Plant Protoplasts Immobilized in Calcium Alginate: A Simple Method of Preparing Fragile Cells for Transmission Electron Microscopy

A simple method for electron microscopic preparation of plant protoplasts is described. The main problems in preparing these fragile protoplasts for electron microscopy have been cell collapse due to steep gradients between protoplasts and fixatives and unacceptable loss of material during the many steps of the procedure. These problems may be solved by immobilization of the protoplasts in calcium alginate beads. The free diffusion properties of this gel prevent steep gradients. The beads also simplify handling and prevent loss of material. Protoplasts isolated from hypocotyls of rape, Brassica napus (var. Niklas), have been used as a model system. Transmission electron microscopy of the immobilized protoplasts osmotically stabilized with glucose demonstrated adequate structural and ultrastructural preservation.     

Aerobic microbial degradation of alginate in Laminaria hyperborea stipes containing different levels of polyphenols

The polyphenols present in brown seaweed tissue may seriously affect aerobic microbial degradation, particularly the alginate present. Laminaria hyperborea stipes, harvested at 59 °N off the Norwegian coast in autumn, were degraded at different levels of polyphenols in aerated batch reactors at 35 °C and pH 7. This was achieved by manipulating the relative amounts of peripheral tissue, by removing or adding the mechanically peeled outer phenolic layer, using standardized inocula already adapted to L. hyperborea degradation. The degradation of organic matter was clearly depressed by increasing the amount of peripheral tissue. Alginate lyase activity was also negatively correlated to the amount of peripheral tissue loaded, presumably due to the release of reactive polyphenols. The total digestion rates of alginate were reduced by more than a factor of two at enhanced amounts of peripheral tissue. The guluronic content of extracted Na-alginate increased during the degradation, despite the presence of significant amounts of guluronate specific alginate lyase activity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Biodegradation of amine waste generated from post-combustion CO2 capture in a moving bed biofilm treatment system

Nitrogen and organic matter removal from reclaimer waste of a monoethanolamine (MEA) based CO₂-capture plant was demonstrated in a pre-denitrification biofilm system. The reclaimer waste was generated from a 30 % (w/w) MEA solvent used for capturing CO₂ from flue gas from a coal-fired power plant. MEA, N-(2-hydroxylethyl)glycine (HEGly) and 2-hydroxyethylformamide (HEF) were the major contaminants treated. Hydrolysis of MEA to ammonia and further oxidation of organic intermediates readily occurred in the pre-denitrification system with a hydraulic retention time of 7 h. The biofilm system achieved 98 ± 1 % removal of MEA and 72 ± 16 % removal of total nitrogen. This is the first demonstration of efficient biodegradation of real amine waste from a post-combustion CO₂ capture facility by pre-denitrification without external electron donor.     

Microcomputer-assisted systems for recording and control of growing phytoplankton cultures

This report describes a basic unit for microcomputer-assistedrecording of the turbidity of phytoplankton cultures. The unitis applied in several experimental systems for single and multiplebatch and dilution cultures in combination with different typesof control functions. These applications include: (i) singlebatch cultures with double-beam recording, temperature compensation,manual or automatic dilution and sampling; (ii) a multiturbidometerdesigned to record the growth of 16 batch cultures simultaneously;and (iii) a triple cage-culture turbidostat system. Selectedexamples of application with Skeletonema costatum have alsobeen included to illustrate some of the possibilities of suchmicrocomputer-assisted systems. These examples include studiesof ultradian growth rhythms, toxicity testing and light–shadeadaptation.     

The controls of late dicot embryogenesis and early germination

During seed formation, the embryo appears to be germinable as soon as cell division is completed; however, it continues development on the plant. This review describes the stages of development after cell division and provides a summary of important observations and recent use of molecular markers as they apply to the regulation of dicot seed formation. Genetic evidence suggests that abscisic acid may help initiate late embryogenesis, although no evidence firmly establishes that abscisic acid controls any other aspect of late dicot development. Previous studies utilizing cultured embryos have implicated abscisic acid and water potential as endogenous promoters of late embryogenesis and inhibitors of germination. However, these embryo culture experiments have been misinterpreted. The experiments show that both immature and mature embryos respond to environmental water stress by expressing a developmental program that is normally induced in late embryogenesis by abscission of the vascular connection. This postabscission program probably prepares the embryo for its forthcoming desiccation during normal development and is predicted to be important in protecting the embryo from water stress during germination.