The Study of Biogeochemical Variations of Heavy Metals in the Rhizosphere of Hyper-Accumulator Barley Crop.

Soil as a major component of the environment, receives various types of waste, and its quality can affect the health and survival of organisms. Heavy metals are those soil contaminants that have a long lasting and Remaining in the soil, so through uptake by plants enter to the food chains and caused toxic to human and animals. Thus, recognizing their effects on plant growth and finding ways to mitigate the injury are the essential points in the cultivation of plants in heavy metals contaminated soils. To study the effects of heavy metals contaminated soils on barley yield and yield components and also using PGPR to mitigate the negative effects, a factorial experiment in a randomized complete block design with three replications was conducted. Three factores were, salinity (irrigation with saline water and non-saline), plant growth promoting rhizobacteria (non-inoculated control and hnoculation with PGPR) and soil quality ( low and high polluted soils) which were applied in pots so called rhizobox. 6 barley seeds were planted per rhizobox. After harvest, shoot and root dry weight, heavy metals such as lead, zinc and cadmium were measured in both soil and plants. Statistical analysis of the data showed that soil contamination had significant effect on dry weight and the amount of heavy metal in plants, so the root and shoot dry weight were significantly greater in soils with low pollution, but the amount of lead, zinc and cadmium were lower in plants which grown in soils with low pollution. Salinity also reduced the growth and dry weight of shoot and root, as well intensified the concentration and content of heavy metals in plants and increased the concentrations and content of heavy metal in both soils, this effect was greater in soils with high pollution. Plant inoculation with PGPRs han no significant effect on indices measured in the shoot but increased roots lead content and soil lead concentration. Key words: Barley, Heavy metals, Phytoremediation, Plant Growth Promoting Rhizobacteria (PGPR), Pb, Cd, Zn