Spectrophotometric Estimation of Nucleic Acid of Plant Leaves

Abstract

A procedure is described for extracting and estimating the RNA and DNA content of leaves and leaf fractions. Extraction was by a modified Schmidt-Thannhauser procedure. The amounts of RNA and DNA, in terms of P, were estimated from the UV absorption of the extracts. Phosphate analysis of RNA extracted from bean (Phaseolus vulgaris) agreed with estimates based on the UV absorption. The extracted DNA, on the other hand, contained only about 75% as much phosphate as the UV absorption and diphenylamine reaction indicated. The difference was accounted for by an amount of phosphate, presumably from interpurine linkages, that remained with the protein after the hydrolysis and separation of DNA with 0.5N perchloric acid (70[degree]C, 15 minutes). Total phosphate in the whole nucleic acid-protein fraction of bean leaves was equal to the sum of the RNA and DNA, separated and estimated spectrophotometrically. Values are given for the amounts of RNA and DNA found in bean leaves, cotyledonary leaves of Raphanus sativus, and chloroplasts of Spinacea oleracea.