Histology: Epidermal tissues

Prepared for B.Sc. First year Students based on the syllabus of Dr. Babasaheb Ambedkar Marathwada University.

1. B.Sc. I yeae-Semester-II
Paper-V
Histology: Epidermal Tissues
Dr. A.S. Naik,
Head,Dept.ofBotany
SBES College of Science.

2. •Histology
Part: II
Epidermal Tissues

3. TRICHOMES AND STOMATA
•The cells of epidermis are parenchymatous having protoplasm and nucleus
without intercellular spaces.
•In some plants, epidermal cells form uni/multicellular hair/trichomes.
•Trichome-Protection against water loss, other biotic facters.
•Epidermis possesses numerous minute openings called stomata.
•Main function of stomata is exchange of gases between the internal tissues
and the external atmosphere.
•Cuticle is present on the outer wall of epidermis to check evaporation of
water.
•Epidermis forms a Protective layer in leaves, young roots, stem, flower, fruits
etc.

4. Trichomes
§Trichomes from Greek(trichōma)
meaning "hair, are fine outgrowths
or appendages onplants.
§They are of diverse structure and function. Examples are hairs,
glandular hairs, scales, and
papillae.
§A covering of any kind of hair on a
plant is anindumentum, and the
surface bearing them is said to
bepubescent.
§Taxonomic character.

5. Morphology
§Some of the epidermal cells of
most plants grow out in the form of
hairs or trichomes. They may be
found singly or less frequently in
groups.
§They may be unicellular or
multicellular and occur in various
forms.
§They vary from small protuberances
of the epidermal cells to complex
branched or stellate multicellular
structures.

6. Droseracanepis-carnivorous
trichomesCanabisTrichomes Rich In Canabinoids

8. Functions of trichomes
1.Generally a dense covering of woolly trichomes controls the
rate of transpiration.
2. They also reduce the heating effect of sunlight.
3. They aid in the protection of plant body from outer injurious
agencies/herbivores/pathogens.

9. ii) Stomata.

10. StomatalApparatus

11. Structure of Stomata

13. Types of stomata
a.Anomocytic
b.Anisocytic
c.Paracytic
d.Diacytic

14. Anisocytic/Cruciferous
§i. Stoma remains surrounded by
three subsidiary cells.
§ii.Of the three subsidiary cells,
one is distinctly-smaller than the
other two.
§iii. This type of stomata is also
called unequal-celled type or Cruciferous type.
§This types of stomata are seen
commonly in genera such as
Brassica, Sedum etc.

15. Anomocytic/Ranunculous
§No subsidiary cells are
present.
§Stoma remains surrounded by
several irregularly arranged
ordinary epidermal cells.
§This type is also called
Ranunculaceoustype or
irregular-celled type.
§This type of stomata are found
commonly in several
dicotyledons, including Tridax,
Citrullus, Ranunulus, etc

16. Diacytic/Caryophyllaceous
§Stoma remains surrounded by a
pair of subsidiary cells.
§Common walls of subsidiary cells
remain at right angles to the long axis of the guard cells.
§This type is also called cross-celled
type or Caryophyilaceoustype.
§This type of stomata are commonly
seen in Ocimum, Caryophyllaceae
(e.g., Diantbus), etc.

17. Paracytic/Rubiaceous
§One or more subsidiary cells are
present.
§Subsidiary cells flank the stoma
parallel with the long axis of the
guard cells.
§This type of stomata are also
called parallel-ceiled type or Rubiaceoustype.
§This type is commonly seen in
members of Rubiaceae, and
genera such as Vigna, etc.

18. Grass type of stomata/Gramineous:
•The gramineous stoma
possesses guard cells of
which the middle
portions are much
narrower than the ends
so that the cells appear
in surface view like
dumb-bells.
•They are commonly
found in Gramineaeand
Cyperaceaeof
monocotyledons.

19. Functions of Stomata
§Two main functions:
§Transpiration
§Gaseous exchange: For i)
Respiration and
ii) photosynthesis

20. 1. Gaseous exchange

21. Transpiration