Evolution has a major influence on the plant cell wall and variation in primary cell wall (PCW) composition is known to exist between different angiosperm taxa. The PCWs of lower land plants have not been well studied. It is of interest to see what changes have taken place in PCW composition during plant evolution. One of the main qualitative variables within angiosperms is the presence of mixed-linkage b-(1(r)3),(1(r)4)-glucan (MLG) in gramineous monocots and apparent absence from non-gramineous monocots and dicots. Anomolously, the presence of MLG had been reported in the dicot <i>Phaseolus aureus. </i>In the present work, MLG was not detected (< 0.02% w/w of the cell wall) in <i>P. aureus </i>hypocotyls or in PCWs of all non-gramineous land plants tested (dicots, monocots, pteridophytes and bryophytes). One exception was <i>Flagellaria guineensis,</i> a close relative of the gramineous monocots, which on licheninase digestion produced the characteristic tri- and tetrasaccharide of MLG. MLG is therefore restricted to the Poaceae and some closely related members of the Poales. Xyloglucan was found in all land plants tested including bryophytes. Methylation analysis had indicated some of the glycosyl linkages typically found in xyloglucan are present in a cell wall polymer from the charophyte <i>Nitella. </i>However, Driselase-digestible xyloglucan was not detected (< 0.01% w/w of the cell wall) in <i>Chara</i>, a charophyte, thought to be closely related to land plants. In addition, PCWs of <i>Chara</i>, two other charophytes and <i>Ulva lactuca</i> were not digested to xyloglucan-derived oligosaccharides by cellulase or xyloglucan-specific endoglucanase. Land plants are thought to have organised from a single species of charophyte: it is therefore likely the putative ancestor, unlike other charophytes, had xyloglucan in its cell walls.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:660687 |
| Date | January 2001 |
| Creators | Popper, Zoe Adelaide |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12794 |
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