Calcium Oxalate Crystals in Eucalypt Ectomycorrhizae: Morphochemical Characterization

Abstract

Ectomycorrhizal fungi are ubiquitous in forest ecosystems, benefitting plants principally by increasing the uptake of water and nutrients such as calcium from the soil. Previous work has demonstrated accumulation of crystallites in eucalypt ectomycorrhizas, but detailed morphological and chemical characterization of these crystals has not been performed. In this work, cross sections of acetic acid-treated and cleared ectomycorrhizal fragments were visualized by polarized light microscopy to evaluate the location of crystals within cortical root cells. Ectomycorrhizal sections were also observed by scanning electron microscopy (SEM) coupled with energy dispersive x-ray (EDS) microprobe analysis. The predominant forms of crystals were crystal sand (granules) and concretions. Calcium, carbon and oxygen were detected by EDS as constituent elements and similar elemental profiles were observed between both crystal morphologies. All analyzed crystalline structures were characterized as calcium oxalate crystals. This is the first report of the stoichiometry and morphology of crystals occurring in eucalypt ectomycorrhizas in tropical soils. The data corroborates the role of ectomycorrhizae in the uptake and accumulation of calcium in the form of calcium oxalate crystals in hybrid eucalypt plants.

Chemical and Physical Mechanisms of Fungal Bioweathering of Rock Phosphate

“…Whewellite (CaC 2 O 4 ÁH 2 O) is hydrated calcium oxalate, and as a monohydrate, it is more stable than its dihydrate form (weddellite) and one of the most common forms of oxalate encountered in the environment (Gadd 1999;Gadd et al 2014). In terrestrial environments, calcium oxalate crystals are commonly found associated with fungi, and many species are capable of their formation due to secretion of oxalic acid: both weddellite and whewellite have been recorded (Fomina et al 2010;Gadd 1999Gadd , 2017bGadd et al 2014;Pylro et al 2013). In our experiments, the source of the calcium was primarily from the apatite component of the RP, confirming that the whewellite product results from the interaction between the fungus and the apatite, following the equation:…”

Role of mycorrhizas and root exudates in plant uptake of soil nutrients (calcium, iron, magnesium, and potassium): has the puzzle been completely solved?

“…Empirical studies have shown that Ca is important in the formation, maintenance, and function of AM fungi (Jarstfer et al., 1998; Khabou et al., 2014; Kosuta et al., 2008; Liu, et al., 2013b; Navazio & Mariani, 2008; Piao et al., 2016) including being involved in AM fungal signaling pathways to facilitate fungal penetration of root tissues (Chabaud et al., 2011). The presence of EM fungi improves availability of metal elements, as indicated by greater Ca uptake in temperate forests, in which there is strong leaching of Ca from silicate minerals as a result of its release from apatite (Blum et al., 2002; Pylro et al., 2013), and AM also increase K and Ca uptake as a result of the greater volume of soil explored (Ruan et al., 2013). Although studies of the effects of mycorrhization on plant Fe uptake are limited, mobilization of Fe and Si is positively correlated with hyphal length (Van Hees et al., 2004) and mycorrhization is positively associated with plant Fe concentrations (Ibiang et al., 2017), indicating that mycorrhizas enhance plant Fe uptake.…”

Qr Code Como Ferramenta De Divulgação Científica De Dados Botânicos No Parque Pedra Da Cebola, Vitória-Es

“…Nas plantas, esses cristais funcionam como depósitos intravacuolar e suas diferentes funções são discutidas. A função biológica dos cristais de CaOx nas plantas ainda não é completamente compreendida(PYLRO et al, 2013). Apesar da fonte de reserva de cálcio ser a função mais atribuída, a mobilidade deste íon para a translocação do floema nas plantas é pequena e os cristais de CaOx serem encontrados em órgãos a serem descartados, o que sugere que estes estejam envolvidos no metabolismo de excreção excessiva de cálcio nas plantas(PAIVA, 2019).…”