Allelopathic Effects of Harmal (Peganum harmala L.) Aqueous Extract on Seed Germination and Seedling Growth of Purslan (Portulaca oleracea L.) and Black Weed (Chenopodium album L.)

Background: The study of allelopathic properties of plants is one of up-to-date biological and ecological methods, which can lead to discover the bio-herbicides and growth inhibitors. Objective: In order to study the allelopathic effects of harmal (Peganum harmala L) on seed germination and seedling growth on purslan (Portulaca oleracea L.) and black weed (Chenopodium album L.), these experiments were conducted. Methods: The aqueous extracts of harmal different organs including capsule, leaf, stem and root were applied at five concentration levels (0 as control, 1, 5, 10 and 15%) through a factorial experiment based on a completely randomized design with three replications. Results: The results showed that different organ extracts had different negative effects on seed germination and seedling growth of the two species in such a way that capsules extracts had the highest inhibitory effect. With increasing extract concentrations of harmal, the seed germination and seedling growth of the two species was reduced significantly. The minimum amount of seed germination and growth of the seedlings were observed at 15% extracts concentration of capsules. Also, purslan seedlings appeared to be more sensitive to harmal extracts than black weed seedlings. Conclusion: The aqueous extracts of harmal different organs had inhibitory effects on seed germination and seedlings growth of purslan and black weed. Also, the highest inhibitory effects were related to capsule extracts