Cytokinins and their sugar or non-sugar conjugates are very active growth-promoting factors in plants, although they occur at very low concentrations. These compounds have been identified in numerous plant species. This review predominantly focuses on 9-substituted adenine-based cytokinin conjugates, both artificial and endogenous, sugar and non-sugar, and their roles in plants. Acquired information about their biological activities, interconversions, and metabolism improves understanding of their mechanisms of action and functions in planta. Although a number of 9-substituted cytokinins occur endogenously, many have also been prepared in laboratories to facilitate the clarification of their physiological roles and the determination of their biological properties. Here, we chart advances in knowledge of 9-substituted cytokinin conjugates from their discovery to current understanding and reciprocal interactions between biological properties and associated structural motifs. Current organic chemistry enables preparation of derivatives with better biological properties, such as improved anti-senescence, strong cell division stimulation, shoot forming, or more persistent stress tolerance compared to endogenous or canonical cytokinins. Many artificial cytokinin conjugates stimulate higher mass production than naturally occurring cytokinins, improve rooting, or simply have high stability or bioavailability. Thus, knowledge of the biosynthesis, metabolism, and activity of 9-substituted cytokinins in various plant species extends the scope for exploiting both natural and artificially prepared cytokinins in plant biotechnology, tissue culture, and agriculture.

中文翻译：

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天然存在的人工N9细胞分裂素共轭物：从合成到生物活性再到合成。

细胞分裂素及其糖或非糖结合物是植物中非常活跃的促生长因子，尽管它们的浓度非常低。这些化合物已在许多植物物种中鉴定出来。这篇综述主要侧重于人工和内源，糖和非糖的9-取代的基于腺嘌呤的细胞分裂素结合物，以及它们在植物中的作用。获得有关它们的生物学活性，相互转化和代谢的信息可以增进对它们在植物中的作用和功能机制的了解。尽管许多9-取代的细胞分裂素是内源性发生的，但在实验室中也已经制备了许多，以帮助阐明它们的生理作用和确定其生物学特性。这里，我们绘制了9-取代细胞分裂素共轭物的知识进展，从发现到目前的了解以及生物学特性和相关结构基序之间的相互作用。与内源性或规范性细胞分裂素相比，当前的有机化学能够制备具有更好生物学特性的衍生物，例如改善的抗衰老，强大的细胞分裂刺激，枝条形成或更具持久性的胁迫耐受性。许多人工细胞分裂素缀合物比天然存在的细胞分裂素刺激更高的产量，改善生根，或仅具有高稳定性或生物利用度。因此，有关生物合成，新陈代谢，