Steman,Microsporogenesis and development in Anther

                            Structure of A steman

Structure of a Steman :- 

                                                         In a typical Steman has two part,the long and selender stalk called Filament ,and the terminal bilobed Anther.

The Proximal End of the filament attach to the Thalamus part of the flower..The Size of steman is Vary from species to species.

A typical Angiosperms anther is biolobed and each lobe has two theca .Often longitudnal grooves seperates the theca.The anther is four-sided structure of four microsporangia present in  corner.

Structure of a typical steman

The microsporangia develops further in to Pollen sacs .

Hypodermal Cells of microsporangium called Archesporial Cell and Periclinical division and forms paritial cell and sporogenous cell.

Structure of Microsporangium :-

                                                                In transverse section a typical microsporangium appears near circular in outline . By the division of Parietal cell develope –epidermis,endothecium,middle layer and Tapetum.

Tapetum provides nourishment but three function as protector.

When the anther is young ,a group of compactly arranged sporogenous tissues occupies the center of each lobe.

The Sporogenous cell Function as Microspore mother cell and by the process of meiosis it will forms microspore tetrad haploid in nature.

Types of Sporogenous tissue :- 

The Microspore mother cell become rounded and undergo meiosis to form four microspore tetrad which later separate to forms pollen grain .

This process is called Microsporogenesis .

Successive  Type :- 

                                  The Wall formation takes place after the first and second division .mostly occur in monocot.

Simultaneous type :-

                                      In this type no wall is formed during first meiotic division only phrgmoplast may be formed the wall is formed after second meiotic division.Mainly in dicots.

Structure of Pollen grain :-

             It is unicellular and haploid with single nucleus.

         It has large vacoule and other cytoplasmic organelle .

             It has two layers :- Intine and Exine .

Structure of pollen grain

        The surface is spiny ,rough and furrow due to presence of Exine layer

             Exine has two parts :- sexine and nexine ,Sexine connects with nexine by the help of baculum if the baculum combine it will forms tenticular exine .

             Plasmodial tapetum helps in the deposition of sporopollenin around the Exine .

        Exine is Covered by sticy ,viscous and  sticky substance called Pollen Kit .

         In Pollen grain two mitotic division occur In first division  one generative cell and vegetative/tube cell forms and callose forms between generative cell and intine .

             During maturity callose separate and generative cell lay in the cytoplasm of vegetative cell.

        It has large vacoule and other cytoplasmic organelle .

        It has Two Layers :- Intine and Exine .

        The surface is spiny ,rough and furrow due to presence of Exine layer

         Exine has two parts :- sexine and nexine ,Sexine connects with nexine by the help of baculum if the baculum combine it will forms tenticular exine .

Structure of Exine

              Plasmodial tapetum helps in the deposition of sporopollenin around the Exine .

          Exine is Covered by sticy ,viscous and  sticky substance called Pollen Kit .

         In Pollen grain two mitotic division occur In first division  one generative cell and vegetative/tube cell forms and callose forms between generative cell and intine 

              During maturity callose separate and generative cell lay in the cytoplasm of vegetative cell.