Journal
TOXICS
Volume 10, Issue 1, Pages -Publisher
MDPI
DOI: 10.3390/toxics10010036
Keywords
phytotoxicity; clary sage; chlorophyll fluorescence; photosynthesis; reactive oxygen species; hydroponic culture; redox state; quinone A (Q(A)); non photochemical quenching; hydrogen peroxide
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The study evaluates the mitigative role of excess zinc (Zn2+) supply in the uptake, translocation, and toxicity of cadmium (Cd2+) in clary sage. Excess zinc application reduced cadmium uptake and translocation, restored chloroplast structure, and improved photosystem II photochemical efficiency in clary sage plants.
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 mu M CdSO4) alone, and in combination with Zn2+ (900 mu M 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 (phi(PSII)) 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.
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