Between the Constituent Polymers in Primary Cell-Walls of Monocots

Interconnections Between the Constituent Polymers in Primary Cell-Walls of Monocots 

There have been few studies of polymer interconnections within the primary wall of monocots. An arabinoxylan from the primary wall of cultured, barley-aleurone cells,61 and a glucuronoarabinoxylan from maize-coleoptile primary-wall,200 have been shown to bind reversibly to cellulose in vitro, Because xylans are, quantitatively, the major component of monocot primary cell-walls, this interconnection is an important finding it is very likely to occur through multiple hydrogen-bonds, analogous to the interconnection between xyloglucan and cellulose in dicot cell-walls.56,57,59 It is also possible that heteroxylans participate in binding other cell-wall polymers to cellulose. 

In contrast to these findings, a glucuronoarabinoxylan isolated from oat coleoptiles did not bind to cellulose in vitro under reaction conditions that allowed other heteroxylans to bind.53 This oat heteroxylan had, however, a high percentage of arabinosyl side chains that would be likely to hinder binding sterically. A similar inability to bind to cellulose is exhibited by an arabinose-rich arabinoxylan isolated from cultured, barley-aleurone cell-walls.61 

As with dicots, it is probable that monocot xylans bind to each other, as 

Some monocot, primary cell-wall polysaccharides may be cross-linked by esters of ferulic acid (4-hydroxy-3-methoxycinnamic acid). There is evidence for the existence of such cross-links in monocot tissues containing secondary walls, including Italia ryegrass stem276 and wheat endosperm.277 Ferulic acid is also present in barley cell-wall,278 and it has been reported that treatment with base releases ferulic acid from the cell walls of several Graminae,276 supporting the idea that ferulic acid is bound to the wall as an ester. However, ferulic acid has not, so far, been reported to be present specifically in primary cell-walls in either monocots or dicots. 

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