The results of vegetation experiments carried out over 12 of years in order to assess the application of Sorghum bicolor (L.) Moench) for soil clean up from oil hydrocarbons and heavy metals in the Saratov Region are given. It was found that the cultivation of sorghum in contaminated soils under controlled conditions for 2 to 4 months led to the elimination of hydrocarbon pollutants by 21-98%. The decrease in the concentration of oil and oil sludge occurred primarily due to the reduction of the content of paraffins and naphthenes fractions. The degradation of diesel fuel and of phenanthrene as an individual polycyclic aromatic hydrocarbon was most successful. The role of the plant in the manifestation of the rhizosphere effect and of the pollutant detoxification was suggested to be based on the coupled plant-microbial metabolism of pollutants in the rhizosphere. The high extracting activity of sorghum towards heavy metals such as cadmium and nickel was revealed. Sorghum plant can accumulate up to 1003 mg of metals per kg of dry biomass. It was shown that cadmium predominantly accumulated in the sorghum roots. High concentrations of nickel accumulated in the plant shoots. Special attention is paid to phytoremediation of mixed pollution of soil with hydrocarbons and metals. A significant mutual influence of petroleum hydrocarbons and heavy metals on their elimination from soil has been established. The presence of organic pollutants reduces cadmium and nickel extraction capacity of sorghum. In contrast, cadmium increased the degradation of oil sludge. The data obtained emphasize the need for more detailed studies of the mutual influence of the components of mixed pollution in order to understand and predict the cleaning up processes in the environment. In general, taking into account the economic and biological characteristics of sorghum crops, it was concluded that the application of sorghum is promising for phytoremediation of contaminated soil in the Saratov Region.
The physiological and biochemical activity of plant–microbial associations enables them to determine the mobility, bioavailability, and accumulation of heavy metals in plant tissues. These abilities are the basis for the use of plants and their associated microorganisms in the development of approaches that ensure both the prevention of the ingress of toxic metals into food crops and the extraction of pollutants from polluted soils by using phytoremediation technologies. Whether plant–microbial complexes are used successfully depends on the knowledge of how specific organisms interact with heavy metals. We evaluated the effect of copper ions on common wheat (Triticum aestivum L.) inoculated with three plant-growth-promoting rhizobacteria (PGPR) of the genus Azospirillum. We analyzed the growth variables of 14-day-old wheat seedlings, the content of photosynthesis pigments, the activity of plant oxidoreductases, and the accumulation of copper by plant tissues. All strains more or less compensated for copper toxicity to seedling development and increased metal accumulation in roots and shoots. Copper affected the photosynthetic apparatus of the inoculated plants, primarily by decreasing the content of chlorophyll b. An analysis of the activity of plant oxidoreductases (peroxidases and phenoloxidases), which are involved in the physiological responses of plants to pollutant stress, showed strain-specific dependence and a significant effect of copper on the inoculated plants. Overall, the obtained results clearly show that the effect of Azospirillum on the physiological and biochemical status of wheat is diverse. The compensatory effect of bacteria on copper toxicity and the simultaneous increase in metal accumulation in plant tissues can be considered as mutually exclusive crop-production aspects associated with the growing of food plants in heavy-metal-polluted areas.
An extracellular polysaccharide (EPS) produced by the gramnegative nonpathogenic rhizosphere bacteria Enterobacter cloacae K7 was isolated and characterized. The process of biosorption of Cu(II) cations from aqueous solution by the isolated exopolysaccharides was investigated. The maximum sorption capacity was 0.17 mM/mg of EPS or 12 g of Cu(II) per g of EPS at pH 5, T = 25 °C, and incubation for 30 min. The experimental values of the
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.