School of Earth System Science, Tianjin University, Tianjin 300072, China.
Ying Yong Sheng Tai Xue Bao. 2024 Jul 18;35(7):1859-1865. doi: 10.13287/j.1001-9332.202407.016.
Atmospheric nitrogen (N) deposition could affect the structure and function of terrestrial plants. Non-N-fixing lichens are used to monitor atmospheric N deposition because they rely on the deposited inorganic N (., ammonium and nitrate) as N sources. However, the uptake capacities of lichen on ammonium and nitrate remain unclear, which hinders the application of lichen N content to accurate bioindication of atmospheric N deposition levels. We investigated ammonium and nitrate uptake capacities of , which was treated with ammonium alone, nitrate alone, and ammonium and nitrate mixture solutions with different mixing ratios under light and dark conditions. The results showed that N uptake rates increased with ammonium and nitrate concentrations in solutions and generally followed the Michaelis-Menten saturation kinetics. Ammonium uptake of showed higher values of affinity, and was more efficient than the nitrate uptake. Both rates and amounts of nitrate uptake decreased with increasing ratios of ammonium to nitrate in solutions, while ammonium uptake showed no substantial variations, indicating an inhibition of ammonium on nitrate uptake capability. The darkness significantly decreased the maximum uptake rate and efficiency of nitrate, but had much weaker effects on lichen ammonium uptake. These findings highlight the preference of lichen on ammonium as a key N uptake strategy. It is thus necessary to consider the main types of atmospheric inorganic N deposition when using lichens to monitor atmospheric N pollution levels and evaluate N deposition based on lichen ecophysiology.
大气氮（N）沉降会影响陆地植物的结构和功能。非固氮地衣被用于监测大气 N 沉降，因为它们依赖于沉降的无机 N（铵和硝酸盐）作为 N 源。然而，地衣对铵和硝酸盐的吸收能力仍不清楚，这阻碍了地衣 N 含量在大气 N 沉降水平的准确生物指示中的应用。我们研究了地衣在光照和黑暗条件下，单独用铵处理、单独用硝处理以及用不同混合比的铵和硝混合溶液处理时，对铵和硝的吸收能力。结果表明，N 吸收速率随溶液中铵和硝浓度的增加而增加，通常遵循米氏-门捷列夫饱和动力学。地衣对铵的吸收具有更高的亲和力值，比硝酸盐的吸收更有效。随着溶液中铵与硝比例的增加，硝酸盐的吸收速率和量都减少，而铵的吸收则没有明显变化，表明铵对地衣硝酸盐吸收能力的抑制作用。黑暗显著降低了硝酸盐的最大吸收速率和效率，但对地衣铵的吸收影响较弱。这些发现突出了地衣对铵的偏好作为一种关键的 N 吸收策略。因此，在用地衣监测大气 N 污染水平和根据地衣生理生态评估 N 沉降时，有必要考虑大气无机 N 沉降的主要类型。
