Effects of drought on allelopathic activity of Datura stramonium L.

Abstract

The effects of drought on young plants of thorn-apple were evaluated by (a) the area and water content of leaves, dry weight of leaves, stems, shoots and roots, (b) stomatal frequency of upper and lower leaf epidermis, (c) allelopathic activity of water extracts of leaves and roots on germination and root growth of cucumber. No differences were found between irrigated and droughted plants in leaf water content, leaf area, dry weight and derived parameters of growth analysis. Stomatal frequency was increased by drought in both upper and lower epidermis. Leaf extracts stimulated root length of cucumber, having no effect in the number of lateral roots. Root extracts reduced root length and number of lateral roots. Differences in allelopathic activity of irrigated and droughted plants were found only in root extracts. Therefore, even if thorn-apple growth is not affected, the drought treatment alters secondary metabolites activity and stomatal frequency. Differences of allelopathic activity between leaf and root extracts and within root extracts are discussed in terms of sites of production of alkaloids, their activity and relative investment on plant building vs. production of secondary metabolites.