Although 3D distribution of air spaces inside seeds can be detected in vivo using X-ray micro-computed tomography (CT) [1, 2], where the source of the air that gets trapped in those intercellular spaces during imbibition remains unknown. To resolve this question, we observed seed imbibition processes continually using the BL20B2 beamline at the SPring-8 facility. A seed of Lotus miyakojimae in a filtered-pipette tip containing distilled water was set on the sample stage and was rotated (0.4 rpm) continually for 90-min. A series of 21,600 images with an effective pixel size of approximately 2.75 μm was acquired and 72 time-lapse tomograms were reconstructed. Results showed the appearance of intercellular spaces in the embryo after the disappearance of the void spaces around the embryo in the imbibed seed suggesting that the air was taken up from outside to the embryo during imbibition.
Changes in the void space in and around the hypocotyl (H) of a Lotus .miyakojimae seed during early imbibition. CT images were obtained at 1 min 15 sec (A), 15 min (B), and 50 min (C) after the start of image acquisition. Arrows, void spaces; arrowheads, intercellular spaces.
1. Y Mineyuki, Microscopy 63 (2014) Suppl 1: i8-i9.2.
2. D Yamauchi et al, Microscopy 62 (2013) 353-361.
The synchrotron radiation experiments were performed at the BL20B2 of SPring-8, with the approval of the the JASRI (Proposal Nos. 2017B1225, 2018B1182and 2019A1130).
