Cell compartmentation of ultraviolet-absorbing compounds: an underexplored tool related to bryophyte ecology, phylogeny and evolution

1. Excessive exposure to ultraviolet (UV) radiation can be harmful to photosynthetic organisms, that most frequently respond with the accumulation of protective UV-absorbing compounds (UVACs). UVACs location in different cell compartments can influence their preferential protective role as antioxidants and/or UV screens. However, the phylogenetic, ecological and evolutionary implications of UVACs compartmentation has been little studied, particularly in bryophytes. 2. We analysed UVACs in the methanol-soluble and -insoluble fractions (SUVACs and IUVACs, respectively) in extracts of 87 bryophytes belonging to their three evolutionary lineages: 22 liverworts, 64 mosses and 1 hornwort. Assuming that the cell wall-bound IUVACs are more effective UV screens than the mainly vacuolar SUVACs, thus conferring a higher UV tolerance, we evaluated whether UVACs levels and compartmentation were related to: 1) the bryophyte phylogeny down to the Order level; and 2) the bryophyte ecological attributes...