Primary cell walls (PCWs) of major vascular plant taxa were analysed as a contribution towards understanding wall evolution.
Alcohol-insoluble residues from immature shoots were acid- or enzyme-hydrolysed and the products analysed chromatographically and electrophoretically.
There were phylogenetic differences in abundance of mannose, galacturonate and glucuronate residues, mixed-linkage glucan (MLG) and tannins. Eusporangiate pteridophytes (lycopodiophytes, a psilotophyte, an equisetophyte and a eusporangiate fern) were richer in mannose than leptosporangiate ferns, gymnosperms and angiosperms. Galacturonate was always the most abundant uronate; glucuronate was not abundant in PCWs of vascular plants except angiosperms (especially monocots and some magnoliids). MLG was detected in the Poaceae and Flagellariaceae, but no other vascular plants. Proanthocyanidins were associated with PCWs from leptosporangiate ferns, gymnosperms and some angiosperms, but not eusporangiate pteridophytes. Xyloglucan was present in all vascular plants tested.
The results imply that major evolutionary changes in the PCW occurred not only during the charophyte-bryophyte and bryophyte-lycopodiophyte transitions but also after plants attained the vascular condition and upright growth habit, particularly during the eusporangiate-leptosporangiate transition.