Comprehensive Phytohormone Analysis Reveals the Roles of Auxin, Cytokinin, and Gibberellin in Enhancing Seed Germination and Growth of Chimonobambusa utilis

Bamboo seeds (often called bamboo rice) are nutritionally rich, offering protein, fiber, and essential minerals like potassium and manganese. <i>Chimonobambusa utilis</i> seeds, especially, represent an underexplored nutritional resource with exceptional edible and agricultural potential. Here, we report that <i>Ch. utilis</i> seeds contain remarkably high levels of unsaturated fatty acids (67.39% of total lipids), with linoleic and linolenic acids comprising 36.5% and 26.7%, respectively, exceeding major vegetable oils by 1.5 to 3.3-fold. Comprehensive plant growth regulator (PGR) screening revealed distinct regulatory patterns: gibberellic acid (GA₃, 8.66 µM) exhibits biphasic dose-response kinetics, cytokinins (6-BA, 222.0 µM) show nonlinear responses transitioning from low-concentration inhibition to high-concentration promotion with preferential lateral root induction, while auxins (NAA, 134.2 µM) demonstrate unimodal responses with concentration-dependent efficacy, achieving the strongest root-promoting effect (27% increase, <i>p</i> < 0.05). Mechanistically, optimal phytohormone treatments sustained elevated soluble sugar levels and differentially modulated key enzymes. Notably, 6-BA potently suppressed sucrose synthase activity while NAA maximally stimulated starch biosynthetic enzyme activities (AGPase and GBSS), identifying sucrose metabolism as a pivotal regulatory node. Comparative evaluation of germination capacity and seedling vigor revealed that individual treatments with 8.66 µM GA₃, 222.0 µM 6-BA, or 134.2 µM NAA achieved the best performance among tested concentrations, reducing germination time by 5 days and increasing germination percentage by 4.2 to 6.3% relative to control. These findings establish <i>Ch. utilis</i> as a premium oil crop candidate and provide mechanistic insights into phytohormone-mediated germination control with broad implications for bamboo seed biology and propagation optimization.