Unravelling the evolutionary significance of non-lignin cell wall-bound phenolics: a multi-experimental analysis of fern sclerenchyma tissues

When plants colonized land they needed adaptations to survive this new environment. Phenolic
compounds must have been of great importance to early land plants, given their functional roles as
cell wall strengthening components, light screens against intensive irradiation and phytophagy
deterrents. Lignin, one of the most studied phenolic compounds, is generally thought to have played
a pivotal role in strengthening mechanical and vascular tissues. However, recently we discovered
that ferns may develop two chemically distinct types of sclerenchyma with similar hardness: a
lignified and non-lignified type. Further analysis indicated that the latter type is impregnated with
(currently unidentified) phenolic pigments. The first goal of this project is to characterise the
chemical nature of these pigments using pyrolysis-based and thermally-assisted chemical analyses.
Given the different functional roles of phenolics, the second goal is to gain insights into why ferns
may have employed different chemical strategies – based on highly diverse phenolic compositions –
to strengthen sclerenchyma walls. Therefore, we adopt a multi-experimental approach to assess the
susceptibility of sclerenchyma tissues to fungal decay as well as the effect of mechanical
perturbation and physical wounding on the phenolic composition of sclerenchyma. Integration of
the results will provide new insights into the functional and evolutionary significance of wall-bound
phenolic compounds in land plants.