Direct visualization of cross-links in the primary plant cell wall

摘要: We have investigated the structure of onion primary cell wall at high resolution, using shadowed replicas rapidly frozen deep-etched specimens. We sequentially extracted polymers from and visualized both these remaining structures each extraction step. By viewing in as near their native state possible, an accurate three-dimensional picture construction has been assembled, facilitated by stereo pairs micrographs. Our observations show that physical links between cellulose microfibrils we observe intact are generally shorter (20–40 nm) than isolated molecules extract (30->700nm), suggesting lateral interactions must occur linking muro . These cross-links hemicellulosic believe them to be xyloglucans: removal allows increased association microfibrils. Na2CO3-extractable pectic fractions form a separate coextensive network, which does not affect basic cellulose/ hemicellulose architecture. Preliminary evidence for lamellate model obtained. In addition, propose positive role maintaining ordered spacing micronbrils, perhaps regulating porosity strength. The parameters derive impose constraints on possible models.