Selenium (Se), an essential micronutrient for humans, is also a beneficial nutrient for growth and development of many plants. The aim of the present study was to determine whether low-dose Se application could increase plum growth and serotonin synthesis, as well as upregulate the glutathione redox cycle. Two-year-old plum trees were treated with Se 6+ (Na 2 SeO 4 ) and Se 2− (SeMet). Growth parameters, levels of serotonin synthesis precursors, compounds and enzymes of the glutathione (GSH) redox cycle, and the antioxidant capacity were analyzed. Results showed that plant height and stem diameter were increased by Se treatment. The leaf Se content was significantly increased; tryptophan was not affected by Se treatment, while the 5-hydroxytryptophan content was significantly higher than control. Although serotonin levels were also increased, the effect was not significant, and no tryptamine was detected in our study. On the 30th day, the MDA content in Se 2− was highest followed by the control and Se 6+ treatment, and the activities of T-AOT and CAT were increased, while GST was reduced by Se treatment. The two forms of Se treatments increased the activity of GPX and GR, and the total content of GSH + glutathione disulfide (GSSG) at the end of treatment. Furthermore, the level of GSH and GSH/GSSG was instable changed. GSSG content was similar during the treatment time except on the 20 days. Conclusively, the pathway of plum serotonin was clear, both Se 6+ and Se 2− could influence the serotonin synthesis. Additionally, the GSH redox cycle was sensitive to the Se application. Moreover, Se 6+ performed better than Se 2− on leaf Se content, plant growth parameters, and antioxidant capacity.

中文翻译：

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硒对李子叶血清素合成及谷胱甘肽氧化还原循环的影响

硒 (Se) 是人类必需的微量营养素，也是许多植物生长发育的有益营养素。本研究的目的是确定低剂量硒应用是否可以促进李子生长和血清素合成，以及上调谷胱甘肽氧化还原循环。用Se 6+ (Na 2 SeO 4 ) 和Se 2- (SeMet) 处理两年生李树。分析了生长参数、血清素合成前体的水平、谷胱甘肽 (GSH) 氧化还原循环的化合物和酶以及抗氧化能力。结果表明，硒处理增加了株高和茎粗。叶片硒含量显着增加；色氨酸不受硒处理的影响，而5-羟色氨酸含量显着高于对照。虽然血清素水平也有所增加，效果不显着，在我们的研究中没有检测到色胺。第30天，Se 2- 中MDA含量最高，其次是对照和Se 6+ 处理，T-AOT和CAT活性增加，而GST则被Se处理降低。两种形式的硒处理均增加了 GPX 和 GR 的活性，以及​​处理结束时 GSH + 谷胱甘肽二硫化物 (GSSG) 的总含量。此外，GSH和GSH/GSSG的水平发生了不稳定的变化。除 20 天外，处理期间 GSSG 含量相似。结论是，李子血清素的途径是明确的，Se 6+ 和Se 2- 都可以影响血清素的合成。此外，GSH 氧化还原循环对硒的应用很敏感。此外，Se 6+ 在叶片硒含量、植物生长参数、