Two experiments, a Petri dish assay and a pot experiment were carried out to evaluate possible allelopathic effects of water extracts (0, 10 and 20 gL-1) of sugar beet (Beta vulgaris) and eucalyptus (Eucalyptus camaldulensis) on germination and growth of purslane (Portulaca oleracea). Results showed that germination percentage of purslane seeds was not inhibited by concentration of water extract of tested plants. However, seed vigour index and seedling growth strongly influenced by aqueous extracts of tested plants. Maximum inhibitions on seedling growth were recorded when using the higher concentration of the aqueous extract (20 gL-1). It was apparent that sugar beet had a greater inhibitory effect than eucalyptus. Shoot length of purslane seedlings significantly decreased at 10 and 20 gL-1 aqueous extract concentration of sugar beet by 65.5 and 92.1%, respectively compared to the control, while eucalyptus decreased seedling shoot length of target weed at 10 and 20 gL-1 extract concentration by 29.8% and 52.9%. Root length was more affected than shoot so that low aqueous extract concentration (10 gL-1) of sugar beet and eucalyptus decreased root length of target weed by 79.8% and 46%, respectively. Foliar sprays with both 10 and 20 gL-1 of tested plants extracts significantly decreased leaf area, leaves, stem and root dry weight of purslane weed. Maximum leaf area (1010 cm2) was obtained from the untreated plants (0% extract), while the lowest value (166.6 cm2) occurred with 20 gL-1 water extract of sugar beet. High aqueous extract concentration (20 gL-1) of sugar beet decreased leaves, stem and root dry weight of purslane plants by 96%, 86.7% and 91.9%, respectively compared to controls.

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