in situ Fourier Transform Infrared Spectroscopy of Cellular Properties of Mature Embryos of Omap Rice Species

The Oryza genus contains diverse and complex plant characteristics, including seed behavior during dehydration. The protein secondary structure, glassy matrix, and membrane phase behavior of dried embryos may be associated with the acquisition of desiccation tolerance. We used in situ Fourier transform infrared (FTIR) spectroscopy to investigate the properties of dry embryos.

IR spectra of the dried Oryza spp. embryos, including 2 cultivated and 11 wild species, showed that a-helical conformations were the major protein secondary structures, and the composition of conformation components was stable after heating of all dried seeds. Embryos showed similar and reasonable T_g values, even those of the recalcitrant O. coarctata, as well as O. punctata, and O. granulate, with their low germination rate. However, the lipid phase of orthodox species was mainly in the liquid crystalline phase at room temperature, whereas that of O. coarctata, O. punctata, and O. granulata remained in the gel-liquid phase at freezing temperature. Lipid behavior but not protein composition/structure or glassy matrix status might be a useful index of embryo tolerance to desiccation.