Selenium (Se) is an essential element in mammals; however, there is frequently an insufficient intake due to several factors. Different techniques have been used to deal with this problem, such as plant biofortification with Se in its ionic forms and, more recently, at the nanoscale. Additionally, despite the fact that Se is not considered an essential element in plants, it has been shown to stimulate (through still unknown mechanisms) plant metabolism, causing an increase in the synthesis of molecules with reducing power, including enzymes such as glutathione peroxidase, catalase and ascorbate peroxidase as well as non-enzymatic antioxidants such as phenolic compounds, glucosinolates, vitamins and chlorophylls. A positive correlation has also been shown with other essential elements, achieving an increase in tolerance to environmental adversities. This article describes the advances made in the field of the biofortification of horticultural crops with ionic Se and nanoselenium (nSe) from 2009 to 2019. The aspects covered include various concentrations used, the findings made regarding the impact these chemical forms have on plant metabolism, and indications of its participation in the synthesis of primary and secondary metabolites that increase stress tolerance.

中文翻译：

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离子硒和纳米硒作为植物代谢的生物促进剂和刺激剂

硒（Se）是哺乳动物的必需元素。但是，由于多种因素，摄入量经常不足。已经使用了不同的技术来解决这个问题，例如用离子形式的硒和最近的纳米级植物对植物进行生物强化。此外，尽管事实上硒不是植物中必需的元素，但已显示出它可以刺激植物的代谢（通过未知的机制），从而导致具有降低能力的分子（包括谷胱甘肽过氧化物酶等）的合成增加，过氧化氢酶和抗坏血酸过氧化物酶，以及非酶抗氧化剂，例如酚类化合物，芥子油苷，维生素和叶绿素。与其他基本要素也显示出正相关，从而增加了对环境逆境的容忍度。