Lens: Water Channel for Dry Broad Bean Seeds at Germination Observed by Micro-Magnetic Resonance Imaging
[1]
Mika Koizumi , Research Institute for Science and Engineering, Waseda University, Tokyo, Japan.
[2]
Hiromi Kano , Oak-Hill Georgic Patch-Work Laboratory, Chiba, Japan.
Water permeation into dry broad beans (Vicia faba) was tracked by micro-magnetic resonance imaging (MRI) using water molecules absorbed in the seeds as a tracer, in order to clarify the function of the lens at germination. Image changes of broad bean seeds during imbibition were continuously measured at 15-min intervals by single-point imaging (SPI) method using a 300 MHz NMR spectrometer of a superconducting magnet and with an imaging attachment. A rather long period (8 h) was required to activate a water channel after steeping the seeds. Water entered the seed through the lens in the end opposite the hilum and slowly migrated to the radicle-hypocotyl axis through the seed coat. The cotyledons swelled after water reached the radicle-hypocotyl axis. The seeds were vital on wet filter papers, and differentiation of vasculature in the cotyledons was detected 2 days after measurement. The current investigation is a visualization of the hypothesis that the first softened tissue is the lens as water enters dry seeds, and water is delivered through testa to the radicle-hypocotyl axis for some leguminous species (e.g., broad bean) to germinate.
Broad Bean (Vicia faba), Germination, Lens, Magnetic Resonance Imaging, Seed Coat, Water Uptake
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