microsporogenisis is the formation of microspore inside the microsporangia

1. VIMAL PRIYA SUBRAMANIAN
1ST MSC BOTANY
MICROSPOROGENESIS

2. 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”

4.  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.

5. TRANSVERSE SECTION OF
MATURE ANTER

6.  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.

8.  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

9. DIVISION INSIDE THE
MICROSPORANGIA

10.  The spore mother cell undergoes meiotic division
and gives rise to 4 microspores arranged
tetrahedrally

12. 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

13.  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

14. DIFFERENT SHAPES OF POLLEN
GRAINS

15.  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

16. UNITED POLEN GRAINS

17. 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

18.  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

19. DEVELOPMENT OF MALE
GAMETES

20.  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

21. OVER ALL VIEW

22. THANKING YOU