Cryosectioning of plant material frozen at high pressure



Low-temperature electron microscopy combined with electron diffraction allows determination of the state of structural preservation as well as that of the solidified cellular water in frozen-hydrated sections. Apple leaves frozen at high pressure and cryosectioned with glass knives covered with a very thin layer of frozen water exhibit a minimum of artefacts and are thin enough for structural analysis. The Zeiss 902 EM energy-filtering microscope helps to improve the poor contrast of frozen-hydrated sections by imaging in the zero-loss mode. All sections analysed showed the electron diffraction pattern of vitreous water. This is ideal: the character of the liquid phase is preserved. A very high yield of good cryosections is achieved because the samples are vitrified and the friction on the glass knife surface is reduced by a thin ice layer.