| dc.description.abstract | The objective of this thesis was to determine the interference
potential of aquatic plants to wild rice (Zizania palustris L. )
through field and laboratory studies. Three companion papers
describe the influence of aquatic plants on growth of wild rice;
the allelopathic potential of aquatic plants and the isolation and
identification of allelochemicals from two selected plants.
The growth of wild rice in the presence cind in the absence of
different plemt species, namely Eleocbaris smallii, Scirpus acutus,
Equisetum fluviatile, Nymphaea odorata, Nupheur variegatum,
Sparganium fluctuans, ttyriophyllum verticillatum and Potamogeton
natans was studied. Number of wild rice plants and their growth
decreased in the presence of different plant species. Environmental
factors had no influence on the growth of wild rice, either in the
presence or absence of different species. It is suggested that the
adverse effects of different species on wild rice may be due to
either their early growth habit, shading the wild rice plant, or to
their allelopathic effects.
The allelopathic potential of the above mentioned plant
species was examined using lettuce and wild rice seedling
bioassays. The root length of lettuce and the total root length of
wild rice seedlings were significantly reduced by aqueous extracts
of these plant species. The lettuce seedling bioassay was more
responsive than that of wild rice. Shoot growth was less affected.
Bioassay with an aqueous extract of lake sediments associated with
these species had little inhibitory effect on growth of wild rice
seedling. The use of teurget species as a bioassay material and
further studies on phytotoxic effect of lake sediments have been
emphasized for evaluating their ecological significemce.
The phytotoxic compounds from water extracts of the rhizome
of Scirpus acutus and the shoot of Eleocbaris smallii were isolated
by ethyl acetate extraction emd identified by GC-Mass spectroscopy.
The ethyl acetate organic fraction of water extract of Scirpus
rhizomes contained lactic, succinic, fumaric, 2-hydroxy succinic,
2-phenyl lactic, m-hydroxy benzoic, p-hydroxy benzoic,
protocatechuic, dehydroêüaietic and ferulic acids; p-hydroxy benzyl
alcohol, p-hydroxy phenyl ethanol and a dye, catechin. The organic
fraction of the extract of Eleocbaris shoots contained 4-methoxy
phenol, benzofuran, benzene acetic acid, l-hydroxy-5-methyl
acetophenone and 1,3,4-dimethoxy phenyl ethanone. The growth
inhibiting properties of some of these compounds under field
conditions are discussed. | |
