The Cytological Mechanism of Biparental Cytoplasmic Inheritance in Pelargonium hortorum -Ultrastructural and DNA Fluorescence Studies of Male and Female
Abstract:Electron microscopic investigation has demonstrated that plastids and mitochondria are conserved in the generative cell, sperm cells and egg cell of Pelargonium hortorum Bailey. The plastids in the generative cell which contain starch for a short period, gradually changed to proplastids during the maturation of generative cell. The plastids in the sperm cells are large and numerous the characteristics of dense matrix and an abundant endomembrane systems. These plastids always appear ringlike in cross section. In the generative cell and sperms, the spherical or rod-shaped mitochondria are smaller than the.plastids and remain unchanged during the development process from generative cell to sperm cells. DNA filaments are visualized in the transparent central zone of the mitochondria. In the egg cell, plastids are more abundant than mitochondria. The structures of the plastids and mitochondria are obviously different from those in the sperm cell. Most of the plastids are irregularly rod-shaped and contain starch, the mitochondria are about 3 times larger than those in the sperm cells. Most of them are cup-shaped as proved by successive sections. DNA epifluorescence study demonstrated that DNA nucleoids are present in both plastids and mitochondria of the egg, generative cell and sperm cells. In the sperm cells, there is no ringlike DNA nucleoid as is existed in the egg cell. This study has defined the characteristics of the plastids and mitochondria in both male and female gemates of P. hortorurn. The results are essential contributions for further investigation of the biparental organelle transmission in the zygote and proembryo.