The document discusses the development of microsporangium, the male reproductive structure found in flowers. It begins by introducing the basic structure of the stamen, which contains the filament, anther, and connective tissue. It then describes the development of the microsporangium wall layers and the sporogenous tissue within. Finally, it explains the process of microsporogenesis, where microspore mother cells within the anther undergo meiosis and cytokinesis to form pollen grains (microspores). The pollen grains each contain a single cell with two coat layers and will function as the male gametophyte to facilitate fertilization.

1. Microsporangium
Presented by : Salvi Pinky P.
M.sc sem - 2
Botany - 404
Department of Life Sciences ,
H. N. G. U., Patan

2.  Introduction
 Development of microsporangium
 Anther wall
 Sporogenous tissue
 Microsporogenesis
Content

3. Introduction
• Microsporophyll or the stamen is the male reproductive
part of the flower, which consists filament, anther and
connective.
• Anther is the fertile part of microsporophyll sometimes it
is sterile called staminode.
• The filament is the slender stalk of the stamen and the
anther is the expended head borne by the filament at its
tip.

4. Structure of Stamen

5. Development of microsporangium
• In each lobe a few cells in the hypodermal region become
differentiated by their large size, radial growth, dense cytoplasm
and conspicuous nuclei.
• There is much variation in the number of cells of archesporium.
• Generally, the archesporium consists of a two to three cell, wide
plate running along the entire length of the lobe.
• The extent of archesporium varies both length wise and breadth
wise.

7. The wall of microsporangium
• The epidermis along with the 3 – 5 layers derived from the
primary parietal layer form the wall of the sporangium.
• The cells of the epidermis devide anticlinally only.
• The cells thus formed become greatly stretched and flattened.
• Sometimes its cells may become greatly lignified or cutinized.
• A mature anther wall consists of 4 layers :
A) epidermis
B) endothecium
C) middle layer
D) tapetum

9. • Types of tapetum : -
1) Amoeboidal Tapetum : -
a) Sagittaria type
b) Butomus type
c) Sparaganium type
d) Triglochin type
2) Secretory or Glandular Tapetum

10. Sporogenous Tissue
• The primary sporogenous layer cells give rise to the microspore
mother cells or the pollen mother cells.
• The sporogenous cells in normal way divide several times
mitotically before functioning as pollen mother cells.
• In certain cases the primary sporogenous cells may either show
only few divisions or no divisions at cell, thus giving rise to a very
small group of sporogenous cells or the primary sporogenous cells
themselves function directly as the microspore mother cells.

11. Microsporogenesis
• The microspore mother cells which are at first polygonal and
closely packed gradually become rounded and loosely arranged in
the rapidly enlarging microsporangium.
• Each functional spore mother cell produces four microspore or
pollen grains.
• Types of microsporogenesis : -
A) Meiosis
B) Cytokinesis type : -
1) Successive type
2) Simultaneous type : -
a) Tetrahedral
b) Isobilateral tetrad
C) Decussate tetrad
d) T – shaped
e) Linear tetrad
3) The pollen grains

13. Cytokinesis type : -
• The division of the microspore mother cells may be for the
successive and simultaneous type.
• In the successive type, a cell plate is developed immediately after
the first meiotic division and another in each of the two daughter
cells after the second meiotic division.
Successive type : -
• In this type a cell wall is laid down between the two daughter
nuclei immediately after their formation during the first meiotic
division.
• The second meiotic division takes place forming two daughter
cells.
• And then again a wall is formed in if the two daughter cells.

14. Simultaneous type : -

15. • This type is commonly formed in dicotyledons plants.
• In this case the nucleus of the microspore mother cell divides
twice forming four haploid nuclei laying in the common mass of
cytoplasm of the mother cell.
• The 4 nuclei thus formed are being arranged in tetrahedral
manner and after cleavage of cytoplasm the 4 distinct segments
are formed.
The pollen grains : -
• The pollen grains or microspores are the male reproductive
bodies of a flower, and are contained in the pollen sac or
microsporangium.
• They are very minute in size, and are like particles of dust.
• Each pollen grains consists of a single microscopic cell, possessing
two coats : - 1) the exine
2) the intine

16. Structure of the pollen grains :

17. References
• A Taxt book Of botany : Angiosperms :
by : - B. P. Pandey
https://www.kullabs.com
https://en.m.wikipedia.org
https://www.pnas.org

18. THANK YOU