Allelopathic effects of foliage extracts from four Chenopodiaceae species on seed germination

The effects of allelochemicals may play an important role, indirectly, in determining chenopod community structure in the and and semi-arid zones of Western Australia. The aqueous and methanol extracts of the leaves of four chenopod species were assayed at 0.006, 0.06, 0.63, 1.55, 3.12, 6.25 gl(-1) and 0.025, 0.25, 2.5, 6.25, 12.5, 25 gl(-1) respectively, for allelopathy. The extracts were tested with the widely used lettuce seed test and on the seeds of the chenopod species themselves. Seed germination was inhibited at concentrations ranging from 3.12 and 6.26 gl(-1) in the lettuce seed tests indicating the presence of allelopathic substances. The inhibition of root and shoot growth was also observed in the lettuce seed. The seed of the chenopods, Enchylaena tomentosa R. Br. and Maireana georgei (Diels) Paul G. Wilson, were also inhibited by extracts of the leaves of Atriplex bunburyana F. Muell. and Atriplex codonocarpa Paul G. Wilson. A. codonocarpa was not, in contrast, affected by extracts derived from the leaves of E tomentosa and M. georgei. All four species were susceptible to allelopathy by extracts isolated from leaves of their own respective species. Interestingly, seed germination in E. tomentosa was promoted by a 0.006 gl(-1) aqueous extract of its own leaves. The results from this study strongly suggest that allelopathy may be a possible mechanism controlling the timing of chenopod germination and seedling establishment. (C) 2003 Elsevier Science Ltd. All rights reserved.