Der Einfluß einer variierten K‐Ernährung auf die Inkorporierung von markiertem Stickstoff (15N) bei jungen Sonnenblumen (Helianthus annuus L.)

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Abstract
The effect of a varied K nutrition upon the incorporation of labelled nitrogen (15N) in young sun flower plants (Helianthus annuus L.)1. The influence of the potassium nutritional status upon the incorporation of labelled nitrogen (15N) into the soluble amino fraction and into the protein fraction was studied with young sun flower plants (Helianthus annuus L.). The plants were cultivated in a solution culture with 3 different nitrogen and 2 different potassium levels. During the last 24 hours of this cultivation the nitrogen of the nutrient solution was labelled by 15N‐nitrate in the various treatments.2. The growth of the plants was affected considerably by the various nutritional treatments. The yield of the plant matter increased with increasing nitrogen supply. This nitrogen effect was enhanced by the better potassium nutrition.3. The contents of soluble amino compounds in roots and upper plant parts increased with the increasing nitrogen application. This tendency was reduced by the higher potassium supply. The contents of protein nitrogen rose with the nitrogen nutrition. Potassium reduced the content of protein nitrogen in treatments with high growth rates.4. Related on a single plant the incorporation rate of nitrate nitrogen into the organic matter was higher in plants with a good potassium nutritional status than in plants with a low potassium nutritional status. This effect was especially evident in the treatments with the highest nitrogen supply. Here the nitrate incorporation rate was 5–7 times higher with the higher potassium application.5. This favorable effect of potassium upon the assimilation of nitrate nitrogen was also evident, if the incorporation rate was not related to a single plant, but on the unit of weight of plant material (fresh matter). Thus with high nitrogen supply the quantity of labelled nitrogen of the amino fraction was about 2 times higher in the plants with a high potassium nutritional status compared with plants of a low potassium nutritional status. In the protein fraction this potassium effect was still more evident. The influence of potassium upon the nitrate nitrogen assimilation was the better the better the plants were supplied with nitrate.

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