Phytohormones: Structure, Physiological Effects, and Hormone Interactions of Classical and Newly Discovered Plant Growth Regulators
Mehmet Sezgin1,2,*, Mustafa Kahya2
1 Çankırı Karatekin University Food and Agriculture Vocational School, Çankırı, Türkiye
2 Department of Biology, Çankırı Karatekin University Graduate Education Institute, Çankırı, Türkiye
* Corresponding Author: Mehmet Sezgin. Email: 
Phyton-International Journal of Experimental Botany https://doi.org/10.32604/phyton.2026.087624
Received 19 June 2026; Accepted 06 August 2026; Published online 20 August 2026
Abstract
Plants utilize a complex network of phytohormones to adapt to environmental stressors and coordinate their growth and development. Along with the classic five hormones (auxin, cytokinin, gibberellin, abscisic acid, and ethylene), newly discovered classes of hormones such as brassinosteroids, salicylic acid, jasmonic acid, strigolactones, karrikins, and peptide hormones regulate almost all aspects of plant physiology. This review article has been prepared with the needs of researchers and practitioners involved in plant production in mind. Phytohormones are systematically discussed in terms of their discovery history, chemical structures, fundamental roles in plant physiology, and interhormone interactions. Each hormone class is examined under four main headings: discovery and historical development, chemical structure and types, physiological effects, and interactions with other hormones. This study aims to provide a practical, up-to-date reference for decision-making in agricultural applications, without getting bogged down in complex molecular mechanisms. Emphasis is placed on stress tolerance, growth-defense balance, and hormone crosstalk.
Keywords
Abscisic acid; auxin; brassinosteroid; cytokinin; ethylene; gibberellin; jasmonic acid; karrikin; peptide hormones; plant physiology; salicylic acid; stress tolerance; strigolactone
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