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JOURNAL OF APPLIED RESEARCH ON MEDICINAL AND AROMATIC PLANTS
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Abstract: |
Many human activities, including waste disposal and the use of synthetic phosphate fertilizers, increase the
concentration of cadmium (Cd) in the environment and harm plants and human health. Therefore, it is imperative to fnd effective solutions to overcome this problem. As plant biostimulants, trans-zeatin-type cytokinin (trZ) and silymarin (Sm) can act as anti-heavy metal agents, effectively ameliorating Cd damage to plants. In a pot
trial, the impacts of foliar treatment with tr-Z (40 μM), Sm (400 μM), or tr-Z + Sm (25 +250 μM, respectively,
applied sequentially) on biomass production, yield, photosynthetic effciency, osmoregulators, antioxidative
defense system, and transcript levels of enzyme-related genes of chili pepper under normal or Cd (500 μM) stress
were investigated. Cadmium stress elevated the levels of superoxide (O2 •–), hydrogen peroxide (H2O2), electrolyte leakage (EL), malondialdehyde (MDA), and Cd, while negatively affecting biomass production, photosynthetic effciency, and defense system components. Exogenous tr-Z and/or Sm attenuated the Cd-induced
negative impacts on plants, highlighting that the integrative tr-Z + Sm treatment was more effcient than the
single treatments. The tr-Z + Sm treatment decreased contents of roots, shoot, and fruit Cd by 66–91%, and
reduced levels of O2 •– and H2O2, MDA, and EL by 45%, 73%, 51%, and 72%, respectively, correlated with
increased tr-Z and Sm contents by 38–66%. Exogenous tr-Z + Sm increased biomass production by 99–134%,
photosynthetic effciency attributes by 31–169%, and antioxidants (ascorbate, proline, glutathione, and phenolics) by 33–123%. The levels of proteins and total leaf and fruit capsaicin were higher in Cd-stressed plants
treated with tr-Z + Sm. Furthermore, the co-application of tr-Z + Sm up-regulated the activities of superoxide
dismutase (SOD), glutathione reductase (GR), ascorbate peroxidase (APX), and catalase (CAT) enzymes by
38–43%, and maximized transcript level of genes-encoding enzymes in stress-exposed plants. As a result, the
integrative tr-Z + Sm treatment is highly recommended to mitigate Cd stress impacts in chili pepper plants
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