Ultrastrukturelle Veränderungen der Kernmembran von Lepidium sativum L. in der Mitose

Abstract

The ultrastructural changes of the nuclear envelope from nuclei in the root cortex of Lepidium sativum L. during mitosis was analysed by means of freeze etching techniques and by series of ultrathin sections. It could be shown with the electron microscope that in contrast to the well known light microscopic fact of the “break-down” of nuclear envelope during late prophase nuclear double membranes are split into pieces. These, however, don't loose their structural characteristics (e.g. nuclear pores) during meta- and anaphase.
The diameter of nuclear pores and their number per square micron of nuclear envelope is changed during single phases. It seems likely that the relative pore area per nuclear surface is constant (cf. Wunderlich 1969). The nuclear envelope of telophase nuclei consists of pore containing remnants of the parental nucleus and pore-free parts of the new incorporated ER membranes. This miscellaneous character of the nuclear envelope is lost during further stages of telophase.
These results are discussed in respect to some autonomy of the nuclear envelope and under the aspect of the possible role of nuclear membrane as controlling the rate of DNA synthesis (Alfert and Das 1969).