The transition of plants from aquatic to terrestrial environments imposed unprecedented ecological and physiological challenges, necessitating the evolution of sophisticated perception and response mechanisms. Phytohormones played a central role in this adaptive transition by orchestrating coordinated physiological and morphological adjustments that improved survival under variable terrestrial conditions. In this review, we examine the evolutionary origin, diversification, and functional specialization of the ten classical phytohormones: auxins, cytokinins (CKs), gibberellins (GAs), abscisic acid (ABA), ethylene (ETH), jasmonates (JAs), salicylic acid (SA), strigolactones (SLs), brassinosteroids (BRs), and peptide hormones (PEPs) from algal ancestors of land plants to angiosperms. The timing of the emergence of each hormonal signaling system is considered in parallel with the evolving ecological and physiological demands of terrestrial habitats, highlighting their roles in environmental sensing, stress responses across lineages, and the successful colonization and adaptation to land. Furthermore, we discuss how the sequential establishment and integration of these networks increased physiological complexity, coordinated growth and development, and provided competitive advantages under fluctuating conditions, highlighting the central role of integrated hormonal signaling in the evolutionary success of land plants.
Arabia et al. (Fri,) studied this question.