斑点性病害

In these experiments, artificial leaf spots were produced on leaves of the sweet potato by puncture inoculations of KClO_3 (0.05 % water solution). Both the diseased and healthy leaves growing on the same plants were weighed (dry) in the morning and evening to determine the difference of the degree of increase in dry weight. This was done for the purpose of studying the pathophysiological disturbances of the diseased leaves and their effects on the healthyones. My findings in the experiments are as follows. 1) When plants with a single leaf are subject to half-leaf inoculation, the larger the number of leaf spots, the greater the degree of patho-physiological disturbances in the healthy halves (Fig. 2). Patho-physiological disturbances reach a maximum in from one to three days for the diseased halves, and in two days for the healthy halves. When the diseased halves are restored equally to healthy, their physiological activities showed an increase after seven days (Fig. 1). If the plants were cultured in their normal habitat, the physiological disturbances, induced by the leaf spots were comparatively slight (Fig. 3). 2) When plants of five leaves are subject to half-leaf inoculation in each leaf, the patho-physiological disturbance in the disease halves gradually increased until the leaves lose all sign of life. In the healthy halves, on the other hand, the patho-physiological disturbances reached a maximum three to five days after inoculation. When restored to health, they then show increased physiological activity after a lapse of ten days (Fig. 4). 3) In plants of sixteen to eighteen leaves t h e physiological activities of older leaves are very weak. If, in these plants, only the center leaf is diseased, two leaves above and one below begin to show patho-physiological slight disturbances, but the physiological activities of the older leaves were somewhat recovered again. The diseased leaf loses signs of life seven to a days after inoculation (Fig. 5). 4) If, in a pl a n t with two leaves, one of the leaves is diseased in several degree, the healthy leaf is also subject to patho-physiological disturbances. The degree to which it disturbed is somewhat influenced by the severity of injury, but is not as evident when compared with that of a single leaf plant. (Figs. 6 and 7). 5 ) In three, six, eight or ten leaf plant, in which all but one leaf are diseased, the degree of the patho-physiological disturbance of the healthy leaf is proportionate to the number of the existing diseased leaves, but little relation is had with that of the diseased leaves themselves. It sometimes happen that when the diseased leaves are numerous, the patho-physiological disturbances are greater in the healthy leaf than in the diseased ones. The greater the number of diseased leaves the later the maximum disturbance appeared in the diseased leaves. But such a phenomenon is not as remarkable in the healthy one (Figs. 8, 9, 10 and 11). 6) Using plants of five leaves each, a different numbers of leaves were inoculated with the same total number of spots in one experiment. In another experiment, plants with varying numbers of diseased leaves with also varying number of total spots were examined. As a result, it was found that the number of diseased leaves bear more effect on the degree of patho-physiological disturbance in the healthy leaves than the proportionate total number of leaf spots (Figs. 12 and 13). 7) If in a plant with two branches, all the leaves on one branch are diseased, patho-physiological disturbance occurs even in the leaves of the healthy branch, but the degree of injury of diseased leaves seemes to bear little influence on the physiology of the healthy ones (Figs. 14 and 15).