Incorporation of15N into subcellular fractions and soluble proteins in rice seedlings

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Abstract
UN incorporation into the subcellular and protein fractions of rice seedlings was investigated, when (15NH4)2SO4 was fed through culture solution, and the following was found. (1) Optical emission spectroscopic method is very useful for the 15N analysis of small amount of protein as much as separated by Sephadex 0-200. (2) In the developed leaves, where nitrogen was balanced by continuous influx and efflux, 6 to 9 percent of total nitrogen was exchanged in a day by newly absorbed nitrogen, and the absorbed nitrogen was incorporated into chloroplast, 30,000 × g precipitate and soluble protein fractions by almost equal rates. (3) In the developing leaf, where the amount of nitrogen was increasing, newly absorbed and redistributed nitrogen almost equally contributed to the increase of total and protein nitrogen. (4) The speed of 15N incorporation into Fraction 1 Protein was the same in the developing leaf and slow in the developed leaves in comparison with other soluble proteins.