| dc.description | The term allelopathy was first defined as the influence of one plant to another
plant by releasing chemicals (Molish, 1937). The chemicals release from one
plant and which has direct or indirect beneficial or harmful effect on other
plant is called allelochemicals (Rice, 1984b). A substantial number of
allelochemicals have been identified but most of these are secondary plant
metabolites which belonging to the groups of terpenoids, phenolic compounds,
long chain fatty acids, organic cyanides, organic acids, alkaloids and others
(Macias, et al., 2001; Oleszek and Stochmal, 2002). Organic acids are major
water soluble allochemicals that can be inhibited seedlings growth, by altering
nutrient uptake and transport, by reducing chlorophyll content.
(Baziramakenga, et al., 1994). These organic acids, especially phenolic acids,
such as cinnamic, vanillic, coumaric, and benzoic acid have been isolated and
identified as allelochemicals (Ohno, et a/., 2001; Yu, et al., 2003; Asao, et al.,
2003; Hao, et al., 2006; Lee, et al., 2006; Wu, eft al., 2008a,b). 4-hydroxy
benzoic acid one of the secondary plant metabolites inside the plant which is
potential phytotoxic allelochemicals (Bolwell, et al., 1986; Wu, et al/., 2001;
Yu, et al., 2003). This compound has also been identified and isolated in
Leonurus siribicus L. (Sheng Ming, et al., 2006). They also isolated various
phenolic compounds like 4-hydroxythiophenol, syringic acid, apigenin,
genkwanin, isoquercitrin and rutin. In another studied showed that syringic
acid and 4-hydroxybenzoic acid are closely related to allelopathic effect on
some plants (Sasikumar, ef a/., 2001). Leonurus sibiricus L. (Lamiaceae), plant
native of India and now naturalized in South America, contains terpenoids and
phenolic substances with demonstrated allelopathic effects (Larcher, 2000). | en_US |
| dc.description.abstract | The aim of this work was to investigate the allelopathic effect of honeyweed
extract on seed germination and seedlings growth of wheat. Varying doses (5,
10 and 15%) of the aqueous extract of the honeyweed leaves were applied to
surface sterilized wheat seeds at starting and 5 days after placing for
germination on water soaked filter papers in the petri dish. The extracts of
honeyweed inhibited seed germination and growth of wheat seedlings in dose
and time dependent manage. Interestingly 5% aqueous extract displayed
stimulatory effects on growth of the seedlings, however application of 10 and
15% extracts inhibited the growth seedlings, when applied at 5 days after the
mechanism of inhibitory effects on seeds of honeyweed extracts on wheat. The
dry matter of wheat seedlings were decreased with increasing the extract
concentration. Thin layer chromatography of the methanol extract of
honeyweed suggested the presence of 4-hydroxy benzoic acid including other
allelopathic compounds in honeyweed inhibited germination and seedlings
growth. Mineral composition was determined, they might have some
stimulatory effect on seedlings growth. It was interesting that 5% extract
inhibited germination and seedlings growth, when it was applied during the
time of seed germination, but stimulated seedling growth, when it was applied
at 5 days after germination. To find out molecular mechanism behind it,
further research is to be done. | en_US |
