Effect of cadmium and aluminum on growth, metabolite content and biological activity in Drimia elata (Jacq.) Hyacinthaceae
2015
Drimia elata (Jacq.) is a bulbous plant that is extensively utilized in South African traditional medicine. This study investigated the effects of cadmium (Cd) and aluminum (Al) on growth, heavy metal bioaccumulation, metabolite content and antibacterial activity in D. elata. Seeds were germinated and after seven months, plants were exposed to various concentrations of Cd and Al both singly and in combinations for six weeks. Thereafter, the experiment was terminated and the mean fresh (FW) and dry weights (DW) of the bulb and shoot biomass recorded. Dried samples (0.5gDW) were analyzed for Cd and Al accumulation using Inductively Coupled Plasma-Optical Emission Spectroscopy. In addition, total chlorophyll, free-proline, total phenolic and flavonoid content were quantified as a measure of plant stress. Antibacterial activity was assessed using the microdilution assay and the activity was correlated to heavy metal and secondary metabolite content. Plants exposed to heavy metals generally exhibited a marked reduction in plant biomass. The highest Cd content (83mg/kg) was recorded in bulbs grown in Cd 5:Al 1000mg/l. There was a significant increase in free-proline and a significant reduction in the chlorophyll, phenolic and flavonoid content in plants exposed to increasing concentrations of Cd and Al. This decrease in secondary metabolite content may account for the poor antibacterial activity of plants grown in most of the heavy metal treatments. This results indicate that exposure of D. elata to heavy metal contaminated soil may potentially compromise the health of the consumer due to heavy metal bioaccumulation as well as reduced efficacy of the herbal product.
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