Modern plant physiology achievements in the field of study of the most important group of the classic phytohormones — cytokinins have been analyzed. An emphasis is made on the two up-to-date approaches — revealing the origin and evolution of these hormones as well as their interaction with other components of the hormonal system (auxins, gibberellins, ethylene, abscisic and jasmonic acids, brassinosteroids, strigolactones). It is shown that despite the fact that cytokinins are widely spread in the biological world, their signaling fucntions have evolved only in angiosperms. Only higher plants have formed such kind of the regulation mechanism that integrates all hormonal substances in a single system. Data concerning the occurrence of close crosstalk between all components of the plant hormonal complex are presented. A leading role of the phytohormone balance in the plant physiological processes regulation is underlined.
Keywords: cytokinins, evolution, phytohormone interaction, regulation, auxins, gibberellins, abscisic acid, ethylene
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