Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal.
Environ Sci Pollut Res Int. 2017 Dec;24(36):28065-28071. doi: 10.1007/s11356-017-0378-3. Epub 2017 Oct 9.
The mechanisms of nitrogen (N) tolerance in lichens are not yet fully understood. Here, we investigated how the increase of chitin content is related with N excess at inter- and intra-specific levels, by using species with differing ecological N tolerances (the tolerant Xanthoria parietina and Parmotrema hypoleucinum and the sensitive Evernia prunastri and Usnea sp.) and thalli of X. parietina and P. hypoleucinum from sites with different availabilities of N of agricultural origin (livestock), as confirmed by lichen N content and δN. Nitrogen, chitin (N-containing compound), and ergosterol contents were measured in lichen thalli. Nitrogen and chitin contents were higher in tolerant species than those in sensitive ones (inter-specific level) and in thalli collected from the N-polluted site than in thalli from the clean site (intra-specific level). We suggest that chitin contributes to N stress tolerance in lichens, and that excess N can be partially stored as chitin (non-toxic form) in the cell walls of tolerant species.
地衣对氮（N）的耐受机制尚未完全了解。在这里，我们通过使用具有不同生态氮耐受性的物种（耐氮的 Xanthoria parietina 和 Parmotrema hypoleucinum 以及敏感的 Evernia prunastri 和 Usnea sp.）以及来自具有不同农业来源氮可用性（牲畜）的地点的 X. parietina 和 P. hypoleucinum 的叶状体，研究了叶状体中几丁质含量与 N 过量之间的关系，这一点通过地衣 N 含量和 δN 得到了证实。我们在地衣叶状体中测量了氮、几丁质（含氮化合物）和麦角固醇含量。在耐氮物种中，氮和几丁质含量高于敏感物种（种间水平），并且在从受 N 污染的地点收集的叶状体中，氮和几丁质含量高于在从清洁地点收集的叶状体中（种内水平）。我们认为，几丁质有助于地衣耐受氮胁迫，并且过量的 N 可以部分作为几丁质（无毒形式）储存在耐氮物种的细胞壁中。
