Review Article
Shima Alipour1, Ezatollah Fars
Abstract
The allelochemicals or secondary plant metabolites when are released to environment, influence the germination and seedling growth of neighbors' weeds. The aim of this study was to investigate the effect of the extract of St Johnson wort (Hypericum perforatum) on the number and mass of weed seedlings and their seed germination under laboratory conditions. The St Johnson wort extracts were considered with different concentrations (1.25 to 20%) on the germination and seedlings growth of Zea maize, Johnsongrass (Sorghum halepense), Common lambsquarter (Chenopodium album) and Redroot pigweed (Amaranthus retroflexus) for 5 days. Results showed that with increasing concentration of St Johnson wort extracts, their effects on reducing seed germination and seedling growth of the above mentioned plants were more severe. Comparison of extract effects with polyethylene glycol, revealed that reduction of Johnsongrass, corn seed germination and length of plumules were attributed to the osmotic pressure of the extract, where, inhibition of seed germination of Redroot pigweed and Common lambsquarter was due to allelochemicals.