Resumo

ZAMORANO, Carolina  e  FUENTES, Cilia L.. Alelopatic potential of Brassica campestris subsp. rapa and Lolium temulentum on tree weed species on the Sabana de Bogotá. Agron. colomb. [online]. 2005, vol.23, n.2, pp.261-268. ISSN 0120-9965.

Laboratory and glasshouse assays were carried out to evaluate the alelopatic potential of turnip (Brassica campestris subsp.rapa [L.] Hook. f.) and ryegrass (Lolium temulentum L.) aqueous leaf extracts and foliar tissue residues on three common weed species from the Bogotá plateau: Chenopodium petiolare Kunth, Fuertesimalva limensis (L.) Fryxell, Amaranthus hydridus. The seedling technique was used with nutrient solution in laboratory completely random bioassays (repeated 3 times with 3 replications). Plastic plant-pots were employed in greenhouse assays using sand:peat (3:2) as substrate and pre-germinated seeds. Results obtained in the laboratory showed differences regarding the symptoms observed amongst the different species, whilst fresh weight was the one that best described the effect of turnip extracts having DC₅₀: 5.53 g· L^-1 for Amaranthus hydridus, 2.58 g· L^-1 for Chenopodium petiolare and 7.72 g· L^-1 for Fuertesimalva limensis. The fresh weight of ryegrass allowed a concentration-response curve to be adjusted for calculating DC₅₀. Greenhouse results revealed a different response for extracts and residues; there were no differences between turnip residues and extracts in Amaranthus hydridus seedling weight; Chenopodium petiolare and Fuertesimalva limensis seedlings did not emerge. The fresh weight of tomato seedlings, grown in turnip waste became reduced by around 25% (6 or 12 t· ha^-1 fresh weight) and by about 60% when grown in ryegrass waste (6 t· ha^-1 fresh weight).

Palavras-chave : allelopathy; Chenopodium petiolare; Fuertesimalva limensis; Amaranthus hybridus; plant extracts; plant residues.

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