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

Abstract

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.

Ascorbate and glutathione metabolism in embryo axes and cotyledons of germinating lupine seeds

“…During seed desiccation AsA gradually decrease and dry seed are completely devoid of it (De Gara et al 1997). However, NMR studies of temporal and spatial water uptake and distribution in germinating lupine seeds showed the existence of areas with elevated local moisture content and free water in dry seeds (Garnczarska et al 2007) and that may partially explain the presence of AsA in dry lupine seeds. LeubnerMetzger (2005) showed that in air-dry tobacco seeds local elevation in moisture content was enough to permit de novo β-1,3-glucanase expression.…”

Grain Legumes

“…In other grain legumes, the primary region of water entry is the lens, as in Lupinus albus (Perisse and Planchuelo 2004) and azuki bean ( Vigna angularis; Isemura et al 2007), or the hilum and micropyle as in Lupinus luteus (Garnczarska et al 2007). In soybean, the lens is the main port of water entry (Koizumi et al 2008), but in cultivars with nonfunctional lens water uptake takes place through cuticular cracks in the seed coat (Ma et al 2004).…”

Differential response of antioxidative enzymes in embryonic axes and cotyledons of germinating lupine seeds

“…On the contrary, in cotyledons the level of free radicals did not change significantly during germination and also SOD activity was unaltered. It seems that differences in free radicals production and SOD activity between embryo axes and cotyledons are not related to the fact that both organs hydrate to different extents, as shown by NMR analysis (Garnczarska et al 2007), since the increase of SOD activity in embryo axes was observed shortly before or immediately after radicle protrusion i.e., at the time when both embryo axes and cotyledons were well hydrated. Comparative analyses of hydration patterns, free radical generation and antioxidative metabolism in germinating pea also showed that the differences in the resumption of metabolic activity between embryo axes and cotyledons appear to be more closely related to metabolic and developmental processes associated with preparation for germination than with variation in hydration per se (Wojtyla et al 2006).…”

“…In the mature dry lupine seeds the water content is low, not exceeding 9%. However, magnetic resonance imaging showed the existence of areas with elevated local moisture content in dry lupine seeds (Garnczarska et al 2007). The structures and enzymes necessary for the initial resumption of metabolic activity are generally assumed to be present within dry seed, having survived, at least partially intact, the desiccation phase that terminates seed maturation.…”