Non-destructive determination of manganese state in rice leaf by X-ray absorption spectrometry

Abstract

Abstract One of the authors analyzed the brown spot symptoms developed on plant leaves caused by nutritional disorders using an X-ray Micro-Analyser (Sasaki et al. 1980). The use of an X-ray Fluorescence Element Mapping Spectrometer (XEMS) revealed that external and internal stresses such as X-ray irradiation and manganese excess induced the transport of manganese, and excess of manganese concentration as cationic Mn2+ was related to the formation of the abnormal brown spots (Watanabe and Kobayashi 1986; Watanabe et al. 1988). Since, the mechanism of the transport of manganese remains to be elucidated the analysis of the chemical state of manganese in plant is important. Since the valency of manganese readily changes depending on the redox potential, non-destructiye analysis may be effective. In fact, few studies have been carried out on the non-destructive determination of the manganese state in plant tissues. We studied the state of manganese in rice leaf in performing Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) analyses by X-ray Absorption Spectrometry with syncrotron radiation as the analytical source. X-ray absorption spectrometry provides structural information about the local surroundings of a metal ion, the binding configuration, etc. The concept and method of analysis were reviewed in detail by Teo (1981). The advantage of these methods over the previous methods is reported and the state and transport of manganese in leaf are discussed.