Abstract
Contamination of soils with cadmium (Cd) and lead (Pb) has emerged as a serious environmental issue that reduces crop productivity. However, the metals tolerance and accumulation potential of quinoa (Chenopodium Quinoa Willd) under the combined stress of Cd and Pb has not yet been explored. In the present hydroponic study, the physiological and biochemical characteristics of quinoa exposed to Cd and Pb were explored. Four-week-old plants of quinoa genotype ‘Puno’ were grown under different concentrations of Cd (0, 50 and 100 µM), Pb (0, 250 and 500 µM) alone as well as in combinations. The results showed that with increasing Cd and Pb levels in the nutrient solution, the plant biomass, stomatal conductance and chlorophyll contents were decreased. However, the concurrent application of higher concentrations of Cd (100 µM) and Pb (500 µM) caused even more reduction in the plant biomass (more than 50% than the control) and physiological attributes. The combined application of Pb and Cd caused oxidative stress through an overproduction of H2O2 (10-fold) and TBARS (12.5-fold), leading to decrease in membrane stability (52%). The oxidative stress was alleviated by a 7-fold, 10-fold and 9-fold overactivation of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), respectively. An excessive uptake of Cd resulted in a limited uptake of Pb and K in the roots and shoots of quinoa plants. The Cd and Pb tolerance and uptake potential of Puno showed its ability to stabilize Cd and Pb in co-contaminated soils.
Highlights
In recent times, various human activities, such as mining, the release of effluents from industries, rapid urbanization and agricultural practices, have increased cadmium (Cd) and lead (Pb) contamination in soils [1,2]
The growth of quinoa significantly declined as the contamination levels of Cd and Pb were augmented in the growth medium
Our results demonstrated that the quinoa genotype ‘Puno’ has differential tolerance and uptake potentials regarding Cd and Pb under the co‐contamination of both metals
Summary
Various human activities, such as mining, the release of effluents from industries, rapid urbanization and agricultural practices, have increased cadmium (Cd) and lead (Pb) contamination in soils [1,2]. Cadmium is very toxic even at very low concentrations, so, the uptake of Cd by plants affects their growth and normal metabolic activities [6]. Various abnormalities, such as stunted plant growth, damage to pigments and the obliteration of cell membranes and organelles, have been reported under Cd stress [3,7]. The main ROS which are deleterious to plants include singlet oxygen (1⁄2O2), superoxide (O2−), hydrogen peroxide (H2O2) and hydroxyl (HO) radicals [9,10] These ROS have ill effects on macromolecules such as lipids, proteins, carbohydrates and nucleic acids [8,11]. These ROS are detoxified in plants by antioxidant enzymes, namely, catalase (CAT), peroxidase (POD) and super‐
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