Chemical and Ultrastructural Features of the Lichen-volcanic/Sedimentary Rock Interface in a Semiarid Region (Almería, Spain)

2002 ◽  
Vol 34 (2) ◽  
pp. 155-167 ◽  
Author(s):  
Virginia Souza-Egipsy ◽  
Jacek Wierzchos ◽  
Jose Vicente García-Ramos ◽  
Carmen Ascaso
Keyword(s):  
Calcium Oxalate ◽  
Cell Walls ◽  
Close Contact ◽  
Lichen Species ◽  
Semiarid Region ◽  
Rock Surface ◽  
Calcium Oxalate Crystals ◽  
Volcanic Material ◽  
Oxalate Crystals ◽  
Oxalate Precipitation

AbstractThe chemical and ultrastructural features of the interface formed by different biotypes of saxicolous lichen species with their rock substrata were investigated in the semiarid habitat of the SE Iberian Peninsula and the relationships between the bioweathering patterns observed and lichen colonization selectivity towards the different rock substrata evaluated. Xanthoria parietina was able to fix to the rock substratum by the adherence of single cell walls from the lower cortex. Neofuscelia pulla used rhizines and loose groups of hyphae for attachment of the thallus to the rock. Colonization by the foliose lichen species was confined to the rock surface, while Diploschistes diacapsis was also able grow below the surface showing two types of hyphal growth. Minerals in close contact with cell walls were biochemically and biophysically weathered, but hyphae showing calcium oxalate crystals did not appear to be directly involved in the patterns observed. The textural characteristics of the substratum seemed to be related to the type of microorganism colonization: sedimentary rocks were more deeply colonized by lichens and other chasmolithic microorganisms than volcanic material. Calcium oxalate crystals were found in the medulla of N. pulla but not at the lichen-substratum interface. Crustose lichens such as D. diacapsis showed calcium oxalate crystals in the upper cortex and over the outside of fungal medullary hyphae but not in direct contact with the rock surface. Calcium oxalate precipitation seems to be related to the different metabolic activities of the mycobiont within the lichen thallus and to different species. D. diacapsis inhibits the growth of other microorganisms in close proximity to the thallus, whereas foliose species were associated with several communities of microorganisms.

Oxalate production by fungi: its role in pathogenicity and ecology in the soil environment

1996 ◽  
Vol 42 (9) ◽  
pp. 881-895 ◽  
Author(s):  
Martin V. Dutton ◽  
Christine S. Evans
Keyword(s):  
Oxalic Acid ◽  
Calcium Oxalate ◽  
Cell Walls ◽  
Divalent Cations ◽  
White Rot ◽  
Lignocellulose Degradation ◽  
Calcium Oxalate Crystals ◽  
Copper Salts ◽  
Oxalate Crystals ◽  
Oxalate Secretion

Oxalate secretion by fungi provides many advantages for their growth and colonization of substrates. The role of oxalic acid in pathogenesis is through acidification of host tissues and sequestration of calcium from host cell walls. The formation of calcium oxalate crystals weakens the cell walls, thereby allowing polygalacturonase to effect degradation more rapidly in a synergistic response. There is good correlation between pathogenesis, virulence, and oxalic acid secretion. Solubility of soil nutrients is achieved by soil-living species, when cations freed by oxalate diffusing in clay layers increases the effective solubility of Al and Fe. Oxalate retained in hyphal mats of mycorrhizal species increases phosphate and sulphate availability. The formation of calcium oxalate crystals provides a reservoir of calcium in the ecosystem. The ability of oxalate to bind divalent cations permits detoxification of copper, particularly evident in wood preserved with copper salts. Oxalate plays a unique role in lignocellulose degradation by wood-rotting basidiomycetes, acting as a low molecular mass agent initiating decay. In addition, in white-rot fungi oxalate acts as a potential electron donor for lignin-peroxidase catalysed reduction and chelates manganese, allowing the dissolution of Mn3+from the manganese–enzyme complex and thus stimulating extracellular manganese peroxidase activity. The biosynthesis and degradation of oxalate are discussed.Key words: oxalic acid, calcium oxalate, pathogenicity, fungi.

An SEM study of raphide crystal initials in the leaves of vitis (grape)

1995 ◽  
Vol 53 ◽  
pp. 984-985
Author(s):  
H. J. Arnott ◽  
M. A. Webb ◽  
L. E. Lopez
Keyword(s):  
Calcium Oxalate ◽  
Water Soluble ◽  
Calcium Oxalate Crystals ◽  
Calcium Oxalate Crystal ◽  
Oxalate Crystals ◽  
Large Numbers ◽  
Sem Study ◽  
The Matrix ◽  
Crystal Cells ◽  
Crystal Idioblast

Many papers have been published on the structure of calcium oxalate crystals in plants, however, few deal with the early development of crystals. Large numbers of idioblastic calcium oxalate crystal cells are found in the leaves of Vitis mustangensis, V. labrusca and V. vulpina. A crystal idioblast, or raphide cell, will produce 150-300 needle-like calcium oxalate crystals within a central vacuole. Each raphide crystal is autonomous, having been produced in a separate membrane-defined crystal chamber; the idioblast''s crystal complement is collectively embedded in a water soluble glycoprotein matrix which fills the vacuole. The crystals are twins, each having a pointed and a bidentate end (Fig 1); when mature they are about 0.5-1.2 μn in diameter and 30-70 μm in length. Crystal bundles, i.e., crystals and their matrix, can be isolated from leaves using 100% ETOH. If the bundles are treated with H2O the matrix surrounding the crystals rapidly disperses.

Oxalic acid and calcium oxalate produced by Leucostoma cincta and L. persoonii in culture and in peach bark tissues

1987 ◽  
Vol 65 (9) ◽  
pp. 1952-1956 ◽  
Author(s):  
J. A. Traquair
Keyword(s):  
Oxalic Acid ◽  
Calcium Oxalate ◽  
Crystal Morphology ◽  
Culture Media ◽  
Positive Staining ◽  
Acid Solutions ◽  
Calcium Oxalate Crystals ◽  
Oxalate Crystals ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes

Oxalic acid and crystals of calcium oxalate were produced during growth of Leucostoma cincta and L. persoonii on potato dextrose agar and in peach bark tissues. The identification of calcium oxalate was based on solubility characteristics, the results of KMnO4 titration, positive staining with silver nitrate – dithiooxamide, and crystal morphology as observed with light and scanning electron microscopes. Oxalic acid was detected by gas chromatography. This is the first report of oxalic acid production by both Leucostoma species causing peach canker. Calcium oxalate crystals observed on or near hyphae in culture were similar to crystals in artificially inoculated peach bark tissues. Addition of oxalic acid solutions alone to inner bark tissues caused maceration and necrosis. These results indicate a role for oxalic acid in the early stages of pathogenesis by Leucostoma spp. Tetragonal (bipyramidal) and prismatic calcium oxalate crystals formed on bark wounds treated with oxalic acid solutions were similar to those observed in infected tissues and in culture media amended with oxalic acid.

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