Immunocytochemical detection of lignin-related epitopes in cell walls in bryophytes and the charalean alga Nitella

Lignins are complex phenolic heteropolymers present in xylem and sclerenchyma cell walls in tracheophytes. The occurrence of lignin-like polymers in bryophytes is controversial. In this study two polyclonal antibodies against homoguaiacyl (G) and guaiacyl/syringyl (GS) synthetic lignin-like polymers that selectively labelled lignified cell walls in tracheophytes also bound to cell walls in bryophytes, the GS antibody usually giving a stronger labelling than the G antibody. In contrast to tracheophytes, the antibody binding in liverworts and mosses was not tissue-specific. In the hornworts Megaceros flagellaris and M. fuegiensis the pseudoelaters and spores were labelled more intensely than the other cell types with the GS antibody. The cell walls in Nitella were labelled with both antibodies but no binding was observed in Coleochaete. The results suggest that the ability to incorporate G or GS moieties in cell walls is a plesiomorphy (primitive character) of the land plant clade.