01}Reproduction in lower & higher plants part 2 sexual reproduction.

01 Reproduction in Lower and Higher Plants - part 02 - Sexual Reproduction, T. S. of Anther


Sexual Reproduction :
  • It involves fusion of two compatible gametes or sex cells. 
  • All organisms reach to the maturity in their life before they can reproduce sexually. 
  • In plants, the end of juvenile or vegetative phase marks the begining of the reproductive phase and can be seen easily in the higher plants at the time of flowering. 
  • The flower is specialized reproductive structure of a plant in which sexual reproduction takes place. 
  • The function of flower is to produce haploid gametes and to ensure that fertilization will take place. 
  • Typical flower consists of four different whorls viz. - 
  1. Calyx
  2. Corolla 
  3. Androecium and 
  4. Gynoecium. 
  • Sexual reproduction involves two major events viz. - 
  1. Meiosis and fusion of gametes to form diploid zygote and 
  2. Production of genetically dissimilar offsprings. 
  • Variations are useful from the point of view of the survival and the evolution of species, over the time.
  • Sexual reproduction is characterised by  - 
  1. fusion of the male and female gametes (fertilization)
  2. Formation of zygote and 
  3. Embryogenesis. 
  • Sequential events that occur in sexual reproduction are grouped into three distinct stages viz,
  1. Pre-fertilization
  2. Fertilization and the 
  3. Post-fertilization.
Always Remember :
  • Diploid sporophyte is the predominant plant body in all angiosperms, where meiosis takes place to produce haploid spores that form gametophyte.  
  • Gametophytes are considerably reduced and develop within the flower. 
  • They produce gametes.
  • The male reproductive whorl of flower is called androecium. 
  • Individual member of androecium, is called stamen. 
  • Stamen consists of -  
  1. Filament
  2. Connective and 
  3. Anther. 


Structure of Anther : 

  • An immature stage of anther is represented by group ofparenchymatous tissue surrounded by single layered epidermis. 
  • Anther is generally dithecous (having two lobes) and tetrasporongiate. 
  • Each monothecous anther contains two pollen sacs. 
  • In dithecous anther four pollen sacs are present. Therefore, it is tetrasporongiate. 
  • The heterogenesity (differenciation) arises when some hypodermal cells get transformed into archesporial cells.



T. S. of Anther : 

  • The archesporial cell divides into an inner sporogenous cell and outer primary parietal cell. 
  • Sporogenous cell forms sporogenous tissue. 
  • Each cell of sporogenous tissue is capable of giving rise to a microspore tetrad. 
  • Parietal cell undergoes divisions to form anther wall layers. 
  • The wall of mature anther consists of four layers. 
  1. Epidermis
  2. Endothecium
  3. Middle layer
  4. Tapetum
  • Epidermis is the outermost protective layer made up of tabular (flattened) cells. 
  • Endothecium is sub-epidermal layer made up of radially elongated cells with fibrous thickenings. 
  • Inner to endothecium is middle layer made up of thin walled cells (1-2 layered), which may disintegrate in mature anther. 
  • Tapetum is the inner most nutritive layer of anther wall. It immediately encloses the sporogenous tissue (microspore mother cells)

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