Effects of Water-Absorbing Rate of Seed on Flooding Injury in Soybean

Abstract

Soybean seeds are known to be sensitive to flooding stress. It has been proposed that a rapid inrush of water into soybean seeds causes physical disruption of seeds leading to a marked reduction in seedling emergence and subsequent seedling growth. However, when the water-absorbing rate of seeds was osmotically reduced by submerging the seeds into PEG solution, no damage occurred. Submersion of the seeds in PEG solution at least for 48 hr did not cause any damage. Imbibition of seeds in PEG solution up to 70% seed moisture level (dry weight basis) completely protected seed from the flooding injury in subsequent soaking in water. These results indicate that the flooding injury can be avoided by reducing the rate of water absorption during the early stage of seed hydration, and that the injury is mainly caused by physical damage of seeds and not by oxygen deficiency. However, when germinated seeds with visible radicles emerged were soaked in water, seedling emergence and subsequent growth were markedly reduced as when dry seeds were soaked in water. This injury of germinated seeds may be physiological damage due to oxygen deficiency. Thus, in the studies on flooding injury of soybean, the effect of flooding during germination (imbibition) and after radicle protrusion should be examined separately.