Multi-elemental analysis of roots and leaves from Oryza glaberrima rice plants at vegetative stage of growth by combined PIGE, RBS, PIXE and GC-TDS methods

Abstract

This study aims at understanding the bioaccumulation and transport mechanisms of both micronutrients and macronutrients in the leaves and roots of African rice Oryza glaberrima Steud (OG) plants cultivated in Senegal during the wet season at the vegetative stage of growth and to evaluate the suitability of OG rice plants for phytoremediation. A comparative analysis of the elemental composition of roots and leaves of OG plants, provided information on the bioaccumulation of nutrients necessary for plant growth which can become detrimental if their toxicity level is reached. The elemental analysis of basic nutrients (C, H, O), macronutrients (N, P, K, Ca, Mg and S) and micronutrients (Cl, Fe, Cu, Mn, Ni and Zn) in the OG roots and leaves was made possible by several elemental analytical techniques (PIGE, RBS, PIXE and GC-TDS). All methods were validated by analysis of pure substances and certified reference materials. The high accumulation rate of Cu (5 x), Al (4 x), Zr (≥ 2 x) and Fe (~ 2 x) in the OG rice roots relative to the leaves indicates the existence of low translocation factors for these metals from root to leaves probably due to the existence of plant mechanisms to limit their transport and to preferentially accumulate Si (5.2 ± 0.5 % mass) in the rice leaves. The high accumulation rates of Cr, Mn, Ni and Rb in the OG leaves relative to the roots, and of Al, Fe, Cu and Zr in the OG roots relative to the leaves, shows that these metals can be partially removed from soil through phytoextraction processes by harvesting the shoot and root tissues.