ON THE GERMINATION OF BEAN SEEDS(PHASEOLUS)DURING SOAKING IN WATER

Abstract

Kidney bean seeds were soaked in tap water filtrated through the ion exchange resin. No bean seeds germinated in water. The moist seeds which had been swollen before soaking in water by placing them on moist absorbent cotton at 25℃ for 24 hours or at 2℃ for 96 hours germinated during soaking process by passing air through the water in which the seeds were soaked. The seeds were soaked in water before the radicle protruded. BARTON(1950)confirmed that carbon dioxide prevented the harmful effects of soaking. It was shown, however, that exposure of the moist seeds to air excluded carbon dioxide during soaking process resulted similarly in germination in water. In this case, cracking occurred in the radicle somewhat. The temperatures of pretreatment which caused the moisture content of seeds to increase had no influence on the germination during soaking process. Air-dry seeds which had decreased in moisture content by placing them in a desiccator with calcium chloride were soaked in water in the same manner. In this case, in spite of passing air through the water in which the seeds were soaked, no seeds germinated during soaking process or after removing them from water. The germinative capacity of the dry seeds was prevented by soaking them in non-aerated water at 25℃ for a short period. Soaking in non-aerated water at 25℃ for 74 hours prevented also the germinative capacity of the moist seeds. Moist and dry seeds were soaked at 25℃ for 72 hours in water varying from 0.5 to 3.0cm in depth. The moist seeds which were soaked in water 0.5 cm deep, a portion of a seed being exposed to the air, germinated during soaking process, but the dry seeds germinated neither during soaking process nor after removing them from water. Soaking in water more than 1.5cm in depth prevented the germinative capacity of all seeds. The quantity of oxygen which dissolved in non-aerated water in which the seeds were soaked was very small after soaking at 25℃ for 72 hours. The condition free from oxygen impeded the germinative capacity of the moist seeds after 72 hours. KIDD and WEST(1919)stated that there were three plausible hypotheses for the dereterious effects of soaking bean seeds ; 1. Disorganized metabolism resulting from deficiency in oxygen supply and accumulation of carbon dioxide ; 2. Leaching out of essential soluble food reserve ; and 3. A combination of 1 and 2. They did not think it was due to the lack of oxygen. ALBAUM(1940)showed that exposure of oat seeds to an excess of oxygen during soaking resulted in abnormal germination. BARTON(1950)described that any disorganization of the metabolism of the seed was not due to either to a deficiency in oxygen supply or to an accumulation of carbon dioxide, but rather the reverse might apply. The experimental results described in the present paper show that the injurious effects of long-continued soaking in water on the germination of the moist seeds which have increased their moisture contents before soaking in water are ascribed to deficiency in oxygen supply, but as for soaking of the dry seeds, the other factors are harmful to their germination. It seems that the soaking injury of the dry seeds occurs as a result of cracking of the seeds by rapid absorption of water and a loss of essential cell constituents during the soaking periods.