Panax ginseng, a perennial medicinal plant, utilizes its dried roots and rhizomes for medicinal purposes. Currently, in China, ginseng cultivation employs two methods: under-forest and farmland planting. These methods create distinct habitats, significantly influencing the ginseng's rhizome morphology and, consequently, its economic value. In this study, two-year-old ginsengs were transplanted into farmland (TCG), a larch forest (TLCG) and a Quercus mongolica forest (TQCG) to analyze the differences in rhizome phenotypes caused by habitat changes. The results showed that there were significant differences in light intensity and the soil's available phosphorus and potassium contents between farmland and forest environments. The differences in habitats led to different adaptability of the ginseng's rhizome morphology. Compared with TCG, the rhizomes of TLCG and TQCG were significantly elongated by 48.36% and 67.34%, respectively. After the rhizomes' elongation in TLCG and TQCG, there was an increase in indole-3-acetic acid (IAA) contents and a decrease in lignin contents. By analyzing the expression of key genes, we found that, compared with TCG, the expression of key enzymes of lignin biosynthesis genes such as PgCOMT and PgCCR4 were down-regulated. The difference in ginseng's rhizome length is related to the signal transduction pathway of auxin and gibberellin. In addition, we preliminarily screened out transcription factors PgWRKY75, PgDIV, and PgbHLH93.1, which can actively respond to habitat changes and play important roles in the elongation of ginseng rhizomes. In summary, this study elucidates the phenotypic plasticity strategy of ginseng rhizomes in response to habitat changes and delineates the regulatory mechanism behind phenotypic adaptation, offering novel insights into ginseng's morphogenesis.
Keywords: Panax ginseng; endogenous hormone; habitat change; lignin; phenotypic plasticity; rhizome.