Accumulation of heavy metals and antioxidant respo

Authors: Aleksandra NadgórskaSocha Alina Kafel Marta KandzioraCiupa Janina Gospodarek Agnieszka ZawiszaRaszka

Publish Date: 2012/09/23

Volume: 20, Issue: 2, Pages: 1124-1134

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Abstract

The purpose of this study was to explore the effects of soil contamination by selected metals cadmium copper nickel lead or zinc on the antioxidant response of Vicia faba plants The levels of the antioxidants glutathione proline nonprotein thiols as well as guaiacol peroxidase and catalase activities were measured in the upperparts of plants Additionally the potential bioavailability of metals in the soil and their concentrations in V faba plants were compared Treatment with metal caused the problem of an elevation in its bioavailability in soil and its concentration in leaves and stems The most serious problems seemed to be metal elevations in soil especially Zn and Ni as well as in the aerial parts of V faba plants The antioxidant responses appeared to be metal specific The elevation of guaiacol peroxidase activity in leaves and stems as well as the proline in leaves was the only more general reaction to metal exposure Upon analysis of the effects of soil metal contamination on V faba plants we recommend the use of some measurements such as guaiacol peroxidase activity and proline level as useful tools in biological monitoringThere are multiple sources of soil contamination with heavy metals such as industrial wastes agriculture fertilizers and roadways The problem of soil contamination may be of great importance for crops grown in the vicinity of heavy industrial sites In such surroundings the uptake of metals depends on the bioavailability of metals Teklić et al 2008 The bioavailable fraction of heavy metals is an issue of particular concern from ecological toxicological and health standpoints due to the possible penetration into most environmental segments including food chains Kucharski et al 2005Heavy metals like cadmium Cd copper Cu nickel Ni lead Pb zinc Zn may affect the status of plants differently Some of them are essential elements for cellular metabolism Cu Zn Ni while some are nonessential Cd Pb Cu and Zn are constituents of many enzymes and other proteins The requirement of plants for Ni appears to be mainly related to its role in forming the active metallocentre of urease Gratão et al 2005 Page and Feller 2005The redistribution of metals within plants is metal specific Page and Feller 2005 The elevation of nonessential metals like Pb Cd and micronutrients such as Zn Cu and Ni may be the cause of several negative aspects of oxidative stress Zengin and Munzuroglu 2005 Meng et al 2007 Therefore the effectiveness of a plant’s antioxidant defense may be crucial for elucidating its tolerance mechanisms to heavy metals which are common contaminants of soil The synthesis of diverse metabolites in millimolar concentrations particularly specific amino acids such as proline and histidine and peptides such as glutathione GSH or phytochelatins PC may be important for defense mechanisms against a metal’s action Low molecular weight antioxidants such as proline ascorbic acid or glutathione detoxify oxygen free radicals Nonprotein compounds rich in –SH groups are capable of binding metal ions and forming nontoxic complexes with metals They are also involved in determining a plant’s tolerance to heavy metal ions which is another important factor Wei et al 2003 Sharma and Dietz 2006 Sun et al 2007 Xu et al 2009 The accumulation of proline a very effective singletoxygen quencher and redox active metal ions binder activates and protects enzymes such as catalase CAT and guaiacol peroxidase POD Teklić et al 2008 The latter enzyme is involved in several processes such as cell growth auxin catabolism lignifications as well as abiotic and biotic stress responses Fang and Kao 2000 Cui and Wang 2006

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