Colobanthus quitensis (Kunth) Bartl, produced two types very small bisexual flowers. In the Antarctic natural conditions chasmogamic and cleistogamic flowers most often form five stamina with short filaments. Two microsporangia with a three-layer wall form in the anther. Microspore mother cells, which develop into microspores after meiosis, form inside the microsporangium. Microsporocytes of Colobanthus quitensis are surrounded with a thick callose layer, the special wall. After meiosis, the callose wall is dissolved and microspores are released from the tetrad. The production of proorbicules, orbicules and peritapetal membrane, and the construction of a complex sporoderm with numerous apertural sites were observed. When microspore and pollen protoplasts underwent necrosis, probably as a result of temperature and osmotic stress, sporoderm layers formed around microspores, and the cell tapetum did not disintegrate. However, woody wall layers did not accumulate in endothecium cells.
Development of microspores and pollen grains of Cucumis sativus L. was studied at the light microscope level from meiosis to mature pollen. The first pollen mitosis occurs after microspore release from the tetrad at the vacuolate microspore stage, but this stage of development is not correlated with enlargement of the entire pollen grain; pollen grain volume grows continuously from microspore release until pollen dehydration, simultaneously with an increase in the amount of cytoplasm in the vegetative cell. Starch grains in the vegetative cell appear after displacement of the generative cell inside the pollen grain and disappear in the final stage of pollen maturation. Mature pollen grains are bicellular at anthesis.
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