
in Exp. I and II. The inhibitory effect of P. crispus shoots on
A.
variabilis persisted in Exp. II even after the macrophytes died
and
the material started to decompose. The decaying material of
some
species is capable of producing allelochemicals (Ridge and
Pillinger,
1996; Hu and Hong, 2008; Zeng et al., 2008), hence it could
be
inferred that the residue of this macrophyte was also producing
allelochemicals.