Diaspore

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diaspore

[′dī·ə‚spȯr]
(mineralogy)
AlO(OH) A mineral composed of some bauxites occurring in white, lamellar masses; crystallizes in the orthorhombic system.

Diaspore

 

a mineral, natural aluminum hydroxide, AIOOH; contains 85 percent AI2O3 and 15 percent H2O, often with impurities of iron, chromium, manganese, and gallium oxides. Diaspores crystallizes in a rhombic system, forming lamellar, sometimes acicular, crystals. Its color is white, yellowish or pinkish white, or greenish gray. Its hardness on the mineralogical scale is 6–7; its density varies depending on the content of impurities, from 3,300 to 3,500 kg/m3. When annealed it becomes α-Al2O2 (corundum).

Diaspore is mainly concentrated in bauxites, where it appears as an ore-forming mineral together with boehmite and gibbsite. In association with corundum and chloritoids, it is found in emery deposits that are produced by the metamorphic change of bauxites. Diaspore is found in metamorphic, hydrothermic; and metasomatic deposits of the secondary quartz type.

References in periodicals archive ?
Viability of the diaspore bank was not tested with tetrazolium chloride because the diaspores are tiny and tender and also enclose dry and hard fruits.
The mathematical models used to describe the hygroscopicity of pequi diaspores, for most of its coefficients, showed significance of regression at 0.01 level by t-test (Table 2).
Fruiting periodicity depends principally on flowering, but it is also influenced by environmental conditions appropriate for fruit development, diaspore dispersal, and seedling establishment (Rathcke and Lacey, 1985; Ibarra-Manriquez et al., 1991; van Schaik et al., 1993).
coriaceum diaspores are large and potentially dispersed by hoarding rodents, such as agouti (Dasyprocta spp.), and this vertebrate has already been named one of the main dispersers of another species of the same genus (Caryocar brasiliense Camb.) (Gribel, 1986).
According to Van der Pijl (1982), the richness and spatial distribution of plant populations are determined by dispersal modes and the frequency the diaspores reach favorable locations for the establishment of seedlings.
Seed entrapment in alpine ecosystems: effects of soil particle size and diaspore morphology.
2-a breeding system that promotes self-pollination, 3- a floral morphology that allows a large diversity of floral visitors, 4- a generalist biotic pollination system or wind pollination, and 5- seed dispersal syndromes of diaspores with the capacity to colonize distant areas.
Natural riparian zones are also effective pathways for plant dispersal: the rivers carry large numbers of plant diaspores over long distances (Schneider and Sharitz 1988, Nilsson et al.
Morphology and dispersal of one- and two-seeded diaspores of Cryptantha flava.
It was hypothesized that the model assumptions germination rate increases linearly between Tb and To and decreases between To and Tc; Tb is similar for all seeds in the population; and Tc varies with seeds-are met for braquiarao diaspores.
Fruits with no epi- and mesocarp, from now on referred to as diaspores, are the dispersion units of this species (MORAES and PAOLI, 1996), and are produced in large quantities and characterized as tolerant to desiccation (LIMA et al., 2008).Although the conservation status of the species is considered "common" (OLIVEIRA-FILHO, 2006), it appears in the FAO list, as elaborated in the "Panel of Experts on Forest Gene Resources", as a priority for genetic conservation (ROCHE, 1987).