Role of Seed Coat in Imbibing Soybean Seeds Observed by Micro-magnetic Resonance Imaging

Abstract

Background and AimsImbibition of Japanese soybean (Glycine max) cultivars was studied using micro-magnetic resonance imaging (MRI) in order to elucidate the mechanism of soaking injury and the protective role of the seed coat.MethodsTime-lapse images during water uptake were acquired by the single-point imaging (SPI) method at 15-min intervals, for 20 h in the dry seed with seed coat, and for 2 h in seeds with the seed coat removed. The technique visualized water migration within the testa and demonstrated the distortion associated with cotyledon swelling during the very early stages of water uptake.Key ResultsWater soon appeared in the testa and went around the dorsal surface of the seed from near the raphe, then migrated to the hilum region. An obvious protrusion was noted when water reached the hypocotyl and the radicle, followed by swelling of the cotyledons. A convex area was observed around the raphe with the enlargement of the seed. Water was always incorporated into the cotyledons from the abaxial surfaces, leading to swelling and generating a large air space between the adaxial surfaces. Water uptake greatly slowed, and the internal structures, veins and oil-accumulating tissues in the cotyledons developed after the seed stopped expanding. When the testa was removed from the dry seeds before imbibition, the cotyledons were severely damaged within 1·5 h of water uptake.ConclusionsThe activation of the water channel seemed unnecessary for water entry into soybean seeds, and the testa rapidly swelled with steeping in water. However, the testa did not regulate the water incorporation in itself, but rather the rate at which water encountered the hypocotyl, the radicle, and the cotyledons through the inner layer of the seed coat, and thus prevented the destruction of the seed tissues at the beginning of imbibition.

Modeling of the water absorption during the steeping of yellow peas

“…The Robin boundary condition (Eq. (9) in this study), or the first order increase in the case of the Hsu (1983) model, describes the contribution of the seed coat of peas in controlling the rate of water absorption during imbibition to prevent soaking injuries (Kaptso et al, 2008;Koizumi et al, 2008;An et al, 2010).…”

Grain Legumes

“…In adzuki bean, in contrast, water entry was delayed by c. 7 h, and the slow hydration was required to activate the lens. In soybean, water entered near the raphe, diffused first towards the dorsal side of the seed and then to the hilar region, followed by expansion of the radicle and hypocotyl and later by swelling of the cotyledons (Koizumi et al 2008). In soybean cultivars in which seed-coat permeability is due to cracks in the seed cuticle, permeability of isolated seed coats was five times lower in hard-seeded compared to soft-seeded cultivars, as measured by pressure probe ).…”

“…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). Thus, cultivars within the same species might differ in the seed-coat ports involved in initial water uptake.…”

Biosynthesis and Characterization of ZnO Nanoparticles from Spinach (Spinacia oleracea) Leaves and Its Effect on Seed Quality Parameters of Greengram (Vigna radiata)

“…This might be due to the enhancement of the growth hormones in seed by the treatment of different concentrations of Zinc oxide nanoparticles [29]. However, at higher concentration, the growth of root and shoot was found to decline.…”