Cytokinins are a class of plant hormones that promote cell division, induce shoot formation, and promote their growth. Translated as cytokinin. The term cytokinein comes from cytokinesis (cell division). Mainly distributed in the parts of cell division, such as shoot tips, root tips, immature seeds, germinated seeds, and inside of growing fruits.
It was also called "cytokinin" when it was first discovered. is a type of plant hormone. In 1955, when Skoog and others in the United States were studying plant tissue culture, they discovered a substance that promotes cell division, which was named kinetin. Its chemical name is 6-furfurylaminopurine (KT), the pure product is white solid and can be dissolved in strong acid and alkali. Kinetin does not exist in plants. After that, more than a dozen substances with the physiological activity of kinetin were isolated from plants. Now all substances with the same physiological activity as kinetin, whether natural or synthetic, and synthetic plant growth regulators, are collectively referred to as cytokinins.
Their basic structure has a 6-aminopurine ring. The natural cytokinins in plants are zeatin (ZT), dihydrozeatin, isopentenyl adenine, zeatin riboside, isopentenyl adenosine, etc. The site where they are synthesized in the body is mainly the root tip. In addition to kinetin, synthetic cytokinins include 6-benzylaminopurine (6-BA).
There are two most obvious physiological roles of cytokinin: one is to promote cell division and regulate its differentiation. In tissue culture, the ratio of cytokinin and auxin affects the differentiation of plant organs. Usually, when the ratio is high, it is conducive to the differentiation of shoots; when the ratio is low, it is conducive to the differentiation of roots. The second is to delay the degradation of protein and chlorophyll and delay aging.
There are differences in the activity of various cytokinins. For example, in growth-promoting biological assays, natural cytokinins such as zeatin, isopentenyl adenine are more active than synthetic cytokinins such as 6-benzylaminopurine and agonist. In the biological test of delaying the decomposition of chlorophyll, the activity of the latter is higher than that of the former.
