Water uptake and distribution in germinating lupine seeds studied by magnetic resonance imaging and NMR spectroscopy

Magnetic resonance imaging (MRI) was used to study temporal and spatial water uptake and distribution in germinating lupine ( Lupinus luteus L.) seeds. During 24 h of imbibition, water was unevenly distributed within the seed and some anatomical parts were more hydrated than others. Water entered the seed through the hilum and micropyle. The embryonic axis was the first to show hydration followed by seed coat and later cotyledons. The changes in water status were characterized by NMR spectroscopy. Analyses of T₂ relaxation times revealed a three-component water proton system (structural, intracellular and extracellular water) in germinating lupine seeds. The data on the components of transverse relaxation time studies indicated the complex exchange processes taking place between water components inside lupine seed over first 2.5 h of hydration, with a distinguished increase in structural water and decrease in other components. This speaks in favor of the high water-absorbing capacity of lupine seeds as related to high protein content. Germination was accompanied by swelling of protein bodies and changes in the organization of stored reserves with gradual disappearance of protein from the cells.