Elemental composition and X-ray diffraction studies of Strobilanthes species

Fernandes, Maria Cineola ; Sellappan, Krishnan

Abstract

Strobilanthes Blume is a member of family Acanthaceae. Energy Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) analysis were carried out on leaf and stem of ten species of Strobilanthes collected from the Northern Western Ghats (Maharashtra and Goa), India. The overall elemental composition of leaf and stem showed the presence of 10 elements (C, O, Mg, Cl, Si, Ca, K, S, Al and Fe). Al and Fe were detected only in S. callosa, S. integrifolia and S. ixiocephala. Elemental composition (atom percentage) varied among the species of Strobilanthes. Cystoliths constitute the characteristic feature of this family which also possesses different forms of Calcium Oxalate (CaOx) crystals such as raphides (needle-shaped) and styloids (prismatic). XRD analysis of leaf and stem samples revealed similar patterns of diffraction with two broad maxima arising from amorphous forms of; silicon oxycarbide & silica and calcium oxalate; along with a calcite peak and minor reflections from calcium oxalate crystals, suggesting the co-existence of both amorphous and crystalline mineral phases which could be of taxonomic importance. Although the functions of cystoliths and Calcium Oxalate crystals are not completely known, they play an important role in physical protection against grazing, biochemical functioning of plants including the photosynthetic process.

Keyword(s)

Cystoliths; EDS; Mineral phase; Raphides; Strobilanthes; XRD

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