Nanoscale Zerovalent Iron Based Moderation of Chromium Stress in Tomato Seedlings is Related with Induced Antioxidants and Suppressed Cr Uptake

Abstract

The nanoscale zerovalent iron (nZVI) has been widely used in remediation of environmental pollutants from the aqueous as well as soil media. The present study was conducted to evaluate the role of nZVI as a soil amendment in amelioration of chromium (Cr) toxicity in tomato seedlings. Three weeks exposure with low (10 mg kg-1) and high (100 mg kg-1) Cr(VI) was given to tomato seedlings grown in soil medium supplemented with or without 500 mg kg-1 nZVI in corresponding soils. The Cr exposure greatly reduced the biomass with high Cr(VI) lowering the plant height, root length, shoot and root biomass by 34, 24, 33 and 49%, respectively. However, nZVI significantly restored the growth retardation by increasing these parameters by 17, 14, 19 and 33%, respectively. The nZVI also lowered the Cr-induced MDA content, improved membrane stability index and increased relative water contents. The nZVI was also effective in improving the chlorophyll pigments and carotenoids contents. The antioxidant enzymes (viz. SOD, POD, CAT and APX) were slightly increased by Cr stress. The nZVI application together with Cr stressed soil further enhanced these enzyme activities. Application of nZVI further lowered the significant amount of Cr(VI) in shoots and roots tissues. The nZVI-induced tissue Cr concentration was lowered by 35% in shoots in case of low Cr exposure and 29% in roots by high Cr treatments. The amelioration of Cr-induced toxicity in tomato seedlings by nZVI application in soil seems to be the result of suppression of Cr uptake and enhancement in antioxidant enzyme system.