Characterization of Calcium Oxalates Generated as Biominerals in Cacti

Abstract

The chemical composition and morphology of solid material isolated from various Cactaceae species have been analyzed. All of the tested specimens deposited high-purity calcium oxalate crystals in their succulent modified stems. These deposits occurred most frequently as round-shaped druses that sometimes coexist with abundant crystal sand in the tissue. The biominerals were identified either as CaC 2 O 4 .2H 2 O (weddellite) or as CaC 2 O 4 .H 2 O (whewellite). Seven different species from the Opuntioideae subfamily showed the presence of whewellite, and an equal number of species from the Cereoideae subfamily showed the deposition of weddellite. The chemical nature of these deposits was assessed by infrared spectroscopy. The crystal morphology of the crystals was visualized by both conventional light and scanning electron microscopy. Weddellite druses were made up of tetragonal crystallites, whereas those from whewellite were most often recognized by their acute points and general star-like shape. These studies clearly demonstrated that members from the main traditional subfamilies of the Cactaceae family could synthesize different chemical forms of calcium oxalate, suggesting a definite but different genetic control. The direct relationship established between a given Cactaceae species and a definite calcium oxalate biomineral seems to be a useful tool for plant identification and chemotaxonomy.Calcium oxalate is considered to be the most commonly occurring biomineral in higher plants (for example, see reviews of Arnott and Pautard, 1970; Franceschi and Horner, 1980; Arnott, 1982). It has been demonstrated that crystal growth is a highly controlled intracellular process (Mann, 1989; Fraú sto de Silva and Williams, 1991; Baran, 1995). The cells in a plant tissue that produce the crystals are generally referred to as crystal idioblasts (Foster, 1956; Arnott, 1982).Calcium oxalate occurs in two hydration states in plants, as the monohydrate (whewellite) or as the dihydrate (weddellite; Frey-Wyssling, 1981; Arnott, 1982). A number of crystal habits have been found for both hydration states: raphids, prisms, styloids, druses, and crystal sand (Franceschi and Horner, 1980; Arnott, 1982). Other less common shapes could be considered as variations of the mentioned forms. Both the chemical nature and the morphology of these crystals, as well as their localization within the plant body, could be specific for a given species. Some higher plants may accumulate enormous quantities of inorganic material, and this is especially true for some members of the Cactaceae family (Franceschi and Horner, 1980). For example, as early as in 1938, a cactus species (Cactus senilis) was described as containing as much as 85% of its dry weight as calcium oxalate (Cheavin, 1938).We described recently the isolation and characterization of biominerals from two different Cactaceae species. This bioinorganic material appears in the form of highly pure and well-crystallized calcium oxalates that typically grow in the form of druses, i.e. s...

Trichomes with crystals in the Cephalocereus Pfeiff. areoles

“…Members of the Cactaceae family are not an exception, as crystals have been observed in the stems, roots, and fl owers, mainly in the cells of the fundamental tissue (Terrazas and Mauseth, 2002;Hartl et al, 2007). Crystals have been documented in the hypodermis of Opuntia species (Conde, 1975;Monje and Baran, 2002;Tovar-Puente et al, 2007) and in wood the crystals are rare (Gibson, 1973). There are also reports of crystals in stem epidermal cells of various genera of the subfamily Cactoideae, where they vary in shape and number.…”

IR - spectroscopic characterization of biominerals in marattiaceaeus ferns

“…unfortunately, it was not possible to arrive to an unambiguous identification of the chemical nature of the calcium oxalate found in these plants on the basis of the only relatively well defined oxalate IR band (located at 1641 cm -1 in the A. pruinosa sample and between 1641 and 1658 cm -1 in the spectra of the other species) one could tentatively suggest the presence of weddellite (pure weddelite band is found at 1645 cm -1 whereas in whewellite it is found at 1622 cm -1 (Monje & Baran, 1996, 1997). Furthermore, the low frequency spectral range which usually allows a clear differentiation between the two calcium oxalate forms (Monje & Baran 2002), appears partially overlapped by one of the typical sio 2 bands and is highly undefined. a clearly different iR spectrum was obtained when one of the milled samples, or a dry sample of the plant material, was slowly heated in a muffle furnace up to 400 °C and then maintained for 2 hours at this temperature ( figure 1B).…”

Moving carbon between spheres, the potential oxalate-carbonate pathway of Brosimum alicastrum Sw.; Moraceae

“…Where Ca 2+ can then react with oxalic acid to form calcium oxalate as either mono-or di-hydrate crystals (Verrecchia 1990;Verrecchia et al 2006) acidic soil environments. At current, investigations have confirmed 24 species are associated with active OCPs Cailleau et al 2004;Cailleau et al 2014;Ferro 2012;Garvie 2003Garvie , 2006Monje and Baran 2002), typically utilising the emblematic localised alkalinisation of acidic soils as a geochemical proxy for oxalogenesis. The most heavily investigated OCP is associated with Milicia excelsa Welw.…”

“…Oxalic acid can then be converted into insoluble CaOx crystals (K sp ≈ 10 −8.5 ; Certini et al 2000;Monje and Baran 2002;Palak et al 2012) by plants within specialised cells called crystal idioblasts (Faheed et al 2013;Franceschi and Nakata 2005;Nakata 2002Nakata , 2003. These CaOx crystals are subsequently released during herbivory and decomposition, creating a CaOx pool adjacent to the producing species, in its rhizosphere (Cailleau et al 2011;Jayasuriya 1955), stomachs of endopedonic species (Bassalik 1913), or within phytoabrasions Verrecchia et al 2006).…”