Silica in Woody Stems

Abstract

Scanning electron microscopy has been used to examine silica isolated by chemical means from the wood of 32 species of woody perennial. The silica consists of aggregate grains lying free in the lumina or in ray and xylem parenchyma cells in 24 of the species. It occurs as dense silica in the other species, filling the lumina or lining the internal surfaces of vessels (and fibres) in all cases except Gynotroches axillaris where it is deposited in ray parenchyma cells. Infrared spectra and X-ray diffraction diagrams, obtained for specimens of both sorts of silica, are indistinguishable from those for amorphous silica. Aggregate grain and dense silicas are also alike in that their differential thermal analysis curves show a rather broad endothermic peak between 175° and 205°C. The results are discussed in relation to possible modes of deposition of the two sorts of silica and the tendency for silica in ray parenchyma cells to be associated with polyphenols.

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

“…For each sample from the natural transects, the phytolith index d/p, a proxy of tree cover density (Alexandre and Bremond, 2009;Bremond et al, 2005b), was calculated. It is the ratio of Globular granular phytolith category (Madella et al, 2005) formed in the secondary xylem of the dicotyledon (d) wood to the grass short cell phytolith category formed in the epidermis of grasses or Pooideae (p) (Collura and Neumann, 2017;Scurfield et al, 1974;ter Welle, 1976). Those two categories make up most of the phytolith assemblages recovered from inter-tropical soils (Bremond et al, 2005a, b;Alexandre et al, 1997Alexandre et al, , 2013.…”

“…Three repeated counting gave an error of ±3.5 % (SD). Phytoliths were named using the International Code for Phytolith Nomenclature 1.0 (Madella et al, 2005) and categorized as Globular granulate type produced by the wood (Scurfield et al, 1974;Kondo et al, 1994), palm Globular echinate type and grass types comprising Acicular, Bulliform, Elongate psilate, Elongate echinate, Bulliform cells, and Grass Short Cells types. For each sample from the natural transects, the phytolith index d/p, a proxy of tree cover density (Alexandre and Bremond, 2009;Bremond et al, 2005b), was calculated.…”

“…(e.g., Collura and Neumann, 2017). In the wood, silica polymerizes in the secondary xylem supposedly unaffected by transpiration, in the form of Globular granulate phytolith types (Madella et al, 2005;Scurfield et al, 1974;ter Welle, 1976). These phytoliths make up more than 80 % of tropical humid forest and rainforest phytolith assemblages found in soils and sediments (Alexandre et al, 1997;Alexandre et al, 2012).…”

Structural studies of tabasheer, an opal of plant origin

“…For example, plants in acidic soils with available aluminium show damage to root systems, which become stunted and brittle (Birchall 1990). The mechanisms of the exclusion of aluminium are not well understood and the speciacion of Al, by contrast to that of Si, which has been extensively studied in connection with zeolite synthesis (Barrer 1982), is highly complex, especially in dilute solutions and pH close to neutral (Sigel and Sigel 1988). It appears that the environmental balance of Al and Si may be of considerable biological consequence.…”

“…Brewster (1828). Silicon, at 20 at.%, is the most abundant element in the Earth' s crust after oxygen; silicon is an essential trace element and is present, normally in small concentrations, in all living organisms (Lewin and Reimann 1969, Scur® eld et al 1974, Bendz and Linquist 1978, Simpson and Volcani 1981, Mann et al 1983, Raven 1983, Ciba Foundation 1986, Sigel and Sigel 1988, Simkiss and Wilbur 1989, Birchall 1990). …”