圆叶玉兰叶片非结构性碳水化合物与氮、磷含量对海拔的响应

非结构性碳水化合物(non-structural carbohydrates, NSC)、氮(N)和磷(P)是植物生长的重要能源物质和影响植物分布的限制生长因子,圆叶玉兰(Magnolia sinensis)是四川省特有的珍稀濒危极小种群野生植物,研究其NSC、N和P可以反映它的营养供应水平及对环境的适应策略。选取芦山6个海拔梯度(1840,1960,2070,2170,2270,2390 m)的圆叶玉兰为对象,研究不同海拔下圆叶玉兰叶片中NSC与N、P及其化学计量间的关系。结果表明,圆叶玉兰叶片可溶性糖含量在2390 m处显著高于1840 m处, NSC含量在不同海拔差异极显著,随海拔增加呈"低-高-低"的单峰变化,2170 m处叶片NSC含量最高,碳水化合物供应充足;可溶性糖/淀粉的比值随海拔升高呈增大趋势,N含量和N/P比都随海拔上升而下降,且N/P比在各海拔上均小于14,NSC/N比在2390 m处显著高于1840 m处。总之,圆叶玉兰叶片的可溶性糖和NSC含量显著不受海拔的影响,较高的可溶性糖含量有利于抵御低温环境,其生长主要受氮元素限制而不受碳限制,反映了濒危植物圆叶玉兰在其有限的分布范围内NSC及N、P的保护策略,为圆叶玉兰的碳代谢和生长适应对策提供数据基础。

Responses to non-structural carbohydrates and nitrogen and phosphorus content in the leaves of Magnolia sinensis along different altitude gradients

Non-structural carbohydrates (NSC), nitrogen (N), and phosphorus (P) are important energy sources for plant growth, and their deficiencies affect plant growth factors. Magnolia sinensis is a rare and endangered species of wild plant in Sichuan province, and studies of its NSC, N, and P can reflect its nutritional supply level and adaptation strategies to the environment. The present study was conducted to evaluate M. sinensis at six altitudes (1840, 1960, 2070, 2170, 2270, 2390 m) in Lushan, and the NSC, N, and P content and their stoichiometry in the leaves at different altitudes were analyzed. The results showed that the soluble sugar content of M. sinensis in 2390 m leaves was significantly higher than that in 1840 m leaves. The NSC content at different altitudes was extremely significant, showing a unimodal change of "low-high-low" with increasing altitude. The NSC content of 2170 m leaves was the highest, and the carbohydrate supply was sufficient, ratio of soluble sugar/starch increased with altitude, N content and N/P ratio decreased with altitude, and N/P ratio was less than 14. The NSC/N ratio at 2390 m was significantly higher than that at 1840 m. The results showed that the soluble sugar and NSC content in the leaves of M. sinensis were not affected by the altitude, a higher soluble sugar content was beneficial for resisting the low-temperature environment, and growth was mainly limited by nitrogen but not by carbon. The protective strategies of NSC, N, and P in the limited distribution range of the endangered plant M. sinensis were determined, providing information on carbon metabolism and adaptation strategies used by this plant.