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Department of Botany. Bharathiyar Arts and Sciemce College for Women Salem, profile picture
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Microsporogenisis

This document summarizes the process of microsporogenesis. It begins with a microsporocyte or pollen mother cell inside the microsporangia undergoing meiosis to form four haploid microspores. The microspores then develop into pollen grains with one nucleus each. Inside the pollen grain, the nucleus divides unequally forming a generative cell and tube cell. The generative cell further divides to form the male gametes while the tube cell forms the pollen tube. Overall, microsporogenesis involves meiosis within the anther to produce haploid microspores that develop into pollen grains containing the male gametophyte.

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VIMAL PRIYA SUBRAMANIAN 1ST MSC BOTANY MICROSPOROGENESIS
MICROSPOROGENISIS  The formation of microspores inside the microsporangia or pollen sac of seed plants.  A diploid cell in the microsporangium, called a microsporocyte or a pollen mother cell, undergoes meiosis and gives rise to four haploid microspores”
 The microsporangia are developed inside the corners of the 4-lobed anther.  Young anther are more or less oblong in shape in section and made up of homogeneous mass of meristematic cells without intercellular space with further development, the anther becomes 4-lobed. The outer layer of anther is called epidermis.
TRANSVERSE SECTION OF MATURE ANTER
 Bellow the epidermis, at each corner, some cells become differentiated from others by their dense protoplasm archesporium or archesporial cells.  Each archesporial cell prymary parietal cell then divides mitotically and primary parietal cell layer at eachcorner.  Bellow the parietal cell layer, the primary sporogenous cell remain in groups the sporogenous tissue.
 The cells of primary parietal layer then divide both periclinally and anticlinally and form multilayered antheridial wall.  The innermost layer of antheridial wall, which remains in close contact with the sporogenous tissue, function as nutritive layer, called tapetum.  The primary sporogenous cells either directly function as spore mother cells or divide mitotically into a number of cells which function as spore mother cells
DIVISION INSIDE THE MICROSPORANGIA
 The spore mother cell undergoes meiotic division and gives rise to 4 microspores arranged tetrahedrally
STRUCTURE OF POLLENGRAINS (MICROSPORE) Pollen grains is the 1st cell of the male gametophytes  Which contain one haploid nucleus.  These are various shapes  polyhydral  cubical  trigonal  cylindrical
 The size of pollen grains generally varies from 10- 80Mm, but the size may even 100Mm in diameter.  The pollen grains have a 2 walls outer exine further divide into two # sexine # nexine # intine
DIFFERENT SHAPES OF POLLEN GRAINS
 The exine is tough and cutinised. It may be protect the pollen from external injury.  The intine is very thin , elastic and delicate.  Usually the mature pollens are not attached in tetrad and they get separated from one another.  In some plants they do not get separated from one another in orchid, asclepidaceae all the pollen grain remain sac remain united forming the polinium bag then pinaceae are provided wing like expansion
UNITED POLEN GRAINS
DEVELOPMENT OF MALE GAMETOPHYTE(MICISIROGAMETOGENES IS)  Pollen grain have a haploid nucleus  During early stage inside the microsporangium the cell under goes unequal division and forms a small  generative cell and  vegetative cell/tube cell  Initially generative cell lives corner of the spore wall within short time ,it gets detached and becomes elipsoid in shape
 And remains the suspended in the cytoplasm of vegetative cell (2 celled stage).  Later on generative cell divides and gives rise to 2 ellipsoidal or spherical cells.  The second division of generative cell may take place either in the pollen tube which develops through germ pore after polination
DEVELOPMENT OF MALE GAMETES
 The nucleus of the vegetative cell is commonly known as tube nucleus.  It usually shows sign of degeneration with the maturation of generative cell.  Finally the tube nucleus remains within spore or may be enter the pollen tube .sooner or later it may be degenarated
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