Molecular Plant Breeding 2024, Vol.15, No.6, 328-339 http://genbreedpublisher.com/index.php/mpb 330 Zahedi et al. (2019) observed that foliar application of Se-NPs not only improved growth parameters in strawberries but also increased the levels of osmotic regulators such as total soluble carbohydrates and free proline. This treatment enhanced the activity of antioxidant enzymes and reduced lipid peroxidation and hydrogen peroxide (H2O2) accumulation, significantly improving salt stress tolerance. Moreover, low concentrations of Se-NPs (10 μM) were found to mitigate the loss of calcium and potassium, boost catalase activity, increase phenolic compound content, and improve photosynthesis and antioxidant capacity (Soleymanzadeh et al., 2020). Further research by Pourebrahimi et al. (2023) demonstrated that the combined application of sodium selenate (Na2SeO4) and hydrogen sulfide (NaHS) significantly enhanced selenium concentration, antioxidant system activity, and flavor quality in strawberry fruits. These findings suggest that appropriate doses of Se-NPs or selenium compounds can not only alleviate the negative impacts of salt stress on strawberries but also improve fruit quality by enhancing antioxidant capacity and photosynthetic efficiency. 2.2 Mechanisms of selenium in alleviating heavy metal stress Heavy metal pollution is one of the major abiotic stresses limiting strawberry productivity. Studies have shown that exogenous selenium supplementation can alleviate the toxicity of heavy metals such as cadmium (Cd) and lead (Pb) in strawberries by restricting metal ion uptake at the root level, reducing the translocation of metals to aboveground tissues, and enhancing antioxidant responses (Hasanuzzaman et al., 2022). Zhang et al. (2011) found that foliar application of sodium selenite (Na2SeO3) not only reduced the absorption of Cd and Pb but also maintained cell membrane stability by lowering the content of malondialdehyde (MDA), a lipid peroxidation product. Similarly, Zhang et al. (2020) demonstrated that low concentrations of Na2SeO3 significantly enhanced the activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), reducing Cd accumulation and thereby improving the growth performance and fruit quality of strawberries. Moreover, selenium effectively alleviates oxidative damage and photosynthetic inhibition caused by Cd stress (Song et al., 2024). A meta-analysis by Tian et al. (2024) further revealed that the effectiveness of selenium in mitigating heavy metal stress is closely related to its application concentration, plant species, and soil conditions. Through its multifaceted regulatory mechanisms, selenium significantly reduces the toxic effects of heavy metals on strawberries, providing new possibilities for sustainable strawberry production in polluted soil environments. 2.3 Role of selenium in alleviating drought stress Drought is another critical factor limiting strawberry yield and quality, and selenium has shown significant potential in enhancing plant drought tolerance. Studies have demonstrated that Se and Se-NPs can mitigate the adverse effects of drought on strawberries by enhancing antioxidant enzyme activity, improving WUE, and stabilizing cell membranes (Ahmad et al., 2016; Dar et al., 2021). For instance, Zahedi et al. (2020) investigated the potential of SiO2-NPs, Se-NPs, and Se/SiO2-NPs in mitigating the negative impacts of drought on strawberry growth and yield. The results showed that exogenous application of Se/SiO2-NPs significantly increased carbohydrate and proline content as well as the activity of the antioxidant system, thereby enhancing drought tolerance and fruit quality in strawberries. Furthermore, Wang et al. (2022) found that treatment with selenomethionine (Se-Met) not only improved photosynthesis and water status in strawberries but also significantly increased soluble solids, sugar-to-acid ratio, and vitamin C content in the fruits. Liu et al. (2024) further reported that the combined application of Se-NPs and copper nanoparticles (Cu-NPs) markedly improved photosynthetic pigment content and chlorophyll fluorescence parameters under drought conditions, while also optimizing fruit quality. These findings indicate that selenium has considerable potential in alleviating drought stress in strawberries, providing essential insights for enhancing the adaptability and yield of strawberries in arid environments. 3 Effects of Selenium on Strawberry Quality 3.1 Enhancing the nutritional value of strawberries Selenium biofortification has proven highly effective in enhancing the nutritional value of strawberries. Studies
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