Plant-Microbe Interactions in Agro-Ecological Perspectives by Dhananjaya Pratap Singh Harikesh Bahadur Singh & Ratna Prabha

Author:Dhananjaya Pratap Singh, Harikesh Bahadur Singh & Ratna Prabha
Language: eng
Format: epub
Publisher: Springer Singapore, Singapore

15.4 Molecular Basis of Phytoremediation and Rhizoremediation

15.4.1 Reactive Oxygen Species (ROS), Reactive Nitrogen Species (RNS) and Heavy Metal Tolerance

Stress induced by HMs in plants actuates the immediate or aberrant creation of ROS, (e.g. superoxide radicals, hydrogen peroxide along with hydroxyl radicals) and reactive nitrogen species (RNS) subsequently prompting to oxidative pressure in plants (Anjum et al. 2012; Kruszka et al. 2012). Oxidative stress is a multifarious physiological and chemical process that creates as a consequence of overproduction and amassing of responsive oxygen species (ROS) in reaction to biotic as well as abiotic stresses inside higher plants (Demidchik 2015). ROS accumulation causes oxidative harm en route for nucleic acids, proteins and lipid bilayer. One of the systems of HM resilience is detoxification of ROS mediated by antioxidant compounds and antioxidant enzyme systems (Variyar et al. 2014). Antioxidants form sophisticated intracellular as well as extracellular networks ensuring protection against oxidation and thus shape stress signalling (Demidchik 2015). In plants, oxidative stress is neutralized by secretion of enzymes, for example, superoxide dismutases, catalases and peroxidises in addition to non-enzymatic foraging mechanisms including ascorbate, glutathione, carotenoids, xanthophylls, tocopherol, etc. (Kruszka et al. 2012).

Tripeptide glutathione (GSH, γ-Glu-Cys-Gly) is reported to secure plants against oxidative stress provoked by HMs and metalloids and comprises of both immediate and aberrant control of reactive oxygen species in addition to their reaction products in cells (Anjum et al. 2012). Also, a few GSH-related chemicals, for example, GSH reductase, GSH peroxidases and GSH sulfotransferases frame a productive framework to ensure plant protection against ROS-incited impacts. Furthermore, glutathione and related catalysts likewise assume noteworthy part in detoxification, chelation and compartmentalization of HMs and metalloids in plants (Anjum et al. 2012). Furthermore, ROS and H2O2 are important signalling molecules as they act as agents for the initiation of genes defending against HM-induced stress (Foyer and Noctor 2005; Noctor et al. 2012). Redox signalling molecules allow and induce a series of appropriate physiological processes and produce particular signals incorporated with the action of plant hormones, for example, salicylic acid, ethylene, abscisic acid and jasmonates (Bartoli et al. 2013). SODs (superoxide dismutases) assume principal roles in the stress reaction by changing over the very lethal superoxide radicals (O2−) into less harmful hydrogen peroxide (Kruszka et al. 2012). Nitric oxide (NO) is likewise perceived as a key controller of plant physiological procedures. Several components of signalling pathways have been portrayed that communicate NO effects in plants, including second messengers, protein kinases, phytohormones and target genes, etc. (Astier et al. 2012).s Redox and hormone signalling pathways within plants shape an incorporated network of redox-hormones that manages plant development and protection pathways. The focal components of the thiol-disulphide redox administrative centre point of plant cells include glutathione, peroxiredoxins, glutaredoxins, thioredoxins and NADPH-thioredoxin reductases. These are the key controllers for some pathways and reactions related to the signalling of heavy metal stress (Noctor et al. 2012). It has been reported in earlier studies that Cd is maintained and detoxified inside the roots by chelation by way of thiol compounds in addition to subsequent sequestration (Yan and Zhang 2013).

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