Abstract
1. In this paper describes the results of studies on the effects of hydrogen-ion concentration in the juices of the stems and leaves of the Udo salad plant and in the plants belonging to the genus Aralia on the development of the atrophic fire-blight disease in the Udo salad plant (Aralia cordata THUNB.) causing Phoma Araliae COOKE et MASSEE var. microspora WATANABE.
2. The extent of hydrogen-ion concentration in the juices of the stems and leaves of the Udo salad plant and in plants belonging to the genus Aralia seems to have no particular effect on the development of the present disease.
3. In the development of the present disease, no special relation could be recognized between the extent of the hydrogen-ion concentration in the juices of the stems and leaves of the Udo salad plant and in the plants belonging to the genus Aralia and the extent of hydrogen-ion concentration on the growth of mycelia and germ-tubes from the pycnospores of the causal fungus.
4. From the above mentioned results, the agronomic or regional varieties and strains of “Kan-Udo” were susceptible as well as the agronomic or regional varieties and strains of “Haru-Udo” were most resistant to the present disease, such results are impossible depend upon the hydrogen-ion concentration of the stems and leaves of the host plant.
