Embryo- und Endospermentwicklung nach einer Röntgenbestrahlung der Fruchtknoten von Arabidopsis thaliana (L.) heynh

Abstract

After X-ray irradiation (56 kV, 2 mA, filter 0·1 mm Al) of the pistils in Arabidopsis thaliana and subsequent pollination of the stigmata with non-irradiated pollen, the following aberrations can be observed, except for normal fertilization: on the one hand, the caryogamy between female and male nucleus may be inhibited, on the other, dispermous or trispermous fertilization of the ova may take place. Compared to the controls, the embryos of the ovules show different stages of development after irradiation of the pistils. The widest range of variation was observed eight days after pollination. With increasing dose the number of embryos developing decreases. Degenerations are only detectable after several divisions of embryo and endosperm; the cells of the embryo proper degenerate earlier and more often than those of the suspensor. Numerous embryos develop only into the globular stage. Up to the early globular stage the development of the embryo is independent of that of the endosperm. From the fourth day after pollination aberrant divisions can be observed in the suspensor. An increase in divisions running vertically to the longitudinal axis of the embryo often results in an abnormally increased number of suspensor cells. Additional divisions running parallel to the longitudinal axis lead to flattened or bulky suspensors. If only a few cells of the suspensors are involved in these divisions, the division products will often be similar to embryos in the quadrant stage. Compared to the controls, the number of endosperm nuclei is reduced after irradiation of the pistils. Degeneration of the endosperm is more like to occur with high doses than with low doses.