Juvenile phase: an important phase of the life cycle in plants

The juvenile phase of plants refers to the period from seed germination to the period in which they gain flowering ability. The phase is vital for the breeding of new plant varieties, the study of plant stress and immune responses, and the utilization of resources. The trichome characteristics, leaf size, leaf shape, leaf base angle, and shoot apical meristem (SAM) are different in the juvenile and adult phases, and the types and contents of starch, protein, and polypeptides are also different. The duration of the juvenile phase varies greatly among plants, and woody plants usually have a juvenile phase lasting several years or decades. The duration of the juvenile phase is affected by species, temperature, light, sugars and endogenous hormones. The expression of microRNA 156 (miR156) is higher in the juvenile phase and decreases with aging, and the expression of its target gene, SQUAMOSA promoter binding protein-like (SPL), is the opposite. Overexpression of miR159 can shorten juvenile phase by indirectly inhibiting miR156 expression. Moreover, both miR157 and miR156 shorten the juvenile phase. In contrast, miR172 facilitates the juvenile-to-adult phase transition. Epigenetic modifications also affect the gene function of miR156. In addition, Flowering Locus T (FT) and Terminal Flower 1 (TFL1) are members of the phosphatidylethanolamine-binding protein (PEBP) family, play important and opposite roles in the juvenile-to-adult phase transition. In this article, the application prospects and existing problems of the juvenile phase are discussed to provide ideas for future research and regulation of the juvenile phase.