文冠果叶片养分元素含量的动态变化及再吸收特性

以文冠果叶片为试材，运用原子吸收光谱法分析了叶片养分元素含量的季节动态变化和再吸收效率。结果表明：N、P、K均呈下降趋势，是“稀释效应”和养分再吸收导致；Mg呈“单峰”曲线走势，与Mg的生理功能有关；Fe、Mn呈“V”字型走势，Cu呈“W”型，Zn呈“N”型，与树体吸收特性和不同的物候期有关。总体来看，养分元素含量顺序是：N>P>K>Mg>Fe>Zn>Mn>Cu，且不同时期又有所不同。大量元素之间存在显著的相关关系；微量元素间相关关系不显著（Fe、Zn除外），Fe与N显著负相关，与拮抗作用有关。C/N呈升高趋势，差异显著；N/P呈降低趋势，差别不大。养分再吸收效率由大到小的顺序是：Mg>N>K>P，差异显著。微量元素由于移动性较差，不能被再吸收。N、P、K、Mg养分再吸收效率反映了文冠果较高的养分保存能力和养分利用效率。

Dynamic Variation and Resorption of Nutrient Elements in the Leaves of Xanthoceras sorbifolia Bunge

The contents and resorption efficiencies of N, P, K, Mg, Cu, Zn, Fe and Mn in the leaves of Xanthoceras sorbifolia Bunge were measured by atomic absorption spectroscopy. N, P, and K declined throughout the growing season. This was probably a consequence of “dilution effect” and resorption of nutrients. Mg presented a single peak curve, which was probably resulted from physiological functions. Fe and Mn presented “V”-shaped trends, Cu “W” and Zn “N”. These phenomena may be related to nutrient absorption characteristics of the trees and phenological periods. Overall, the order of contents was N>P>K>Mg>Fe>Zn>Mn>Cu. But the order differed with time. Positive correlations occurred significantly between macroelements. By contrast, there was no significant correlation between microelements except Fe and Zn. A negative correlation occurred significantly between Fe and N. It was probably caused by antagonistic actions. The C/N ratio increased significantly. However, the N/P ratio decreased insignificantly. Nutrient resorption efficiency was in the order of Mg>N>K>P, with significant difference. Microelements can not be absorbed because of their poor mobility. The nutrient resorption efficiency of N, P, K, Mg reflects the higher ability of nutrient conservation and use efficiency.