Identification of phosphate granules occurring in seedling tissue of two palm species (Phoenix dactylifera and Washingtonia filifera)

Abstract

Haustoria of two palm species, Phoenix dactylifera L. (date) and Washingtonia filifera (Lindl.) Wendl were carefully dissected from seeds, and the ultrastructural characteristics of the large, electron-opaque granules present in the cells of this tissue were compared using standard aldehyde and OsO4 fixations. In Washingtonia, the granules were smaller than those in date and were more variable in size and presence of non-opaque inclusions. All granules appeared to be membrane bounded although they often filled the bounded space. No protein, lipid, carbohydrate or tannins were found in the granules by standard staining procedures. The granules stained positively with two different metallic-phosphate stains which contained either bismuth or lead. Energy dispersive X-ray microprobe analysis, done on aldehyde-fixed granules and those stained with both phosphate stains, confirmed the fact that phosphorus and calcium were present in the granules. The granules also bound the metallic stains as expected. All procedures consistently confirmed the presence of phosphate in the granules. The data are most consistent with the hypothesis that the granules are composed of polyphosphate.

Seed structure and histochemistry in the palm Euterpe edulis

“…The cotyledon of two palm species, P. dactylifera and W. filifera , exhibited electron‐opaque granules identified by EDX analysis as polyphosphate deposits (DeMason & Stillman, 1986). Such granules were not identified in embryo tissues of the species in this study.…”

Recent Discoveries on the Roles of Polyphosphates in Plants

“…Among multicellular eukaryotes, acidocalcisomes have been found in human platelets (Ruiz et al 2004). Likewise, a membrane-bound organelle within the protein storage vacuole of plant seeds, the globoid, is similar to the acidocalcisome (DeMason and Stillman 1986;Jiang et al 2001). The globoid shared several characteristics of the acidocalcisome, including its electron-dense appearance, acidic matrix, high concentration of phosphate compounds (insitol polyP, phytate), and presence of a vacuolar pyrophosphatase and an aquaporin in its surrounding membrane (Jiang et al 2001).…”

Identity and functions of inorganic and inositol polyphosphates in plants

“…Using TEM, polyP bodies appear as electron-dense granules, and they have been observed in palm seeds and rice anthers (DeMason & Stillman, 1986;Mamun et al, 2005). One way to determine the composition of these granules is by combining electron microscopy with energy-dispersive X-ray microanalysis.…”

“…One way to determine the composition of these granules is by combining electron microscopy with energy-dispersive X-ray microanalysis. This technique allows for the detection of atoms based on their emission spectra upon X-ray excitation, and it has been used to analyze the composition of polyP granules in bacteria (Alvarez & Jerez, 2004) and plants (DeMason & Stillman, 1986;Otegui et al, 2002).…”

“…In the green lineage, the presence of significant polyP stores has been firmly established in algae (Werner et al, 2007a;Aksoy et al, 2014), while the microscopy and biochemical extraction methods used in the early studies on higher plants are now known to lack specificity towards polyPs (Keck & Stich, 1957;Miyachi, 1961;Tewari & Singh, 1964). The identity of the polyP bodies reported in plant TEM sections has likewise not been validated by other methods (DeMason & Stillman, 1986;Mamun et al, 2005). We have recently used a polyP-specific dye and a polyP-binding protein to detect polyPs in plants in a genetically validated manner .…”