Excess Zinc Supply Reduces Cadmium Uptake and Mitigates Cadmium Toxicity Effects on Chloroplast Structure, Oxidative Stress, and Photosystem II Photochemical Efficiency in Salvia sclarea Plants

Abstract

Salvia sclarea L. is a Cd2+ tolerant medicinal herb with antifungal and antimicrobial properties cultivated for its pharmacological properties. However, accumulation of high Cd2+ content in its tissues increases the adverse health effects of Cd2+ in humans. Therefore, there is a serious demand to lower human Cd2+ intake. The purpose of our study was to evaluate the mitigative role of excess Zn2+ supply to Cd2+ uptake/translocation and toxicity in clary sage. Salvia plants were treated with excess Cd2+ (100 μM CdSO4) alone, and in combination with Zn2+ (900 μM ZnSO4), in modified Hoagland nutrient solution. The results demonstrate that S. sclarea plants exposed to Cd2+ toxicity accumulated a significant amount of Cd2+ in their tissues, with higher concentrations in roots than in leaves. Cadmium exposure enhanced total Zn2+ uptake but also decreased its translocation to leaves. The accumulated Cd2+ led to a substantial decrease in photosystem II (PSII) photochemistry and disrupted the chloroplast ultrastructure, which coincided with an increased lipid peroxidation. Zinc application decreased Cd2+ uptake and translocation to leaves, while it mitigated oxidative stress, restoring chloroplast ultrastructure. Excess Zn2+ ameliorated the adverse effects of Cd2+ on PSII photochemistry, increasing the fraction of energy used for photochemistry (ΦPSII) and restoring PSII redox state and maximum PSII efficiency (Fv/Fm), while decreasing excess excitation energy at PSII (EXC). We conclude that excess Zn2+ application eliminated the adverse effects of Cd2+ toxicity, reducing Cd2+ uptake and translocation and restoring chloroplast ultrastructure and PSII photochemical efficiency. Thus, excess Zn2+ application can be used as an important method for low Cd2+-accumulating crops, limiting Cd2+ entry into the food chain.

Role of calcium and magnesium on dramatic physiological and anatomical responses in tomato plants

“…Oxidative stress caused by calcium and magnesium deficiency led to severe disruption to plant cells and increased the contents of MDA and H2O2 in the leaves of tomato plants. These findings are in harmony with (Li et al, 2018;Sperdouli et al, 2022). The MDA and H2O2 contents showed significant alteration in response to Lebosol-Ca and Mg as their activity was found to be increased.…”

Principles and Applicability of Integrated Remediation Strategies for Heavy Metal Removal/Recovery from Contaminated Environments

“…Higher toxicity slows down plant growth, resulting in plant necrosis (Pramanick et al 2022). Poisoning plants with cadmium prevents carbon fixation and lowers chlorophyll concentrations and photosynthetic activity, negatively affecting plants (Sperdouli et al 2022). Soil Cd reduces physiological activity such as stomatal conductance, leaf water content, and transpiration, resulting in plants' osmotic stress and physiological impairment (Javad et al 2022).…”

“…First, transport toxic metal ions across physiological barriers to areas where they are concentrated; then form stable complexes with these ions, which are non-toxic and aid in their excretion. Finally, chelation complexes are formed that are non-toxic and aid in their excretion from the site of deposition (Sperdouli et al 2022).…”

Cadmium Caused Different Toxicity to Photosystem I and Photosystem II of Freshwater Unicellular Algae Chlorella pyrenoidosa (Chlorophyta)

“…Among heavy metals, cadmium (Cd) is a highly toxic element for plants and humans [ 4 ]. Cd exposure causes the inhibition of growth and decrease of the yield of crops [ 5 ], and Cd decreases photosynthetic activity by decreasing the pigment content and stomatal conductance, with the destruction of chlorophyll structure and the direct toxicity of reactive oxygen species (ROS) [ 4 , 6 ].…”