Background: Antarctic bryophytes (mosses and liverworts) are resilient to physiologically extreme environmental
conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone. Many
Antarctic bryophytes synthesise UV-B-absorbing compounds (UVAC) that are localised in their cells and cell walls, a
location that is rarely investigated for UVAC in plants. This study compares the concentrations and localisation of intracellular
and cell wall UVAC in Antarctic Ceratodon purpureus, Bryum pseudotriquetrum and Schistidium antarctici from
the Windmill Islands, East Antarctica.
Results: Multiple stresses, including desiccation and naturally high UV and visible light, seemed to enhance the
incorporation of total UVAC including red pigments in the cell walls of all three Antarctic species analysed. The red
growth form of C. purpureus had significantly higher levels of cell wall bound and lower intracellular UVAC concentrations
than its nearby green form. Microscopic and spectroscopic analyses showed that the red colouration in this
species was associated with the cell wall and that these red cell walls contained less pectin and phenolic esters than
the green form. All three moss species showed a natural increase in cell wall UVAC content during the growing season
and a decline in these compounds in new tissue grown under less stressful conditions in the laboratory.
Conclusions: UVAC and red pigments are tightly bound to the cell wall and likely have a long-term protective role
in Antarctic bryophytes. Although the identity of these red pigments remains unknown, our study demonstrates the
importance of investigating cell wall UVAC in plants and contributes to our current understanding of UV-protective
strategies employed by particular Antarctic bryophytes. Studies such as these provide clues to how these plants survive
in such extreme habitats and are helpful in predicting future survival of the species studied.