Pb-Stress Induced Oxidative Stress Caused Alterations in Antioxidant Efficacy in Two Groundnut (<i>Arachis hypogaea</i> L.) Cultivars

Abstract

Lead (Pb) is an important environmental pollutant extremely toxic to plants and other living organisms including humans. To assess Pb phytotoxicity, a pot culture experiment was carried out using two groundnut cultivars (Arachis hypogaea L. cultivar K6 and cultivar K9) on plant growth, ROS levels, lipid peroxidation, and antioxidant metabolism using biochemical, histochemical methods. Plants were grown in pots for 14 days, in the botanic garden, and subjected to Pb-stress (0, 100, 200, 400 and 800 ppm) by adding Pb (NO3)2 solution and further allowed to grow for 10 days. The results showed that cultivar K6 registered lower Pb accumulation than cultivar K9, however, localization of Pb was greater in roots than leaves in both groundnut cultivars. The Pb-stress results in an increase in free radicals (O2• − and H2O2) generation in both groundnut cultivars, but more significantly in cultivar K9 than K6. Pb-stress also caused significant changes in the rate of peroxidation as shown in the levels of malondialdehyde (MDA) content in roots and leaves of both groundnut cultivars. Free proline, ascorbic acid (AsA) and non-protein thiol (NP-SH) contents were increased in cultivar K6 due to Pb-stress, but less in cultivar K9. Pb treated plants showed increased levels of antioxidant enzymes such as superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) glutathione reductase (GR) and glutathione Stransferase (GST). Isozyme band intensities of SOD, GPX and APX were more consistent with the respective changes in antioxidative enzyme activities. These results indicate that cultivar K6 possesses greater tolerance potential for Pb toxicity than cultivar K9.

Expression Analysis of WRKY Transcription Factor Genes in Response to Abiotic Stresses in Horsegram (<i>Macrotyloma uniflorum</i> (Lam.) Verdc.)

“…However, the level of MDA is more in salt stress than in drought stress conditions (Figure 3). An increase in the MDA concentration under abiotic stress conditions like Pb stress was previously reported in groundnut plants by Nareshkumar et al [25]. …”

In-situ localization and biochemical analysis of bio-molecules reveals Pb-stress amelioration in Brassica juncea L. by co-application of 24-Epibrassinolide and Salicylic Acid

“…100 who reported lowered GSH in Gongauloux polyedea exposed to Pb stress. The decline in GSH levels is due to lowered de-novo production of GSH as well as over-utilization of GSH in the synthesis of phytochelatins, pre-requisite for chelation of toxic metal ions 101 . This antioxidant fortifies protein oxidation and acts as a substrate for production of glutathione peroxidase and glutathione-S-transferase 102 .…”

Foliar application of salicylic acid improves growth and yield attributes by upregulating the antioxidant defense system in Brassica campestris plants grown in lead-amended soils

“…When plants are under Pb stress, several physiological processes are disrupted by the production of increased amounts of reactive oxygen species (ROS) leading to oxidative stress within the plant cells so inhibiting photosynthetic activity, chlorophyll (chl) biosynthesis, hormonal balance, ion homeostasis, membrane stability, ATP production, lipid peroxidation, DNA damage, and imbalances in nutrient and water relations resulting in cell abnormalities and death [5][6][7]. Plants deal with Pb toxicity by different physiological and biochemical processes.…”