C5-P-02Distribution of intercellular spaces in plant seeds during imbibition and germination observed using X-ray micro-CT

Abstract

Plant seeds resume their physiological activities during imbibition, but little is known regarding the associated structural changes because in vivo analysis is difficult. We employed X-ray micro-computed tomography (micro-CT) to investigate the inner structures of seeds [1]. Tomograms of the seeds of various plant species with an effective pixel size of about 2.4 μm were obtained using micro-CT equipment in BL20B2 at SPring-8. The energy of the X-ray beam was set to 10 keV. The 3-D relationship of the structures inside the seeds in these tomograms was examined using IMOD software. We could examine the spatial distribution of Ca oxalate crystals in Lotus miyakojimae seeds using this method [2]. This method also enabled us to examine the development of air spaces in the embryo during maturation and germination. To clarify the function of air spaces in seeds, we investigated air space distributions in the seeds of various species. Intercellular spaces were not detected in dry seeds, but were developed during imbibition in L. miyakojimae seeds, one of enforced dormant seeds. In contrast, intercellular spaces were detected in the embryos of dormant seeds of lettuce, tomato, and arabidopsis. It is possible that the intercellular spaces in the dormant seeds supply the oxygen required for the low and high rates of metabolism during dormancy and germination, respectively. This work was partly supported by a grant from Hyogo Science and Technology Association. Experiments were performed with the approval of JASRI (Proposal nos 2012A1364, 2012B1158 and 2014A1306). [1] Y Mineyuki, Microscopy 63 (2014) Suppl 1: i8-i9. [2] D Yamauchi et al, Microscopy 62 (2013) 353-361. C5-P-01 doi:10.1093/jmicro/dfv329