Observations on water distribution in soybean seed during hydration processes using nuclear magnetic resonance imaging

Water in seeds plays an important role not only in physiological but also in chemical processes. In addition to the requirements of water for germination, seeds of legumes used for human consumption require hydration to prepare them for cooking. The site of water entry, however, and its movement during imbibition in legumes and particularly in soybean is still not clear. One of the best and most precise methods of tracing water movement in plant tissue is nuclear magnetic resonance (NMR) imaging. In our study, we applied NMR imaging to reveal the water distribution in soybean seeds during the first 24 h of hydration. It has been found that hydration during this period is a multistage process. Water enters the seed through the micropyle and hilum and the concentration of water there is very high during the entire imbibition process. Inside the seed, water first fills the voids between cotyledons, and between the cotyledons and the seed coat. Water then enters the embryonic axis, and from it, is distributed into cotyledons. The highest water concentration after 24 h of imbibition was observed in the embryonic axis. The external part of the cotyledons was hydrated at a slower rate than the internal tissue. Key words: Soybean, Glycine max L., nuclear magnetic resonance imaging, water imbibition, water distribution