The white-rot fungus Resinicium bicolor was cultured on wood blocks in a modified soil block assay and was observed by environmental scanning electron microscopy and scanning electron microscopy. Resinicium bicolor was found to translocate calcium in mycelial cords in quantities greater than that found in the wood blocks and accumulated this calcium in the form of calcium oxalate. Calcium oxalate crystal clusters of mycelial cords were 3 × larger and far more numerous than the crystal clusters produced by the same fungus within the wood. Environmental scanning electron microscopy technology allowed for the examination of the hyphal sheath in a hydrated state. The hydrated hyphal sheath was found to be much thicker than the desiccated sheath observed after standard scanning electron microscope preparations. Calcium oxalate crystals were found to be embedded in the thick hyphal sheath, suggesting that previous observations of within-wall calcium oxalate precipitation may perhaps be better interpreted as artifacts generated during sample preparation. Key words: calcium oxalate, hyphal sheath, environmental scanning electron microscopy.
This review focuses on the important physiological messenger, nitric oxide (NO), and its role in N-methyl-D-aspartate (NMDA) excitotoxicity. NO has been shown to be a key mediator of voltage-gated Ca +2 transmembrane proteins. It remains unclear whether NO is implicated during hypoxia, or ischemic/reperfusion injuries as a neuroprotective or neurodegenerative factor. Excitotoxicity results from the excessive stimulation of excitatory glutamate receptors within the CNS. This review maintains that the feed-forward pathway precipitated by oxidative stress is the discriminating factor in the neuroprotective or neurodegenerative actions of NO.
The white-rot wood decay fungus Resinicium bicolor (Abertini & Schwein.: Fr.) Parmasto was studied for its ability to solubilize and translocate ions from the naturally occurring mineral strontianite. Resinicium bicolor colonized a soil mixture culture medium containing strontianite sand, solubilized strontium ions from this mineral phase, translocated the ions vertically, and reprecipitated the strontium into strontium-containing calcium oxalate crystals. Storage of the Sr in crystals was highest in mycelial cords and was dynamic in character. These results suggest that non-mycorrhizal saprotrophic fungi should be evaluated for their potential participation in forest nutrient cycling via biologically weathering parent material and translocating the mobilized mineral nutrients vertically within soils.Résumé : Les auteurs ont étudié le champignon de carie blanche Resinicium bicolor (Abertini & Schwein.: Fr.) Parmasto, quant à sa capacité à solubiliser et à transloquer les ions à partir de la strontianite, un minérai naturel. Le R. bicolor colonise un milieu de culture à base d'un mélange de sol contenant de la strontianite, solubilise les ions strontium à partir de cette phase minérale, transloque les ions verticalement et reprécipite le strontium dans des cristaux d'oxalate de calcium contenant du strontium. L'accumulation du Sr dans les cristaux est plus importante dans les cordons mycéliens et est de caractère dynamique. Ces résultats suggèrent que des champignons non-mycorhiziens saprophytes devraient faire l'objet d'une évaluation quant à leur capacité à participer au cyclage des éléments en milieu forestier, via l'altération biologique de la roche mère et la translocation verticale dans le sol des nutriments ainsi mobilisés.
Environmental scanning electron microscopic observations of Postia placenta grown on a defined medium and on red spruce wood allowed for the examination of the hydrated sheath of P. placenta. In the wood environment, mature hyphae that were not adhering to the substrate were observed to have a mycofibrillar morphology whereas hyphal tips and branch points had a smooth sheath morphology. A mycofibrillar adhesive matrix was observed on the hyphae growing on glass slides in the defined medium. These morphologies for hyphal sheaths in P. placenta are similar to those previously described by investigators from other laboratories who have used traditional electron microscopic preparative protocols that include dehydration steps. The potential future usefulness of environmental scanning electron microscopic technology in the study of the fine details of extracellular matrices is briefly discussed.
The study of the underground parts of plants is often difficult, and as a result roots are often treated as homogeneous physiological entities with respect to root respiration. In this study we demonstrate a partitioning of respiration within root tissues using nitro blue tetrazolium staining and an incident light optical system that permits detailed observations of intact roots. The assay is rapid and easy to perform, and reveals that respiratory activity in roots is not uniform in space and time. The results show that root hairs in particular may be regions of enhanced respiratory activity in some species or in certain developmental or physiological states. This fact has important implications for the role of root hairs in the overall respiratory budget of roots and the energetics of nutrient assimilation. The results suggest that root respiration studies should consider differential respiratory activities of root cell types within roots.
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