Allelopathic effect of sugar beet (Beta vulgaris) and eucalyptus (Eucalyptus camaldulensis) on seed germination and growth of Portulaca oleracea

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 g L^?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 test plants. However, seed vigour and seedling growth strongly influenced by aqueous extracts of test plants. Maximum inhibitions on seedling growth were recorded when using the highest concentration of the aqueous extract (20 g L^?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 g L^?1 aqueous extract concentration of sugar beet by 65.5 and 92.1% respectively compare to control, while eucalyptus decreased seedling shoot length of target weed at 10 and 20 g L^?1 extract concentration by 29.8% and 52.9% respectively. Root length was more affected than shoot so that low aqueous extract concentration (10 g L^?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 g L^?1 of test plants extracts significantly decrease leaf area, leaves, stem and root dry weight of Portulaca oleracea. Maximum leaf area (1010 cm²) was obtained from the untreated plants (0% extract), while the lowest value (166.6 cm²) occurred with 20 g L^?1 water extract of sugar beet. High aqueous extract concentration (20 g L^?1) of sugar beet decreased leaves, stem and root dry weight of purslane plants by 96%, 86.7% and 91.9% respectively.