A new technique of plant analysis to resolve iron chlorosis
Iron though indispensable for the biosynthesis of chlorophyll, its total content in the plant was not associated with the occurrence of chlorosis. In order to overcome this inconsistency a new technique of plant iron analysis has been developed. It consists of the determination of Fe2+, the fraction of iron involved in the synthesis of chlorophyll.
The choice of 1–10 o-phenanthroline (o-Ph) as an extractant for Fe2+ was based on its remarkably higher stability constant for Fe2+ than Fe3+. On this basis, it could preferentially chelate Fe2+. The highly specific organce colour of the Fe2+-phenanthroline complex made possible the determination of Fe2+ by reading the transmittancy at 510 nm.
The procedure involves extraction of 2 g of thoroughly washed, chopped, fresh plant by 20 ml of o-phenanthroline extractant (pH 3.0, conc. 1.5%). The plant samples treated with the extractant are allowed to stand for 16 hours and Fe2+ is determined in the filtrate by reading the transmittancy at 510 nm.
In sharp contrast to total iron the green plants always contained more Fe2+ than chlorotic plants. The technique has been developed for rice but is expected to be successful for other crops also.
Key WordsFe2+-iron Iron chlorosis o-Phenanthroline
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