The effects of salt concentration of culture solution and calcium supplied to the soil on the occurrence of the marginal rot in Chinese cabbage (Brassica pekinensis RUPR.)

Abstract

In the first experiments reported here, the authors attempted to solve the question whether or not the concentration of soluble salts in culture solution is an accurate index of the occurrence of marginal rot in Chinese cabbage.Plants grown in the solution A containing anions such as chloride and nitrate at high level suffer from leaf marginal rot in the position between 10th and 20th leaves and from the blackening of hydathodal tissue in the position between 20th and 30th leave counted from the bottom up. Therefore, the occurrence of marginal rot may be connected with a disturbance of water-relation due to the cell degeneration. When the heading begins, physiological activity such as mineral absorption becomes higher, but the fullness in tissue decreases. This apparently indicates that there is an unbalanced metabolism in the head of Chinese cabbage during the heading stage.The rate of growth increased in proportion to the concentration of the culture solution. It is therefore difficult to relate the occurrence of marginal rot to high osmotic pressure of culture solution. On the other hand, the solutions of single salt in 0.2 molar concentration led to decrease in the rate of absorption of water, the physiological drought, but did not produce the marginal rot.The second experiment was designed to clear up the effect of calcium supplied to the soil on the CaO content in leaves and on the occurrence of the physiological disorder. The symptom of marginal rot occurred when CaCl2 and Ca(NO3)2 of high rate were applied to the soil. Although the calcium content was high in lower leaves and low in the upper leaves, there was no direct relationship between the occurrence of the marginal rot and the total calcium content.It seems possible that the marginal or heart rot in Chinese cabbage is a symptom of the relative calcium deficiency and not due to the physiological state produced by the failure of calcium absorption. The conclusion, therefore, is that the calciumm content in younger leaves lies between those of the calcium-deficient and normal leaves, and other factors such as osmotic pressure and/or specific ions enhance the occurrence of the marginal rot in the leaves of Chinese cabbage.