Defense manifestations of enzymatic and non-enzymatic antioxidants in Ricinus communis L. exposed to lead in hydroponics

Abstract

Lead (Pb) is a major inorganic pollutant with no biological significance and has been a global concern. Phytotoxicity of lead induces toxic effects by generating reactive oxygen species (ROS), which inhibits most of the cellular processes in plants. Hydro-ponic experiments were performed with Ricinus communis to investigate the toxicity and antioxidant responses by exposing to different concentrations of lead (0, 200 and 400 µM) for 10 days. Pb stress caused a significant increase in electrolyte leakage, non-enzymatic antioxidants (phenols and flavonoids) and a decrease in the elemental profile of the plant. Histochemical visualization clearly indicates the significant increase of H2O2 production in dose-dependent manner under Pb stress. Likewise, an increase in catalase, guaiacol peroxidase and superoxide dismutase activity was also evident. Ascorbate peroxidase and MDAR, on the other hand, responded biphasically to Pb treatments showing a decrease in concentration. The decline in redox ratio GSH/GSSG was imposed by the indirect oxidative stress of Pb. Hence these findings showed the ameliorative potential of R. communis to sustain Pb toxicity under oxidative stress.

Biofuel Production with Castor Bean: A Win–Win Strategy for Marginal Land

“…According to this, arbuscular mycorrhizal fungal treatments significantly influenced rhizosphere soil pH, Pb bioavailability, and CB shoot Pb concentration [46]. Amendments, such as biochar or rice husk ash, can be used in mitigating Pb toxicity, improving plant growth, and decreasing Pb accumulation in roots up to 59% by immobilizing Pb [61]. Among the chelates, citric acid can remove 17-fold more Pb than untreated plants [37], while improving photosynthesis and plant growth [62].…”

The utilization of Ricinus communis in the phytomanagement of heavy metal contaminated soils

“…The level of oxidative damage in plants can be determined by malondialdehyde (MDA), which is regarded as a component of lipid peroxidation (Zu et al 2016). Several studies have revealed that the exposure of R. communis to higher concentrations of toxic metals did not significantly (p > 0.05) increase the MDA level in different parts of this plant, signifying that R. communis has the capability to tolerate metal stress to a certain extent (Bauddh and Singh 2012;Bauddh et al 2016;Kiran and Prasad 2019a;Pal et al 2013). A comparative study revealed that accumulation of MDA in root (3.36-fold) and leaves (4.53-fold) of B. juncea was higher than that in the roots (2.8-fold) and leaves (2.8-fold) of R. communis when treated with Cd.…”

“…Recently, Khan et al (2018) reported that increasing concentrations of Pb (0, 100, 200, and 500 mol•L −1 ) increased H 2 O 2 and MDA content in R. communis and decreased H 2 O 2 and MDA content in B. mutica, which was attributed to a special defense mechanism in B. mutica. Kiran and Prasad (2019a) reported that elevated levels of Pb significantly (p < 0.05) increased H 2 O 2 levels and decreased monodehydroascorbate reductase (MDAR) levels in R. communis when compared with a control under Pb stress.…”

“…These are produced in stressed plants in response to the overproduction of ROS, and their regulation influences stress tolerance. The antioxidants thus produced can eliminate or regulate ROS production and enhance plant growth under stressful environments (Kiran and Prasad 2019a). Various studies have evaluated antioxidant activity in R. communis under metal stress (Bauddh et al 2016;Khan et al 2018; Kiran and Prasad 2019a).…”

“…To combat metal stress, plants possess various defense mechanisms such as antioxidant enzyme production, sequestration or compartmentalization of metals in metabolically inactive parts of the plant, and organic acid exudation that enhances the plant's tolerance against metal stress (Huang et al 2016; Kiran and Prasad 2019a;Ren et al 2020). Several stress-responsive genes have also been identified to aid in stress tolerance.…”