Liu Yuanxi, Duan Guihe, Wu Junwen, Shi Rui
College of Forestry, Southwest Forestry University, Kunming, Yunnan, China.
Yunnan Provincial Key Laboratory for Conservation and Utilization of In-forest Resource, Southwest Forestry University, Kunming, Yunan, China.
Front Plant Sci. 2025 Jul 17;16:1619386. doi: 10.3389/fpls.2025.1619386. eCollection 2025.
To elucidate how seedling age affects shade adaptation mechanisms in , we conducted a light intensity experiment with 1- and 3-year-old seedlings under five light levels (100%, 80%, 45%, 30%, and 5% of full sunlight). We evaluated the root non-structural carbohydrates (NSC), carbon:nitrogen:phosphorus (C:N:P) stoichiometry, and biomass allocation using phenotypic plasticity indices and correlation analysis. Phenotypic plasticity analysis revealed distinct age-dependent strategies: 1-year-old seedlings prioritized root morphological features (biomass, surface area) and starch storage, whereas 3-year-old seedlings prioritized metabolic flexibility (soluble sugar/starch ratio, N/P balance). Correlation analyses further demonstrated age-specific resource allocation patterns; in 1-year-old seedlings, biomass was associated with the root C/P ratio and starch reserves, whereas in 3-year-old seedlings, growth was associated with soluble sugars and N metabolism. Investment in photosynthetic organs (needle biomass) was prioritized under shade in 1-year-old seedlings, which is consistent with the source-sink theory; however, the root C content of these seedlings was reduced, and their N uptake was enhanced to maintain chlorophyll synthesis. Conversely, survival was prioritized in 3-year-old seedlings by increasing the amount of structural C in roots and optimizing C:N:P stoichiometry (e.g., lower C/N ratio and higher N/P ratio), which is consistent with the C storage priority hypothesis. These findings highlight a developmental transition from growth-driven C allocation in young seedlings to survival-oriented stoichiometric adjustments in older seedlings, which provides important insights for silvicultural practices in heterogeneous light environments.
为了阐明幼苗年龄如何影响[具体树种未提及]的遮荫适应机制，我们对1年生和3年生幼苗在五种光照水平（全日照的100%、80%、45%、30%和5%）下进行了光照强度实验。我们使用表型可塑性指数和相关性分析评估了根系非结构性碳水化合物（NSC）、碳：氮：磷（C:N:P）化学计量比和生物量分配。表型可塑性分析揭示了不同的年龄依赖性策略：1年生幼苗优先考虑根系形态特征（生物量、表面积）和淀粉储存，而3年生幼苗优先考虑代谢灵活性（可溶性糖/淀粉比、N/P平衡）。相关性分析进一步证明了特定年龄的资源分配模式；在1年生幼苗中，生物量与根系C/P比和淀粉储备相关，而在3年生幼苗中，生长与可溶性糖和N代谢相关。1年生幼苗在遮荫条件下优先投资于光合器官（针叶生物量），这与源库理论一致；然而，这些幼苗的根系C含量降低，N吸收增加以维持叶绿素合成。相反，3年生幼苗通过增加根系中结构性C的含量并优化C:N:P化学计量比（例如，较低的C/N比和较高的N/P比）来优先考虑生存，这与C储存优先假说一致。这些发现突出了从幼龄幼苗中生长驱动的C分配到老龄幼苗中生存导向的化学计量调整的发育转变，这为异质光照环境下的造林实践提供了重要见解。
