By planting the cuttings of sweet potato stems with single node and leaf each, and by removing the lateral buds perfectly after rooting, the author got simplified plants, which showed no simptoms of physiological disturbances for about 50 days. The artificial leaf spots caused by 0.05 per cent KClO3 with 0.01 per cent eosin were able to use as the modified leaf spots caused by Phyllosticta batatas and Macrosporium bataticola, especially the latter, in the pahtophysiological point of view. With application of these simplified plants and artificial leaf spots, the author studied whether the physiological disturbances of the spotted leaves would be recovered or not. His data were summarised in Figures 1 to 4. When the spots appered successively, as it was shown in Fig.1 pathphoysiologic disturbances showed 2 types: (a) Phyllosticta spotted leaf (13 to 25 per cent necrotic) was accompanied by the increase in respiration and the decrease in assimilation, which continued for a long time keeping a balance between them though it was abnormal. (b) Macrosporium spotted leaf (16 to 32 per cent necrotic) was accompanied by the increase in respiration which followed by sudden decrease. The assimilation rate at first increased began to decrease and finally dropped down that of the healthy and the leaves lost the sign of life. When the KClO3 spotted leaf (24 per cent necrotic) or the Phyllosticta spotted leaf (16 per cent necrotic) occured only one time and the spreading of the necrotic area stopped soon after, as it was shown in Fig. 2, both of the increase in respiration and the decrease in assimilation are gradually restored to healthy. The artificial leaf spot caused by KClO3 spread again and formed concentric ring, if water drops were given on this spot, and the increase in respiration and the decrease in assimilation reappeared (Fig. 3). Fig. 4 showed the assimilation and respiration curves of the KClO3 spotted leaves with large (15~25mm in diam.) but few (4~5) spots and small (3~5 mm in diam.) but many (30~35) spots each indicated 31~43 per cent and 17~20 per cent necrotic respectively. In such spotted leaves, the increase in the respiration converted to decrease with several days and followed by the depression of the assimilation until no measurable values could be obtained. The author concluded that the data indicated the recovery from the physiological disorder of the spotted leaves given by Figures 2 and 3, suggested the availability of spraying fungicides not only as the preventives but also as the therapeutics.
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