Drought Resistance and Constancy of Osmotic Ascension caused by Wilting in Soybeans

Abstract

In the former reports (33) the authors affirmed in soybean plant, as other plants (1, 13, 23, 29, 31, 32, 37, 38, 41'), the one grown on drought spot has higher osomtic value than the one grown on moist place. But they observed that the temporary drought resistance, which acquired on extremely dry spot in hot season, relaxates in cool season. Fortunately some of these samples were studied to see the regulation of osmotic value by subjecting them to wilting. Temporary wilting is believed to give the plant drought resistance (16, 42), like the temporary cold resistance (30,31,35,39,40).Whether the experience of former drought, which has influenced to increase the cell sap concentration (6, 7,34,36,43) still effects osmotic ascension or not on the part produced from the growing point after the soil moisture is regained is a problem not yet investigated. Material and MethodsThe material is a autumn-soybean Tamanishiki which is the same in Rep. 1. The plants were grown in cyrindric, galvanized iron pats 15 cm in diameter and 17 cm height. The soil used was sandy loamm and the saturated water capacity of this soil was estimated approximately 26%. A watering tube containing crushed stone extended down the side of each pot to the bottom. The pots were divided into two groups of 80% and 50% of water capacity, and the pots were weighed daily and adjusted by watering. The pot of 80% water capacity which had been subjected to wilting stopped being watered, and in several days it reached near the point of permanent wilting. After that the soil was once more watered to regain the optimum soil moisture, 80% of water capacity. The results (Fig. 1) are described in the former report (33).