2025
|MOST COMMON QUESTIONS WITH CORRECTLY
VERIFIED ANSWERS|ALREADY A+
GRADED|GUARANTEED PASS
Androecium - (male reproductive organ) It consists of a whorl of stamens.
Stamen - Stamen = Anther (terminal bilobed structure) + Filament (long and slender
stalk).
Filament is having 2 ends - A. Distal end attached to the anther. B. Proximal end -
attached to the thalamus or the petal of the flower.
A typical angiosperm anther - A typical angiosperm anther is bilobed with four
microsporangia (located at the corners, two in each lobe). Both theca are separated by a
longitudinal groove.
Structure of microsporangium - - Each microsporangia extend along the length of an
anther and is packed with pollen grains. It appears nearly circular in transverse section. It
surrounded by 4 wall layers 3. Middle layers. 1. Epidermis (outermost). 2. Endothecium. 4.
Tapetum (innermost).
Functions of outer three wall layers - 1. Protection. 2. Dehiscence of anther to release the
pollen
Tapetal cells - Tapetal cells are usually bi-/multi-nucleated with dense cytoplasm.
Tapetum Function - These give nourishment to the developing pollen grains.
Microsporogenesis - Sporogenous tissue : It is the group of compactly arranged
homogenous cells in the centre of each micro -sporangium in a young anther Each cell of
sporogenous tissue act as Pollen mother cell (PMC/2n) ---(Meiosis / Process :
Microsporogenesis) - → Microspore tetrad -----(When anthers mature and dehydrate)----→ 4
Microspores (Each haploid (n)] are released → Each microspore develop into a pollen grain -----
(Dehiscence)----→ Thousands of pollen grains come out of anther.
, Pollen grain Shape - Generally spherical.
Pollen grain Size - 25-50 mu in diameter.
Wall of pollen grain is 2 layered - Exine Intine
Outer layer - Exine
Inner layer - Intine
Thick layer - Exine
Thin layer - Intine
Hard and discontinuous layer - Exine
Less hard and continuous layer - Intine
Made up of sporopollenin - Exine
Made up of cellulose and pectin - Intine
fascinating patterns and designs - The exine exhibits fascinating patterns and designs
It lacks such patterns and designs - Intine
role of sporopollenin - Pollen grains are preserved as fossils for very long durations
because of sporopollenin in exine.
Few features of Sporopollenin - 1. It is one of the most resistant organic material known.
2. It can resist damage from high temperature, strong acids and alkalis. 3. No enzyme is known
to degrade sporopollenin,
Germ pores - Those prominent apertures in exine of pollen grain where sporopollenin is
absent.
Structure of Pollen grain - Initially the pollen grain is one celled but when the pollen grain
matures, it acquires 2- celled stage, 1. Vegetative cell 2. Generative cell
cell Larger in size - 1. Vegetative cell
cell Small in size - 2. Generative cell
cell Generally spherical, - Vegetative cell
cell with Large irregularly shaped nucleus. - Vegetative cell