Munzi, S., Cruz, C., Maia, R., Máguas, C., Prestello-Ramos, M.M. & Branquinho, C. (2017) Intra- and inter-specific variations in chitin in lichens along a N-deposition gradient.Environmental Science & Pollution Research, 24(36), 28065-28071. DOI:10.1007/s11356-017-0378-3 (IF2017 2.800; Q1 Environmental Sciences)
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 δ15N. 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.