Ultrastructure of pollen development in Euphorbia dulcis L. 1. Diploid plants

Ultrastructual development from microspores at the tetrad stage up to the bicellular stage of pollen of diploid Euphorbia dulcis L. was investigated. At the tetrad stage the microspores are enclosed by a thick callose wall. The nucleus occupies a central position in the microspore, is nearly spherical and shows a distinct nucleolus. The thin primexine varies in thickness. Large plastids with starch grains are present. The generative cell becomes separated from the inline and changes into two short “tails”. Many long rough endoplasmic reticulum (RER) cistemae are arranged parallel to the plasmalemma in the tail parts. Plastids are not present. Microtubules are parallel to the plasma membrane of the generative cell. In the vegetative cell, the plastids undergo two amylogeneses. The first occurs at the tetrad stage and the second after the first pollen mitosis, when the generative cell starts to move to the central position in the vegetative cell. Many lipid droplets surround the generative cell. RER is arranged in aggregations near the generative cell. After the first mitotic division the inline forms a network of microfibrillar substances around the pores. The cell wail, separating the vegetative and generative cell, is regularly interrupted by plasmodesmata or plasma channels.