Magnesium nutrition is vital for the allocation of photosynthates, which serve as the material basis for quality compounds metabolism and shoots / roots growth. To analyze the effects of magnesium on the growth of tea plant and allocation of photosynthates, we explored changes in tea plant phenotype, starch content, and metabolic products based on three levels of magnesium. The results show that adequate magnesium nutrition can increase the diameter of metaxylem cells in tea plant root tips, resulting in a larger average root length and diameter. Mild Mg deficiency inhibits the transport of photosynthates from mature leaves to new shoots, leading to the accumulation of substances such as galactopyranosylxylose and arabinopyranosyl - glucopyranose in mature leaves. This consequently suppresses the transport of photosynthates to new shoots. In contrast, complete (sever) magnesium deficiency leads to the accumulation of photosynthates in stems and new shoots, inhibiting their transport to roots. For example, among the ten saccharide metabolites detected in stems and new shoots, d-Trehalose, d-Lactose, and 3′-Fucosyllactose exhibited the highest levels in incomplete magnesium supply conditions. The responses to sever and mild magnesium deficiency were observed to differ. In particular, sever magnesium deficiency inhibited the transport of photosynthates to roots, leading to their accumulation in tea plant stems, while mild magnesium deficiency inhibited their transport to new shoots, resulting in their accumulation in mature leaves. This study clarifies the metabolic changes in the quality components of tea plants under mild and sever magnesium deficiency conditions, which is conducive to improving tea quality.

中文翻译：

---

缺镁通过调节茶树光合产物的分布对根系生长和芽代谢产生差异化影响


镁营养对于光合产物的分配至关重要，光合产物是优质化合物代谢和芽/根生长的物质基础。为了分析镁对茶树生长和光合产物分配的影响，我们基于镁的三个水平探讨了茶树表型、淀粉含量和代谢产物的变化。结果表明，充足的镁营养可以增加茶树根尖中后木质部细胞的直径，从而导致平均根长和直径更大。轻度镁缺乏抑制光合产物从成熟叶到新芽的运输，导致吡喃半乳糖基木糖和阿拉伯吡喃糖基 - 吡喃葡萄糖等物质在成熟叶中积累。因此，这抑制了光合产物向新芽的运输。相反，完全（严重）镁缺乏导致光合产物在茎和新芽中积累，抑制它们向根的运输。例如，在茎和新芽中检测到的 10 种糖类代谢物中，d-海藻糖、d-乳糖和 3′-岩藻糖基乳糖在不完全镁供应条件下表现出最高水平。观察到对严重和轻度镁缺乏的反应不同。特别是，严重的缺镁抑制了光合产物向根系的运输，导致它们在茶树茎中积累，而轻度缺镁抑制了它们向新芽的运输，导致它们在成熟叶片中积累。本研究阐明了轻度和重度缺镁条件下茶树品质成分的代谢变化，有利于提高茶叶品质。