On the Experiments of Germination and Absorption-Power of Water in the Seeds of Rice as a Method of Estimation of Drought-Resistance among the Varieties of Rice-Plants

摘要

Studiesa of bsorption-opwer (Saugkraft in German) of seeds as a criterion of drought-resistance in various crop plants have hitherto been made by several investigators. The present author has made experiments with germination and absorption of water in rice-seeds in oder to estimate the varietal drought-resistance in the plant. In his many previous experiment on the drought-resistance of rice plant, the up-land and low-land varieties were chiefey used as materials, but in the present study there wore added to them another kind of varieties, the "intermediate rice" (Kan-to in Japanese, which is nursed in the early stages of growth after the dry farming methods and in the later grown in the same manner as low-land rice, the variaties being cultivated in Korea from old times. The drought-resistance of these varieties had been determined by the same method as the author reported previously, that is, the plant were cultivated on up-lands and low-lands respectively, thrice in three years, and their responce to these conditions in growth and yield were compared; moreover, the developments of the stereomes-the mechanical tissues-in leaves of these varieties were anatomically investigated. Now, it had been reported by some authors, that the seed of up-land rice can germinate in the soils of lower moistures compared with that of low-land rice. In the aurthor's experiments, as far as the soil moistures were 10%, 15% 20% and 30% in the weight of air-dried loam soil, the same relation as mentioned above was observed among certain special varieties; but, among the other varieties, the contrary evidence was also observed. In the varietal comparison of germination capacity and velocity, several methods of treatment of the results were considered: among which were calculated Gassner's "Wertungszahl" -namely the percentage of germination (K%) divided by the mean number of days for germination, or K% divided by the number of days of testing. But, as these known methods generally proved not so suitable for exact expression of germination velocity, the author preferred a new criterion, so-called "Mean energy of germination", which is calculated as the total sum of germination percentages in each days, divided by the number of days of testing- namely ΣK%/No. of days, and according to the results, it was showed clearly that there exists no practical relation between the grade of drought-resistance and the velocity of germination of seeds in various moisture contents of soils. On the other hand, the author conducted experiments on germination under various temperatures 10', 15°, 20°and 25°C., with seeds fully presoaked in cold water of temperatures 0' to 5°C. In this case, it was generally observed that the seed of the variety whose germination was more rapid in low moisture of soils, germinated more rapidly under the lower temperatures. And these facts seemed to indicate that such a method as Wertungszahl that is combined by two factors, the percentage of germination and the mean date of germination or number of days required for germination, is not suitable for estimation of drought-resistance, because those factors are directly affected by the temperature of testing. In regard to the results of the cxperiments on the water-absorbing-power of seeds under the temperatures, 0°, 5°, 10°, 15°and 20°C., distinct differences among the varieties were observed, but there was found, too, no correlation between the velocity of absorption of water or the total amount of water absorbed and the drought-resistance. And moreover, the variation of the germination velocity in each variety corresponding to different temperatures did not related to its resistance. After all, the author was unable to determine the drought-resistance of rice plants by means of testing the germination or water absorption power of the seeds.