Zur Entwicklung der Kalium‐Mangelsymptome von Sommerraps

The development of potassium deficiency symptoms in summer rape Macroscopic, microscopic and chemical investigations of summer rape plants, grown under glass at different levels of potassium, led to the following results. 1. Marginal and intervenal chlorosis of sucessive leaves as well as withering and darkgreen colour can be considered as the early symptoms of potassium deficiency in rape. 2. Chlorosis appears often (especially in cases of slight potassium deficiency) first of all in the middle leaves and later in the old leaves. 3. With plants, recieving normal amounts of potassium, the highest concentration of potassium is found in the old leaves and the lowest in the young. Only in cases of acute deficiency is this reciprocal. 4. The potassium deficiency symptom sequences, given in the literature, appear to be dubious, since the causal relationship, hitherto accepted, between the appearance of collapsed cortical tissue, the enlargement of parenchyma cells and secondary cambium activity does not exist. 5. The cambium activity in the stalk with potassium deficiency and so the formation of xylem and phloem is greatly damaged. The formation of structural elements, such as sclerenchyma fibres and woody parenchyma cells, however, is especially affected by this deficiency. 6. There are indications that stem necrosis, described as a typical potassium deficiency symptom, is primarily related to parasitic infection favoured by potassium deficiency.