The term allelopathy, literally meaning
mutual harm, refers to the positive or negative
influences of one plant with or without microbial
action upon anotherthroughchemicalmeans other
than nutritional. Allelopathy depends on
chemical compounds mainly added to the environment from living plants or dead and decaying
parts(Tang 1986). Thenumber and diversityofthe
compounds involved in allelopathy are growing
rapidly. These chemicals may be produced by
various parts of the plant such as roots and leaves
(Horseley 1977), pollen (Ortega et al. 1988), seeds
or fruits (Friedman et al. 1982), although roots and
leaves are the main sources (Horseley 1977).
Autotoxicity is apparently a negative feature of
allelochemical production avoided by some
species through excreting or sequestering of
chemicals involved in structures. The
allelochemicals can be classified based on the
nature of producers, systematics of donor and
receiver, inhibitory and stimulatory activity or
upon the self or alien origin. During the last few
years effortshave beenmade to exploitallelopathy
for weed management, pest management,
comparison and rational cropping, agroforestry
and other