A glucomannan from Arum korolkovii
SummaryA glucomannan has been isolated from the tubers ofArum korolkovii Regel. It has been shown that the polysaccharide contains O-acetyl groups and consists mainly of (1 → 4)-β-linked aldohexopyranose units of glucose and mannose in a ratio of 1:1.6. The nonreducing ends of the glucomannan are glucose residues, and branching is localized at C2 and C3 of mannose.
Plant Mucilages. I. Isolation and Property of a Mucous Polysaccharide, “Plantasan, ” from Plantago major L. var. asiatica Seeds
An acidic polysaccharide has been isolated from the seed of Plantago major L. var. asiatica DECAISNE. The polysaccharide, named plantasan, was homogenous on gel chromatography and glass-fiber paper electrophoresis, and it was the representative mucilage of the seed. The component carbohydrates of it were D-xylose, L-arabinose, D-galacturonic acid, L-rhamnose and D-galactose, and the molar ratio of them was 15 : 3 : 4 : 2 : O. 4.
The role of early lithification in development of chalky porosity in calcitic micrites: Upper Cretaceous chalks, Egypt
Abstract Petrological and geochemical examination of Upper Cretaceous chalks from the Abu Roash area and Bahariya Oasis (Egypt) provide insights into factors which control porosity development in fine-grained calcitic carbonates. Petrological studies indicate that primary skeletal fabrics of coccoliths and foraminifera in micrites of Abu Roash are well preserved. In contrast, primary skeletal fabrics of the Bahariya Oasis chalks are pervasively altered. Geochemical analysis of these chalks reveals a striking contrast in composition. The high porosity chalks at Bahariya Oasis have depleted isotopic values ( δ 13 C = −5.0‰, δ 18 O = −8.9‰ PDB ) and low concentrations of trace elements (Sr and Na). In contrast, the low porosity chalks at Abu Roash are less depleted in terms of their isotopic values ( δ 13 C = 1.0‰, δ 18 O = −4.0‰ ) and possess elevated concentrations of Sr, Na, Fe and Zn. Importantly, fracture and collapse veins, present only at Abu Roash, are filled with calcite whose δ18O value is coincident with that of altered micrites at Bahariya Oasis. The lithic fragments cemented by this calcite, however, retain compositions identical to other lithified limestones at Abu Roash. Differences in fabric and chemistry of the pelagic marine micrites observed between Abu Roash and Bahariya Oasis reflect the degree of early lithification and compaction prior to exposure and meteoric diagenetic alteration associated with regional Late Cretaceous/pre-Eocene subaerial unconformity.