ASKARI

CHAPTER 2 SEXUAL REPRODUCTION IN FLOWERING PLANTS  Microsporogenesis : As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to  form microspore tetrads. As each cell of the sporogenous tissue is capable of giving rise to a microspore tetrad. Each one is a potential pollen or microspore mother cell.  • The process of formation of microspores from a pollen mother cell (PMC) through meiosis is called microsporogenesis. The microspores, as they are formed, are arranged in a cluster of four cells - the microspore tetrad.  • As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. • Inside each microsporangium several thousands of microspores or pollen grains are formed that are released with the dehiscence of anther. Pollen grain : The pollen grains represent the male gametophytes. Pollen grains are generally spherical measuring about 25-50 micrometers in diameter. It has a prominent t...

CHAPTER 2 SEXUAL REPRODUCTION IN FLOWERING PLANTS    》All flowering plants show sexual reproduction. 2.1 FLOWER - A FASCINATING ORGAN OF ANGIOSPERM   • Flowers are a morphological and embryological marvels and the sites of sexual reproduction.  2.2 PRE - FERTILIZATION: STRUCTURES AND EVENTS   • In the flower the male and female reproductive structures, the androcecium and the gynoecium differentiate and develop. You would recollect that the androecium consist of a whorl of stamens representing the male reproductive organ and the gynoocium represents the female reproductive ongan . 2.2.1 Stamen, Microsporangium and Pollen Grain  • A shows the two parts of a typical stamen - the long and slender stalk called the filament, and the  terminal generally bilobed structure called the anther. The proximal end of filament is attached to the thalamus or the petal of the flower. The number and length of stamens are variable in flowers of different species. • A t...