Allelopathic effects of Eucalyptus citriodora on amaryllis and associated grassy weed

Abstract

-A Petri dish assay was carried out for screening different concentrations of aqueous extracts of fresh and dry leaves of Eucalyptus citriodora on germination and seedling growth of wild oat weed (Avena fatua). Seed germination, root and shoot length of wild oat exhibited different degrees of inhibition according to the concentration of the aqueous extract. Maximum inhibitions of germination percentage, root and shoot length were recorded when using 25% fresh leaf extract. Based on this preliminary work (Petri dish assay), studies were conducted under greenhouse conditions at the National Research Center, Egypt, in the two winter seasons of 2006/2007 and 2007/2008 to evaluate the effects of foliar and soil treatments of aqueous extracts of Eucalyptus citriodora fresh and dry leaves on wild oat weed as well as on the growth and flowering of amaryllis (Hippeastrum hybridum), compared with the recommended dose of the herbicide tralkoxydim. Amaryllis fresh and dry weights as well as flowering increased significantly when treated with the previous extracts, especially the fresh leaf extract. However, the fresh and dry weights of wild oat were significantly reduced by the aqueous extracts, either fresh or dry, indicating phytotoxic effects. Tralkoxydim caused complete inhibition of wild oat as compared with the control. The studies involved estimation of the endogenous contents of total phenols in weed. With all the treatments, the inhibitory effects on weeds were correlated with accumulation of the internal contents of total phenols, compared to their respective controls. The amount of phenols correlated well with the weed's growth performance. This study establishes the effect of the aqueous extracts on the weed wild oat, associated with amaryllis, which may serve as a tool in establishing their herbicidal potential.Keywords: aqueous extract, herbicide, phytotoxic, total phenols, tralkoxydim.RESUMO -Um experimento em placas de Petri foi realizado para a seleção de diferentes concentrações de extratos aquosos de folhas frescas e secas de Eucalyptus citriodora na germinação e no crescimento inicial de aveia-selvagem (Avena fatua). A germinação da semente, a raiz e o comprimento da brotação apresentaram diferentes graus de inibição, de acordo com a concentração do extrato aquoso. As maiores porcentagens de inibição da germinação, de raiz e de comprimento de brotação foram registradas com extrato fresco das folhas a 25%. Com base no trabalho preliminar (experimento em placa de Petri), foram conduzidos estudos na estufa do Centro de Pesquisa Nacional, Egito, em duas estações de inverno: 2006/2007 e 2007/2008. Nesse local, foram avaliados os efeitos de tratamentos foliar e do solo de extratos aquosos das folhas frescas e secas de Eucalyptus citriodora na aveia-selvagem, assim como no crescimento e no florescimento da espécie Hippeastrum hybridum, em comparação com a dose recomendada do herbicida tralkoxydim. Os pesos frescos e secos do amarílis sofreram aumento significativo, bem como o florescimento, quando tra...

Biological, medicinal and toxicological significance of Eucalyptus leaf essential oil: a review

“…Different concentrations of aqueous extracts of fresh leaves of E. citriodora had an inhibitory effect on germination and seedling growth of wild oat weed ( Avena fatua ). Fresh and dry weight of wild oat was significantly reduced, indicating phytotoxic effects . Some results suggest that Eucalyptus should be further explored as a bioherbicide for weed management.…”

“…Fresh and dry weight of wild oat was significantly reduced, indicating phytotoxic effects. 201 Some results suggest that Eucalyptus should be further explored as a bioherbicide for weed management. This control option could be an alternative to arrest the rapid evolution of herbicide resistance in annual ryegrass and barley grass.…”

Shade Effects on Leaf Production and Essential Oil Content and Composition of the Novel HerbEucalyptus citriodoraHook.

“…E. citriodora is grown extensively worldwide, mainly for the paper and wood industries, and to a lesser degree for its leaf essential oils. The essential oils are produced commercially mainly in China, India and Brazil 1 , and are mostly used for perfumes or medicines as pain reliever 2,3 , antifungal 4,5 , allelopathic [6][7][8][9][10][11] , insect repellent agent [12][13][14][15][16] and recently as biomass feedstock for production of biofuels 17,18 . The leaf-essential oils of E. citriodora includes nearly 100 volatile compounds 1,19 , all contributing to the final lemony, rose-like odor.…”

Phytotoxic potential of sugar beet (Beta vulgaris) and eucalyptus (Eucalyptus camaldulensis) to control purslane (Portulaca oleracea) weed

“…Phenolic acids have been shown to be toxic to germination and plant growth processes (Enhilelling, 1995). El-Rokiek and Eid (2009) reported that the inhibitory effects of eucalyptus on weeds correlated with accumulation internal contents of total phenols, compared to their respective controls. Accumulation of phenols is often characteristic of stress conditions (El-Rokiek, 2002, 2007.…”

“…Dadkhah (2012a) reported that growth traits of Cirsium arvense weed significantly decreased when sprayed with aqueous extract of Ephedra major. Allelopthy associated with plants due to the presence of allelochemicals such as monoterpences, phenolic and volatile compounds in their foliage (El-Rokiek & Eid, 2009). Therefore, this study aimed to evaluate the effect of foliar aqueous extract of Eucalyptus camaldulensis and Beta vulgaris on germination, seedling growth and plant growth parameters of a widespread weed species P. oleracea which cause major constraints to crop production in Iran.…”