Preliminary attempts at ultrastructural polysaccharide localization in root tip cells

A basic method and many variations are described which initially appear to give good ultrastructural localization of polysaccharide material and also sulfhydryl groups in sections of plant tissues. Using permanganate fixation, alkaline silver hexamine solutions very strongly stained cell walls and starch grains (if they survived the treatment) in thin sections; in root cap and epidermal cells, Golgi bodies and associated vesicles also strongly reacted. The reaction was markedly reduced if sections were pretreated with aldehyde-complexing reagents (dimedone, etc.) and reintroduced after such blocking reactions by further periodate oxidation. Apart from a variable unspecific argentophilic reaction of manganese in the sections (which does not appear if the manganese is leeched out), other components of the cells showed very little staining in permanganate-fixed cells. Differences were noted between the reactivity of various polysaccharides. A strong generalized staining reaction was observed over sections of glutaraldehyde-fixed tissues, and this could be almost entirely blocked by pretreatment of the sections with iodoacetate; such treatment also indicated that there were comparatively few aldehyde groups present, either native and/or introduced by the fixative. Periodate oxidation then introduced staining groups in some Golgi bodies and cell walls, particularly in epidermal cells.

Somatic association in Triticum aestivum

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The effect of chromosomes 5B, 5D, and 5A on chromosomal pairing in triticum aestivum

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Geotropic response of wheat coleoptiles in absence of amyloplast starch

Young coleoptiles of wheat (Triticum durum var. Henry), depleted of amyloplast starch by incubation at 30 degrees C with gibberellin plus kinetin, retained their geotropic responsiveness. Depleted coleoptiles curved upward more slowly than controls, but this was commensurate with their slower growth. The ratio of curvature to growth was about 50 degrees per mm of elongation in both cases. Newly excised coleoptiles, though containing much more starch than incubated controls, curved only about 25 degrees per mm. The tissue treated in gibberellin plus kinetin appeared to contain no starch when examined (a) freshly squashed, (b) as fixed material sectioned thin and stained by the PAS procedure, and (c) as electron micrographs. Shrunken, starch-free amyloplasts could be identified in certain regions, but these did not show evidence of asymmetric distribution under the influence of gravity. The possibilities that other organelles function as statoliths are considered, and it is concluded not only that georeception is independent of starch grains, but further that it may not be due to statoliths at all in an ordinary sense.

A function of the Golgi apparatus in polysaccharide synthesis and transport in the root-cap cells of wheat

1. A radioautographic study of the cells of the root tips of wheat incubated with d-[1- or 6-(3)H]glucose has shown that labelled material is formed in the golgi apparatus of the root-cap cells. This material passed to the vesicles associated with the golgi bodies and then moved through the cytoplasm across the plasmalemma and was incorporated into the cell wall and slime layer of the tissue. 2. Analysis of the labelled material extracted from the root tips showed that the bulk of the radioactive material was polysaccharide; there were relatively small amounts of labelled lipids and protein in the tissue. 3. Starch was formed from the exogenous labelled glucose and it was located in the plastids of the cell. The synthesis of starch depended on the metabolic activity of the cells, which varied with the position of the cell in the various tissues of the root tip and with the amount of the exogenous glucose. 4. Isolation of the radioactive polysaccharides from the root tip incubated in the radioactive glucose has shown that the glucose was very rapidly incorporated into the galactosyl residues of the polymers. 5. Analysis of the radioactive polysaccharides has indicated that the material transported in the golgi vesicles is probably pectic substance. 6. A scheme for the synthesis of the storage and wall polysaccharides by separate routes and their location within the cell has been put forward.

Nuclear DNA and cytoplasmic DNA from tissues of higher plants

Young wheat roots were labeled with (32)P-inorganic phosphate. Following the labeling period, roots were homogenized in a sucrose medium and fractionated into nuclei, cytoplasmic particles (including proplastids and mitochondria), and a soluble fraction containing most of the microsomes. DNA prepared from the particles had a higher buoyant density than that from the nuclei and showed a marked loss in total label if the roots were exposed to non-radioactive medium for 48 hours prior to fractionation of the cells.

Intracellular components associated with protein synthesis in developing wheat endosperm

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