A new technique of plant analysis to resolve iron chlorosis
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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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