Xerophytes are plants which grow in xeric environment. They have adapted morphological, physiological and anatomical changes in order to survive in xeric conditions. Various anatomical adaptations in xerophytic plants which helps to absorb as much as water as possible, to store for long time and to reduce the rate of transpiration which enables them to survive in xeric condition are included in the presentation.

1. Anatomical features of
xerophytic plants
Presented by:
Megha Varshini Gowda B R

2. Contents
• Introduction
• Anatomical features in
1. Xerophytic root.
2. Xerophytic stem.
3. Xerophytic leaves.
• Conclusion
• References

3. Introduction
• Eugenius Warming (1909) classified plant communities as
hydrophytes, mesophytes and xerophytes.
• Xerophytes are plants which grow in xeric environment.
• Xerophytes are generally classified as:
• Plants growing under xeric condition become adapted
structurally and physiologically to habitats.
• Morphological adaptations includes well developed root system,
modification of stem into cladode and phylloclades, leaves are
sclerophyllous, microphyllous, trichophyllous or sometimes
caducous.
Xerophytes
Ephemerals Succulents Non-Succulents

4. Anatomical features seen in xerophytic
roots
• Presence of suberised exodermis- regulates the inverse flux of
water.
• Water storage parenchyma cells in cortical region.
Fig.1: Suberised exodermis in
Primula palinuri petagna.
Fig.2: Water storage parenchyma
in Asparagus acutifolius.

5. • Presence of additional layers of cells with thickened walls
around the stele and lignified pith in Asparagus acutifolius.
• Endodermis with thickened cell walls and additional layers of
thick walled cells around stele in Lygeum spp.
Fig.3: Additional thick walled layer of
cells and lignified pith in
Asparagus acutifolius.
Fig.4: Endodermis with thickened
cell walls in Lygeum spp.

6. Adaptation Function Example
Suberised exodermis Regulates reverse flux of
water.
Primula palinuri
Parenchyma in cortex Stores water Asparagus acutifolius
Additional layer of thick
walled cells around stele
Prevents desiccation Asparagus acutifolius
Thick walled endodermis Regulates reverse flux of
water.
Lygeum spp
Table.1: Summary of xerophytic adaptations in roots.

7. Anatomical features seen in Xerophytic
stems
Epidermis
• It is well developed with
thick walled cells.
• Thick cuticle gets deposited
on the outer surface of the
cells.
• Deposition is multilayered
in Capparis stem. The
thickness of deposition
is directly proportional
to the xeric conditions.
Fig.5: Cuticle layer.

8. Epidermal hairs
• Multicellular epidermal hairs made up of rectangular cells,
apical cell is rounded and slightly bulbous are present in
Bougainvillea stem.
• Epidermal hairs in case of Casuarina stem arises from base of
furrow and each trichome is sickle shaped consisting of 2 basal
cells and a long thick walled terminal cell.
Fig.6: Multicellular trichomes in
Bougainvillea stem
Fig.7: Trichomes arising from furrows
in Casuarina stem.

9. Hypodermis
• It is well developed and is made up of several layers of thick
walled cells
• It is composed of collenchyma cells or sclerenchyma cells.
• In Casuarina, T-shaped
sclerenchymatous hypodermis
is found below the ridges.
• Stomata are sunken, if present.
• Xylem and phloem are well
developed.
Fig.8: Sclerenchymatous hypodermis
below ridges of Casuarina stem.

10. • In succulent xerophytes, the ground tissue of stem is made up of
thin walled parenchyma cells.
• These cells preserve excess of water and mucilage in them and
therefore the stem is fleshy.
Fig.9: T.S of stem of Euphorbia tirucalli.

11. Modification of stem
Phylloclade
• Stem becomes flattened, grean
and leaf-like and performs
photosynthesis. Shows nodes
and internodes.
• Sunken stomata present on both
sides.
• Thick sclerenchymatous patches
–uniformly distributed above
each vascular bundle.
• Scelenchymatous patches are
present at the two corners.
• Well developed layers of
palisade on both sides.
Fig.10: Phylloclade of
Muehlenbeckia platyclada.
Fig.11: V.S of phylloclade of
Muehlenbeckia platyclada.

12. Cladode
• Modification of stem in which a branch of single internode is
flattened and becomes leaf-like. The proper leaf is reduced to a
scale in the axil of which develops a group of linear, narrow
structure called cladode.
• The epidermis is covered externally by a thick cuticle.
• The palisade and spongy cells contain abundant chloroplasts.
• Stomata are few in number as a check against transpiration.
Fig.12: A part of a cladode of
Asparagus asparagoides. Fig.13: Internal structure of cladode.

13. Adaptation Function Example
Thick cuticle
Protection against
desiccation
Capparis spp.
(multilayerd cuticle)
Trichomes
Maintains humid air around
stomata
Bougainvillea
Casuarina(sickle shaped)
Sclerenchymatous
hypodermis
Protects internal tissue from
high light intensity.
Casuarina spp.
Thin walled parenchyma Preserve excess of water
and mucilage
Euphorbia tirucalli
Modifications:
1.Phylloclade
Sunken stomata
Sclerenchyma surrounds vb
Reduces transpiration Muehlenbeckia platyclada.
2. Cladode
Well developed palisade
cells
Increase in photosynthetic
activity
Asparagus asparagoides
Table.2: Summary of xerophytic adaptations in stem.

14. Anatomical features seen in xerophytic
leaves
The organ that is most strikingly modified in xerophytes is the leaf.
Epidermis
• Cells are small but compactly arranged. It is single layered with
thick walls.
• Occasionally epidermis is multilayered- may be on the dorsal
surface(Ficus) or on both the surface(Nerium).
Fig.14: Additional layers of epidermis
in Nerium oleander L.

15. Bulliform cells
• Certain grass leaves have motar cells which play major role in
rolling of the leaves during the period of dryness.
• These cells are thin walled, greatly enlarged and sensitive to
turgor changes.
• When these are turgid, leaf remains flattened and when flaccid,
the lamina rolls and minimize the exposure of transpiring
surface.
Fig.15: Bulliform cells in Zea mays L.

16. Stomata
• Stomata are of sunken type.
• Reduction of transpiration is of utmost importance and it is
possible only if the stomata number per unit area is reduced or if
the stomata are elaborately modified in their structure.
• Walls of guard cells and subsidiary cells are heavily cutinised
and lignified.
• The stomatal cavities are often
provided with stomatal hairs.
• In certain desert plants, such
as Capparis spinosa and
Aristida ciliata stomata may
sometimes get blocked due to
deposition of resinous matter
or wax.
Fig.16: Sunken stomata in Yucca sp.

17. Mesophyll tissue
• Well developed and differentiated into compactly arranged
palisade tissues and loosely arranged spongy tissue.
• Palisade parenchyma is usually present towards dorsal surface
and are arranged in a single layer.
• In Nerium, Ficus and Atriplex, palisade is present on both adaxial
and abaxial surfaces and spongy tissues lie in between the
palisade layers.
Fig.17: Palisade layer in both abaxial and adaxial surface of Nerium leaf.

18. • Vascular tissues are well developed and are differentiated into
xylem with lignified elements and phloem.
• In addition to central vascular bundle in the midrib region,
there are several other vascular bundles too as seen in Nerium.
• Presence of cystolith, a deposition of calcium carbonate in
certan cells of the upper epidermis can be seen in
Ficus bengalensis leaf.
• Mechanical tissues are well developed, including several kinds
of scelreids.

19. • In certain non succulent xerophytes ( Ammophila, Agropyron)
leaves become rolled and folded in such a way that stomata
occupy the hidden position, thus minimizing the rate of
transpiration.
Fig.18: Cross section of rolled/folded
leaves of Ammophila arenaria.
Fig.19: A part enlarged.

20. Modification of leaves
Phyllode
• Petiole gets modified to form a flattened and leaf-like structure in
Acacia auriculiformis.
• Epidermis is covered by thick cuticle, partially sunken stomata
are present in lower epidermis.
• Palisade is well developed and present on both surface.
• Massive sclerenchyma surrounds the bigger central bundle and
form a cap-like structure over the smaller corner bundles.
Fig.21: T.S of phyllode of
Acacia auriculiformis.Fig.20: Phyllode of Acacia auriculiformis.

21. Adaptation Function Example
Multilayered epidermis
with thick cuticle
Reduces transpiration rate Ficus(dorsal surface)
Nerium oleander L.(both
the surface)
Bulliform cells Rolling of leaves to
minimize exposure of
transpiring surface.
Zea mays L
Sunken stomata Reduction of water loss
during transpiration
Capparis spinosa
Well developed palisade
cells
Minimise direct penetration
of light
Ficus, Atriplex
Several vascular bundles Nerium oleander L.
Rolled/folded leaves Maintain humid air around
stomata
Ammophila arenaria
Modification- Phyllode
Sunken stomata
Reduces transpiration
Maintain humid air around
stomata
Acacia auriculiformis
Table.3: Summary of xerophytic adaptations in leaves.

22. Conclusion
• Plants which are adapted to grow in scarcity of water are
called as xerophytes.
• They have adapted morphological, physiological and
anatomical changes in order to survive in xeric conditions
• They develop certain anatomical adaptations to absorb as
much as water as possible and to retain it in their organs for
long time and to reduce the rate of transpiration which enables
them to survive in xeric condition.

23. References
• Pandey, S.N and Chadha, A.1996. Plant anatomy and
embryology. Vikas Publications, New Delhi.
• Shukla, R.S and chandel, P.S.2000. Plant ecology and soil
science. S Chand Pub.
• Subrahmanyam, N.S and Sambumurty
A.V.S.S.2006.Ecology.2nd ed.Rastogi Pub.
• https://www.ncbi.nlm.gov/pmc/articles/PMC3762664/#!po=12.
1875
• https://journal.lib.uoguelph.ca/index.php/surg/aticle/view/1239/
1801
• https://www.scribd.com/mobile/doc/22240581/xerophytes-
plants-with-special-characteristics-such-thst-they-can-survive
• https://link.springer.com/chapter/10.1007/978-3-642-32653-0_2