Extensibility of cell wall

Transfer cells Specialized parenchyma cells, plasmalemma greatly extended, irregular extensions of cell wall into protoplasm Transfer dissolved substances between adjacent cells, presence is correlated with internal solute flux... 

Varner, 1988). Extensin is secreted as single soluble monomeric hydroxyproline forms that are slowly insolubilized in the cell wall, probably via the oxidative formation of isodityrosine cross-links (Cooper and Varner, 1983 Fry, 1986a). Wall-catalyzed cross-linking of soluble extensin is inhibited by ascorbate, indicating that this reaction is dependent on an oxidative mechanism (Cooper and Varner, 1984). Thus, it is probable that a cell wall-bound peroxidase-ascorbate oxidase system controls the redox state at the wall, and hence the extensibility of cell wall, by controlling the cross-linking of wall glycoproteins. 

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