This document discusses the morphology and structure of pollen grains. It begins with an introduction to pollen grain development through microsporogenesis. Pollen grains are generally spherical and 25-50 micrometers in diameter, containing a resistant outer wall and inner cellular contents. The pollen wall consists of two layers - an outer exine layer made of sporopollenin that is highly resistant, and an inner intine layer made of cellulose and pectin. The exine layer provides sculpturing and pores for germination. Features of the pollen wall help with classification and allow pollen grains to be well-preserved as microfossils.

1. Presented by...
Thakor Maitri M.
M.Sc. (Botany)
Department of life sciences,
H.N.G.U., Patan.
❶

2. Content
❷
 Introduction
☻The pollen grains (morphology)
 Pollen Wall features

3. Introduction
❸
 In the male gametophyte, first cell
generation represent by the microspores or
the pollen grains.
 The development of male gametophyte is
remarkably uniform in angiosperms.

4.  Microsporogenesis:
Diploid cell of micro-
spore mother cell
divided by meiosis &
make 4 haploid spores
at the end of the
process (i.e., tetrad).
Each tetrad becomes
the microspore. = Male
gametophyte.
❹

5. Microspore - morphology
❺
 The pollen grains or microspores are the
male reproductive bodies of a flower, and are
contained in the pollen sac or micro
sporangium.
 They are very minute in size, and are like
particles of dust.
 It is commonly globular in outline, though
several other shapes are also found. The
diameter is mostly 25 – 50 µm.

6. ❻
 There is a highly resistant wall on the
outside and cellular contents inside.
 Pollen grain’s cytoplasm is rich in starch and
unsaturated oils, it protect the chromosomes
from radiation damage.

7.  Each pollen grain
consists of a single
microscopic cell,
possessing two
coats : a rough outer
wall of cutin called
the exine and an
inner thin wall of
cellulose and pectin
substances called
the intine.
❼

8. ❽
 According to Erdtman the external surface of
pollen is characterised by various markings
such as pilate, reticulate, striate, ornate,
crasssisexinous, tenuisexinous, subsaccate,
tegillate, etc.

9. ❾
 The exine possesses one or more thin
places known germ pores.

10. Pollen wall features
❿
 pollen wall is also known as sporoderm,
which have highly resistant on the outside of
the polllen grains.
 Normally the pollen wall possesses two layer :
the exine and the intine.
 The exine is made of highly resistant fatty
substance called sporopollenin (Zelisch, 1932).

11. ⓫
 The outer layer is not even degraded by any
physical or biological agents like high
temperature, strong acid or alkali, any
enzyme, etc. Because of the sporopollenin,
pollen grains are well preserved as
microfossils.
 At places, the exine possesses proteins for
enzymatic and compatibility reactions.

12. ⓬
 The intine is thin and mainly consist of
pectin & cellulose, so it is pecto-cellulosic in
nature.
֎ The intine can be destroyed during
acetolysis.
 At places, the intine contains enzymatic
proteins ( Knox and Heslop- Harrison,1971).

13. ⓭
 The tectum provides a characteristic
sculpturing or designs over the surface of
pollen grains, e.g., ridges, tubercles, spines,
reticulations.

14. ⓮
 In isect pollinated pollen grains the exine is
spiny as well as covered by a yellowish,
viscous sticky and oily layer called pollenkit.
 Pollenkit is made up of lipid, carotenoids
and some proteins.

15. ⓯
 At certain places the exine is thin or absent &
the areas may have thickened intine or
deposition of callose. It’s called germ pores
(if rounded) or germinal furrows (if
elongated).

16. ⓰
 Pollen grains are generally tricolpate (with
three germ pores) in dicots and monocolpate
(with single germinal furrow) in monocots.

17. References
⓱
1)A text book of Botany – Embryology of
Angiosperms.
♣ Author :Sanjay kumar singh
♣ Edition :1971 (First Edition)
2)College Botany ( Volume two ).
♣ Author : S. Sundara Rajan.
♣ Edition :2015
3) WWW.Slideshare.net

18. ⓲