Structural changes in membranes of developing wheat embryos during the acquisition of desiccation tolerance.

Abstract

AbstractTo elucidate possible structural changes in membranes with drying, in relation to the acquisition of desiccation tolerance and to correlate the loss/maintenance of membrane integrity during drying with membrane structure, immature wheat (cv. Prioskskaya) embryos in the desiccation-sensitive and -tolerant stages of their development were subjected to in vivo electron spin resonance spin probe techniques. Up to 15 days after anthesis (DAA), embryos increased in length as a result of cell division, followed by dry weight accumulation, with the main weight gain between 15 and 22 DAA. Some desiccation-tolerant cells were found in wheat embryos as early as at 14 DAA, the proportion of which gradually increased with developmental age up to 17 DAA. Germination after drying and rehydration was observed for the first time at 18 DAA. Not all cells in wheat embryos acquired desiccation tolerance simultaneously. To correlate acquisition of desiccation tolerance with possible changes in membrane fluidity, the membrane spin label, 5-DS, was applied. While the spectra of perdeuterated oxo-tempo in cytoplasm or oil bodies were isotropic, those of 5-DS were anisotropic. Comparison of 5-DS spectra obtained from 14 DAA and 20 DAA embryos showed that the proportion of the mobile component increased after the acquisition of desiccation tolerance, indicating that membranes were more rigid in dried wheat embryos at the desiccation-sensitive stage than at the desiccation-tolerant stage.