Abstract

CAZON, Ada; DE VIANA, Marta L  and  GIANELLO, José C. Comparative phytotoxic effects of Baccharis boliviensis (Asteraceae) allelochemicals on the germination of Trichocereus pasacana (Cactaceae). Ecol. austral [online]. 2002, vol.12, n.1, pp.73-78. ISSN 1667-782X.

The genus Baccharis has a wide distribution in the arid regions of Northwestern Argentina. One species of this genus, Baccharis boliviensis, growths in association with other plant species at Los Cardones National Park, Salta Province. Studies carried out on the spatial distribution of the cacti Trichocereus pasacana in relation to available space show that although cacti seeds are abundant beneath Baccharis boliviensis canopy, no adult plants are found growing in association with this species, in spite of the requirement of a nurse plant for a successful cacti establishment. Aqueous extracts from Baccharis boliviensis foliage extracted with hexane, chloroform and ethyl acetate inhibited Trichocereus pasacana germination. Chloroform was the most effective solvent for extracting the phytotoxic compounds. From this extract we isolated three flavonoids whose structures were determined by spectroscopic methods and TLC in silica gel. The germination bioassay showed that Trichocereus pasacana had a differential response to the compounds from the tested extracts. The inhibitory effect was only detected in the chloroformic extract, which suggests a synergistic effect.

Keywords : Allelopaty; Baccharis boliviensis; Trichocereus pasacana; Chromatography; Inhibition; Facilitation.

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