Abstract
Secondary metabolites in medicinal plants could lead to discovery of new classes of herbicides. Recently aromatic plants have gained interest as a source of allelopathic secondary metabolites. Origanum vulgare ssp. vulgare L. infusions in hot water are used in folk medicine and possess proved beneficial biological activity. Plant-to-plant variability of metabolites due to genetic heterogeneity is established in Lamiaceae family. From this point of view, studies on plants from different geographic regions might reveal important sources of variability. The objective of this study was to evaluate allelopathic activity of cold water extracts made from the aerial parts of O. vulgare ssp. vulgare growing wild in Northeast Bulgaria in laboratory conditions. The allelopathic effect was evaluated using root elongation test and Allium cepa-test. Oregano extracts (17.5 g/l, 52.5 g/l) significantly decreased root length of Triticum aestivum L. (P ≤ 0.001). The root growth reduction could serve as a sign for presence of water soluble allelopathic secondary metabolites in the plant tested. Oregano (3.5 g/l) inhibited cell division in Allium root meristematic cells. The decline of the mitotic index indicates the occurrence of a cytotoxic effect. Oregano induced abnormalities in mitotic and interphase cells, so can be also considered as genotoxic. The observed macroscopic and microscopic effects of tested extracts indicated presence of water soluble allelochemicals in O. vulgare ssp. vulgare. This characteristic could be further studied as a possibility to be used in weed management programs.
Highlights
Oregano (Lamiaceae) is a valuable aromatic plant found in natural conditions in Europe, Central Asia and North America [1]
In present study root growth inhibition of T. aestivum was used as index of general toxicity [27] [28]
The established root growth reduction could serve as a sign for presence of water soluble allelopathic secondary metabolites in the plant tested
Summary
Oregano (Lamiaceae) is a valuable aromatic plant found in natural conditions in Europe, Central Asia and North America [1]. The renewed interest in allelopathy to a great extent is due to the necessity to reduce synthetic chemical input into agriculture [3] [4]. According to [5] aromatic plants, such as oregano, could be used in agriculture for the suppression of some weeds. Allelochemicals could cause inhibition of seed germination and/or seedling growth [6]. According to [10] the inhibition of root growth and development by allelochemicals can be due to changes in DNA synthesis in cells of apical root meristem, alteration of the mitochondrial metabolism [11] or changes in cell mitotic indices [12]-[15]
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