Einfluß von K-Ernährung und Mehltaubefall auf den N-Haushalt von Sommergerste während des Kornwachstums

Influence of K nutrition and mildew attack on N metabolism of spring barley during grain development Spring barley cv Aramir was grown in complete nutrient solutions containing 0,4 (K₁) and 4 me K/l (K₂) respectively. Half of the plants were sprayed regularly with a fungicide, the other half became naturally infected by mildew, Erysiphe graminis. Mildew attack was clearly visible in unsprayed plants, especially at K₁. Accordingly also grain yield was depressed by 18% (K₁) and 15% (K₂) compared to the controls. Better K nutrition reduced symptoms of mildew infection drastically and increased grain yield from 87 g/pot (K₁) to 169 g (K₂). Similar yield increases (106 to 199 g/pot) were obtained in the control plants, revealing that under the experimental conditions better K supply stimulated growth in general rather than inducing specific defense mechanism against the pathogen. The latter was hoped to be detectable by applying ¹⁵N-nitrogen during 3 days at anthesis. Although K₂ plants absorbed more ¹⁵N and incorporated more ¹⁵N into leaf protein, this cannot be considered as a K induced defense reaction. Instead due to lower grain yields in infected plants less proteolysis in the vegetative plant parts occured.