A third type of raphide crystal in the plant kingdom: Six-sided raphides with laminated sheaths in Agave americana L.

Abstract

Raphides in leaves of Agave americana L. have six-sided cross sections. Each crystal tapers off to a point at both ends. It is enveloped in a 100 nm thick sheath which, in cross section, shows lamellae with periods of 6-9 nm. No polysaccharides could be detected in the sheaths with the Thiéry reaction. Dissolution of a raphide in acid occurs slowly from both ends leaving the crystal sheath visible in the light microscope. The raphide cell walls contain a layer that in glutaraldehyde-fixed tissue reacts neither with the Thiéry stain nor with potassium permanagnate. Its morphology resembles the "isotropic layer" of Chafe and Chauret (Protoplasma 80, 129-147, 1974) but no lignification could be shown as yet. Though up to now only raphides with four-sided or H-shaped cross sections have been observed by electron microscopy, we suggest that many raphides described as "rounded" in light microscopy might in fact be six-sided.

New and unusual forms of calcium oxalate raphide crystals in the plant kingdom

“…The characteristic appearance, development and distribution of raphides, as well as other crystal shapes, have been used for taxonomic, pharmacognostic and toxicological purposes (Horner et al 2012; Lampe and Fagerström 1968; Metcalfe and Chalk 1957; Sakai and Hanson 1974). Several studies have been conducted to elucidate the development and formation of raphides and raphide-containing idioblasts (Frey 1929; Horner and Whitmoyer 1972; Kausch and Horner 1983a; 1983b; 1984a; Mollenhauer and Larson 1966; Parameswaran and Schultze 1974; Sakai and Hanson 1974; Tilton and Horner 1980; Wattendorff 1976). Bruni et al (1982) have described raphide formation as a complex process involving several cellular compartments.…”

Anatomia foliar de quatro espécies do gênero Cattleya Lindl. (Orchidaceae) do Planalto Central Brasileiro

“…Em todas as espécies analisadas, de modo particular em C. nobilior, ocorrem idioblastos com ráfides de oxalato de cálcio, o que vem a corroborar as referências sobre a família (Metcalfe 1963;Wattendorff 1976;Franceschi & Horner 1980;Kauschik 1982;Pridgeon 1982;Campos Leite & Oliveira 1987;Ferreira 1992;Widholzer 1993;Leiria 1997). Mauseth (1995) acredita que o oxalato de cálcio contribui para tornar as plantas menos palatáveis aos animais, frisando, no entanto, que a função do oxalato na biologia vegetal é questão ainda controversa.…”

Three Systems of Biomineralization in Plants with Comments on the Associated Organic Matrix

“…In many raphide-forming cells the sheath may become multilayered (12,35,38). A complex system is associated with the production of calcium oxalate crystals in the crystal vacuole.…”

“…Pentecost (27) has defined matrices as "substances which assist in the initiation, and control the direction of, crystal growth"; he also points to the difficulty in deciding the extent to which substances are active and the exact site of their activity. (2,7,12,14,25,31,35,38). With isolated crystals (4,6), it is possible to correlate studies with light microscopy (LM), scanning electron microscopy (SEM), and X-ray diffraction.…”