Morphological and quantitative changes in the population of cell organelles during microsporogenesis of Pinus sylvestris L. I. Morphological changes from zygotene until prometaphase I.

The membrane-like structures in the nucleus, the nuclear pore, the disappearance of the nuclear membrane, the synaptinemal complex, and changes in the nucleolus and karyoplasm are described and discussed. Plastids and mitochondria do not change during the microsporogenesis. Until diplotene the lipid granules with electron transparent vesicles are arranged into a “lipid complex”. During pachytene rough endoplasmic reticulum changes into smooth endoplasmic reticulum. During diplotene numerous Golgi bodies are present. Microtubules are present from zygotene and scattered in the cytoplasm. At diakinesis many vesicles appear. Ribosomes as well as polysomes are present. From diakinesis only ribosomes are observed. Callose wall formation starts in diplotene and is connected with the presence of many smooth endoplasmic reticulum cisternae and Golgi vesicles, probably also with polysomes and lipid granules.