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Microsporogensis

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arunsaini68

This document describes the structure and development of the anther and pollen grain. It contains the following key points: 1. The anther has four microsporangia surrounded by four layers - epidermis, endothecium, middle layers, and tapetum. The tapetum nourishes developing pollen grains. 2. Microsporogenesis occurs as microspore mother cells in the sporogenous tissue undergo meiosis to form microspore tetrads. 3. Mature pollen grains contain a vegetative cell and generative cell. The generative cell can divide to form two sperm cells ready for fertilization.

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Prepared by ¨CARUN SAINI Bsc (2nd ) medical Rollno. -136910054 Submitted to- Dr. Deepika .
Parts Of Flower
T.S. OF Anther
Structure Of Anther (Microsporangium) ?Bilobed and dithecus. ?A longitudinal groove separate the theca. ?In a cross- section anther is a tetragonal structure, consisting of 4 microsporangia, two in each lobes. ?Later two microsporangia of each lobe fuse as a pollen sac.
Structure Of Anther ?A microsporangium is circular and surrounded by 4 layers. ?These layers are - - Epidermis, - Endothecium, - Middle layers - Tapetum. ?Outermost layers protect the pollen and help in dehiscence of anther to release pollen.
Microsporogensis
ANTHER WALL ?Epidermis ¨C it is outermost layer of anther which is single cell in thickness - The cells of thin layer divide only anticlinicaly in order to cope up with the growing anther ?Endothecium- next to epidermis is endothecium - The cell of endothecium are radially elongated and develop cellulosic fibrous band in their inner and tangential walls
?Middle layers- next to endothecium are 1-3 middle layers. - All of them degenerate at the time of meiosis in microspore mother cell ?Tapetum- it is the innermost layer of anther wall - It is composed of single layer of cell characters by dense protoplasm and prominent nuclei - Depending upon behavior tapetum is of 2 type 1. Amoeboid tapetum- it is of primitive type. later during the drying up process of anther, periplasmodium hydrates and deposits as tryphine on the wall of pollen grain. 2.Secretory tapetum-secretory tapetal cell remain attached to middle layer till the development of pollen grains . It is more common among angiosperm
Microsporogensis
Function of tapetum ?It provide nourishment to the developing pollen grain ?it help in the formation of exine ?It hepls in the transport of food material to inside of the anther ?Tapetum helps in the formation of pollen wall
Sporogenous tissue ?Primary sporogenous tissue give rise to microspore mother cell ?Some of sporogenous cell remain non functional and serve as the food material for the developing microspore ?MMC under goes meiosis to form microspore tetrad which seprate out to form microspore or pollen grain ?The process of formation of microspore from MMC is called microsporogensis
Microsporogenesis ?The process of formation of microspores from a pollen mother cell through meiosis is called microsporogenesis. ?The cells of sporogenous tissue undergo meiosis to form microspore tetrad arranged in a cluster of 4 cells.. ?As each cell of sporogenous tissue has potential to form tetrad, so each cell is a microspore mother cell (PMC). ?On maturation and dehydration of anther, the spores dissociate and develop into pollen grains. ?Pollen grains release with the dehiscence of anther.
Microsporogensis
Pollen Grain (Male Gametophyte) ?Spherical in shape. ?Have two layered wall- outer hard exine layer and inner thin intine. ?Exine- made up of sporopolenin. Resistant to organic matter, withstand high temperature, acids, alkalis and enzymes. It has prominent apertures called germ pores, where sporopolenin is absent. ?Intine- It is thin, continuous layer, made of cellulose and pectin.
Pollen Grain (Male Gametophyte) ?Pollen grain cytoplasm is surrounded by plasma membrane. ?Mature pollen grain has 2 cells- (i) vegetative cell (ii) generative cell. ?Vegetative cell- bigger, abundant food reserve, large irregular nucleus. ?Generative cell- small, spindle shaped with dense cytoplasm and a nucleus, floats in vegetative cell cytoplasm. ?In 60% species pollen grains are shed in 2 celled stage where as 40% species shed in 3 celled stage in which generative cell divides mitotically into 2 male gametes.
Microsporogensis
Microsporogensis
Microsporogensis

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Microsporogensis

  • 1. Prepared by ¨CARUN SAINI Bsc (2nd ) medical Rollno. -136910054 Submitted to- Dr. Deepika .
  • 4. Structure Of Anther (Microsporangium) ?Bilobed and dithecus. ?A longitudinal groove separate the theca. ?In a cross- section anther is a tetragonal structure, consisting of 4 microsporangia, two in each lobes. ?Later two microsporangia of each lobe fuse as a pollen sac.
  • 5. Structure Of Anther ?A microsporangium is circular and surrounded by 4 layers. ?These layers are - - Epidermis, - Endothecium, - Middle layers - Tapetum. ?Outermost layers protect the pollen and help in dehiscence of anther to release pollen.
  • 7. ANTHER WALL ?Epidermis ¨C it is outermost layer of anther which is single cell in thickness - The cells of thin layer divide only anticlinicaly in order to cope up with the growing anther ?Endothecium- next to epidermis is endothecium - The cell of endothecium are radially elongated and develop cellulosic fibrous band in their inner and tangential walls
  • 8. ?Middle layers- next to endothecium are 1-3 middle layers. - All of them degenerate at the time of meiosis in microspore mother cell ?Tapetum- it is the innermost layer of anther wall - It is composed of single layer of cell characters by dense protoplasm and prominent nuclei - Depending upon behavior tapetum is of 2 type 1. Amoeboid tapetum- it is of primitive type. later during the drying up process of anther, periplasmodium hydrates and deposits as tryphine on the wall of pollen grain. 2.Secretory tapetum-secretory tapetal cell remain attached to middle layer till the development of pollen grains . It is more common among angiosperm
  • 10. Function of tapetum ?It provide nourishment to the developing pollen grain ?it help in the formation of exine ?It hepls in the transport of food material to inside of the anther ?Tapetum helps in the formation of pollen wall
  • 11. Sporogenous tissue ?Primary sporogenous tissue give rise to microspore mother cell ?Some of sporogenous cell remain non functional and serve as the food material for the developing microspore ?MMC under goes meiosis to form microspore tetrad which seprate out to form microspore or pollen grain ?The process of formation of microspore from MMC is called microsporogensis
  • 12. Microsporogenesis ?The process of formation of microspores from a pollen mother cell through meiosis is called microsporogenesis. ?The cells of sporogenous tissue undergo meiosis to form microspore tetrad arranged in a cluster of 4 cells.. ?As each cell of sporogenous tissue has potential to form tetrad, so each cell is a microspore mother cell (PMC). ?On maturation and dehydration of anther, the spores dissociate and develop into pollen grains. ?Pollen grains release with the dehiscence of anther.
  • 14. Pollen Grain (Male Gametophyte) ?Spherical in shape. ?Have two layered wall- outer hard exine layer and inner thin intine. ?Exine- made up of sporopolenin. Resistant to organic matter, withstand high temperature, acids, alkalis and enzymes. It has prominent apertures called germ pores, where sporopolenin is absent. ?Intine- It is thin, continuous layer, made of cellulose and pectin.
  • 15. Pollen Grain (Male Gametophyte) ?Pollen grain cytoplasm is surrounded by plasma membrane. ?Mature pollen grain has 2 cells- (i) vegetative cell (ii) generative cell. ?Vegetative cell- bigger, abundant food reserve, large irregular nucleus. ?Generative cell- small, spindle shaped with dense cytoplasm and a nucleus, floats in vegetative cell cytoplasm. ?In 60% species pollen grains are shed in 2 celled stage where as 40% species shed in 3 celled stage in which generative cell divides mitotically into 2 male gametes.