Differences in Ploidy and Degree of Intercellular Contact in Differentiating and Non-Differentiating Sycamore Calluses

Use of antisera to localize callose, xylan and arabinogalactan in the cell-plate, primary and secondary walls of plant cells

Antibodies to cellobiose, L-arabinopyranose, L-arabinofuranose, D-galactose, oligosaccharides containing β1→4 xylose, oligosaccharides containing β1→4 glucose, and oligosaccharides containing β1→3 glucose have been raised in rabbits. The antisera have been characterized to show the specificity of binding to particular polysaccharides. They have been used for immunocytology using the electron microscope to locate the polymers in dividing and differentiating cells of bean (Phaseolus vulgaris L.) root, bean callus tissue and cells of Zinnia elegans L. in vitro. Arabinogalactans have been shown to be present in the cell-plate and primary walls but not in secondary thickening. Xylan as distinct from xyloglucan was found in the primary walls but not in the cell-plate. It was present in large amounts in the secondary thickening. Callose was found in the cell plate and also in the young growing wall. In the wall it was specifically located at the plasmodesmata. The use of the antibody against L-arabinofuranose enabled a specific organelle to be detected which was membranous and which occurred within the cytoplasm and also within the vacuole of the cells. Membranes carrying polymers containing L-arabinofuranose were also found in layers just under the plasmamembrane.

A deficiency of hypoxanthine phosphoribosyltransferase in a sycamore callus resistant to azaguanine

Sycamore (Acer pseudoplatanus L.) calluses resistant to azaguanine were isolated after mutagenesis with nitrosoguanidine. One callus SNC61 was highly variable in its growth on 10 μg/ml azaguanine and it was concluded that its resistance was not due to a stable alteration in the callus. Another callus SNE31 was isolated after 4.5 months culture in 0.5 or 1 μg/ml azaguanine which had a 10-fold increase in resistance to azaguanine. This was shown to be accompanied by a reduction to 50% of the normal level of hypoxanthine phosphoribosyltransferase (E.C.2.4.2.8).