[Investigations on the distribution of manganese between cell fractions from spinach leaves]

1. Spinach was harvested once a week, beginning five weeks after sowing. The leaves were divided into three categories, according to their height of insertion. For every category, Hill-activity and manganese content (by atomic absorption) were measured. The remaining leaf material was homogenised in distilled water or in a mixture of 0.6 M sucrose and 0.05 M Tris/maleate buffer, pH 7.8, and the homogenate was separated by differential centrifugation into two fractions: a green precipitate consisting mainly of chloroplast fragments and a yellow supernatant. Chloroplast fragments, isolated in sucrose medium, were washed with distilled water. Manganese and nitrogen content of the precipitate and the supernatant were determined, as was the chlorophyll concentration of the precipitate. 2. The manganese content in the old leaves and their fractions increased; nitrogen concentration, chlorophyll concentration, chlorophyll/nitrogen and chlorophyll/manganese ratios decreased. 3. The lowest inserted leaves and their fractions had a different chemical composition from the rest: they had a higher manganese and a lower nitrogen content. The chlorophyll/nitrogen ratio of the lamellae was also higher. 4. At the beginning, the lowest inserted leaves had the same manganese content as the seeds. Then the manganese concentration decreased slightly and increased again when leaf decomposition began. 5. We found a chlorophyll/manganese ratio of 104 molecules chlorophyll to 1 atom manganese. 6. Hill activity decreased with increasing age of the shoot. It seemed to be a function of the shoot age rather than the leaf age. 7. The manner of preparation had an effect on the chlorophyll/dry weight ratio, but not on the manganese/dry weight and nitrogen/dry weight ratios. Therefore the manganese/chlorophyll and the chlorophyll/nitrogen ratios depended on the manner of preparation.