Role of plant growth promoting rhizobacteria in the remediation of metal contaminated soils

Abstract

Pollution of the biosphere by the toxic metals is a global threat that has accelerated dramatically since the beginning of industrial revolution. The primary source of this pollution includes the industrial operations such as mining, smelting, metal forging, combustion of fossil fuels and sewage sludge application in agronomic practices. The metals released from these sources accumulate in soil and in turn, adversely affect the microbial population density and physico-chemical properties of soils, leading to the loss of soil fertility and yield of crops. The heavy metals in general cannot be biologically degraded to more or less toxic products and hence, persist in the environment. Conventional methods used for metal detoxification produce large quantities of toxic products and are costeffective. The advent of bioremediation technology has provided an alternative to conventional methods for remediating the metal-poisoned soils. In metal-contaminated soils, the natural role of metal-tolerant plant growth promoting rhizobacteria in maintaining soil fertility is more important than in conventional agriculture, where greater use of agrochemicals minimize their significance. Besides their role in metal detoxification/removal, rhizobacteria also promote the growth of plants by other mechanisms such as production of growth promoting substances and siderophores. Phytoremediation is another emerging lowcost in situ technology employed to remove pollutants from the contaminated soils. The efficiency of phytoremediation can be enhanced by the judicious and careful application of appropriate heavy-metal tolerant, plant growth promoting rhizobacteria including symbiotic nitrogen-fixing organisms. This review presents the results of studies on the recent developments in the utilization of plant growth promoting rhizobacteria for direct application in soils contaminated with heavy metals under a wide range of agro-ecological conditions with a view to restore contaminated soils and consequently, promote crop productivity in metal-polluted soils across the globe and their significance in phytoremediation.

Could Uptake and Acropetal Translocation of PBDEs by Corn Be Enhanced Following Cu Exposure? Evidence from a Root Damage Experiment

“…31 In addition, excess Cu can induce a number of free radical processes in proteins and lipid cell membrane components, 32,33 resulting in destabilization of membranes and an increase in their permeability. 34 In the present study, electrolytic leakage was used to monitor the permeability of root cell membranes after exposure to Cu.…”

Salt Stress Effects on Avocado (Persea americana Mill.) Plants with and without Seaweed Extract (Ascophyllum nodosum) Application

“…Seaweed extracts have been determined to be a complex mixture of organic and mineral components and plant hormones [26]. Numerous reports show the beneficial effects of seaweed extracts on shoot growth and crop yield, and seaweed extracts have been shown to alleviate a variety of abiotic stresses, including drought and salinity [7].…”

Remediation of heavy metal contaminated ecosystem: an overview on technology advancement

“…With improvement the growth and yield of the Cicer arietinum, Vigna radiata and Pisum sativum, metal toxicity is also decreased with the help of PGPR (Gupta et al 2004;Wani et al 2007Wani et al , 2008. With the help of PGPR the increase in the growth and reduction in the metal toxicity is due to enhancement in soil nutrient so it is one of the most suitable choices for bioremediation (Zaidi et al 2003;Khan et al 2009). Heshmatpure and Rad (2012) have also observed that the Pseudomonas fluorescence plant growth-promoting rhizobacterium increases the resistance against high levels of Cd and reduces its adverse effect in canola (B. napus L.) plant.…”