Ecological Adaltation

1. 2024-25
Ecological Assignment
Vinita
M.Sc Botany (3rd
Sem.)
232455004
Ecological
Adaptations
Name:-
Class:-
Roll No.:-
Topic:-
Submitted to:- Dr. Rajkumar Sir

2. Ecological adaptation
“The changes in the characters, which enable the organisms to withstand
the changes in the surrounding environment and to make use of these
changes for the maximum benefits, are known as adaptations.” Adaptations
in an organism or in the community are generally for the changes in the entire
environment. The organisms adapt to the changes in the surrounding atmosphere
because of the basic property of the protoplasm, known as the adaptability. The
adaptability helps the organisms to remain in the process of evolution. The
ecological adaptations are the responses shown by the plants to the
environmental conditions and they are the adjustments as per environmental
changes.
The adaptations which are induced by water factor or availability of water in
the environment are of three types – xeric, hydric and mesic. These terms
are used for the environmental conditions which are responsible for
respective adaptations.
All adaptations may be structural, physiological or behavioral, are the result
of evolution, which is a change in a species over thousands of years or within a
few lifetimes. The life cycle of any organism is controlled by number
of environmental factors. Water is the most essential factor for every
living organism. Plants growing under different environmental conditions
exhibit various adaptation. For the first time, Warming (1895) had realized the
impact

3. of different factors upon the vegetation in ecology and he classified plants on
the basis of nature of substratum on which they grow. Later on, Warming (1909)
classified the plants on the basis of their water requirements.
The plants are divided into three major groups as per their water requirements-
1.Hydrophytes- Plants growing in abundant water
i.e., in maximum water supply and near the water.
2.Xerophytes- Plants growing in dry, arid region
which shows shortage of water in the soil i.e., in minimum supply of
water.
3. Mesophytes- Plants growing in habitat with neither less nor more
water
is available i.e., moderate water supply is required.
Hydric adaptation
Plants are either growing on land or in water. The land plants get essential water
from the soil but the aquatic plants are growing within or near the water. On the
basis of availability of water, the adaptations are of three types – Xeric, Hydric and
Mesic.
A. Hydric Adaptations:
1. Water availability is far more than the requirement of plants.
2. There is no need of mechanical strengthening as plants are supported by water

4. 3. Aquatic plants can only grow partially or completely in water or in soil that is
permanently saturated with water.
4. The habitat of aquatic plants is either fresh water or marine.
5. Underwater leaves and stems are flexible to move with water currents.
As the plants are growing in hydric conditions these are known as hydrophytes
(Hydro- water, phytes - plants). There are three different types of hydrophytes -
a.Submerged hydrophytes- Plants are growing under the water surface
e.g., Hydrilla, Potamogeton, Utricularia

5. b. Floating hydrophytes – These are of two types
1.Free floating hydrophytes: Freely floats on the water surface, not rooted in the soil
e.g., Eichhornia, Pistia.
2. Floating but rooted hydrophytes: Plants are rooted in the soil but leaves
are floating on the surface of water e.g. Nymphaea, Marsilea.

6. c. Amphibious hydrophytes – These are growing in shallow water or in
muddy soil i.e., in marshy places e.g. Cyperus, Typha

7. All these hydrophytes have certain morphological, anatomical and
physiological modifications
while growing in above aquatic conditions. These modifications are
known as hydrophytic adaptations which are discussed below-

8. Morphological (External) adaptations of Hydrophytes:
Roots: Root system of hydrophytes is not of much importance, because they grow
partially or completely in water.
Roots are poorly developed (e.g., Hydrilla, Vallisneria.), reduced or completely
absent (e.g., Utricularia, Ceratophyllum,).
However, some hydrophytes have well developed adventitious roots
(e.g.,
Eichhornia, Pistia).
Root caps usually absent. Root hairs are poorly developed in most
hydrophytes.
Root tips are often provided with root pockets (e.g., Eichhornia).
Stem: In submerged hydrophytes, the stem is long, slender thin, spongy and
flexible e.g., Hydrilla.
In free floating hydrophytes, the stem or stolon is horizontal, spongy, thick and
short, floating on the surface of water e.g., Eichhornia, Azolla, Pistia
While in rooted hydrophytes like Nymphaea, Nelumbium, Cyperus, the stem is

9. a rhizome. These rhizomes live for many years and produce leaves every year.
Mucilaginous or waxy coating is present on entire plant body.
Petioles:
Some floating hydrophytes show special features in the petioles.
In free floating but rooted hydrophytes like Nymphaea and Nelumbium, petioles
are long, slender and spongy.
while they are swollen, spongy in free floating hydrophyte like Eichhornia, helps
in floating.
Leaves:
The leaves are thin, long or ribbon like (e.g., Vallisnaria).
linear
Potamogaton) or finally dissected (e.g., Ceratophyllum).
The leaves may be long, flat, and entire as in Nelumbo, Nymphaea.

(e.g.,

10. Heterophylly is observed in some plants.
Generally, the leaves are reduced in thickness and covered by waxy coating.
Anatomical (Internal) adaptations of Hydrophytes:
Root:
Cuticle is very thin or absent.
Root hairs present in amphibious hydrophytes.
Epidermis is single layered made up of thin- walled cells. Parenchymatous cortex
i.e., arenchyma is well developed. It has numerous air chambers which help
in buoyancy (floating) and rapid gaseous exchange.
Conducting tissues, i.e., xylem and phloem,
Developed poorly and less differentiated. Only xylem tracheids are present in
submerged forms while phloem is well differentiated in amphibious hydrophytes.
Mechanical tissues are generally absent. Pith is absent.

11. Leaves:
Cuticle is absent or poorly developed in Nymphaea leaves.
Epidermis is single layered with thin walled parenchymatous cells.
Chlorophyll found in all the tissues. Epidermal cells of leaves contain abundant
chloroplasts and they can function as photosynthetic tissue, especially where the
leaves and stems are very thin e.g., Hydrilla.
Stomata are totally absent in submerged plants, but in floating leaves,
stomata are present on the upper surface. In amphibious plants stomata may
be
scattered on all the aerial parts.
In submerged plants, mesophyll tissues are not differentiated while in
Other forms of hydrophytes these are well differentiated into
spongy
parenchyma and palisade tissues. They show air cavities.
In submerged leaves, air chambers are filled with respiratory and other
gases.
Mucilage canals and mucilage cells are present which secrete mucilage to protect

12. Stem:
Cuticle is very thin, poorly developed or absent.
Epidermis is single layered with thin walled parenchymatous cells.
The rhizome of Nymphaea and stem of Typha shows well developed epidermis.
Infloating forms, thin walled parenchymatous or collenchymatous
hypodermis is present which is containing chloroplasts.
Parenchymatous cortex is well developed with number of air chambers which
help in buoyancy (floating) and rapid gaseous exchange.
Endodermis and pericycle is generally distinct.
The vascular tissues, i.e., xylem and phloem, developed poorly, thin
walled except in amphibious hydrophytes.
Mechanical tissues are poorly developed or absent.

13. Physiological Adaptations of Hydrophytes:
 Osmotic concentrations of cell sap are low.
 Entire plant surface absorbs water and nutrients.
 Hydrophytes maintain active photosynthesis as chloroplasts are
distributed throughout the plant body.

14.  CO2 and O2 evolved during respiration and photosynthesis is stored in air
chambers for future use.
 No transpiration from submerged plants.
Xeric adaptation
1. Water availability in the soil is very low than the requirement of plants.
2. The temperature is very high so humidity is less which results in the
loss of water.
3. Arid, dry area with low rainfall,
4. Hot, dry climate is responsible for increasing evaporation and transpiration.
5. All these environmental conditions are responsible for drought in that
habitat

15. As the plants are growing in xeric conditions these are known as xerophytes. There
are three different types of xerophytes -
a. Drought escaping plants (Ephemerals) - These are also called as drought
evaders which have a very short life cycle i.e., they are annuals, to avoid the
drought e.g. Tribulus terrestris, Argemone mexicana, Cassia tora etc.
b.Drought tolerant/enduring plants (succulents) - They store large amount of
water in different organs of their body, so they become fleshy. They are called
succulents. The stem succulents store water in stem so it becomes fleshy, green
and photosynthetic leaves are reduced to spines e. g. Opuntia. In leaf succulents
store water in leaves and they become thick fleshy as in Aloe, Portulaca.

16. c. Drought resisting plants (Non- succulents) – These plants are the true
xerophytes. They resist the drought by showing external and internal adaptations
to dry conditions. Examples are Calotropis, Casuarina, Nerium, Acacia.

17. Morphological adaptations of xerophytes:
Root:
Root system is well developed and profusely branched.
The roots of perennial xerophytes grow deep into the ground that can
penetrate several meters down where plenty of water is available.
Most of the desert plants like Cacti develop superficial and shallow root
system which is able to absorb water that is available near the surface of the
earth.

18. Stem:
The stem is hard, woody either aerial or subterranean, sometimes covered
with wax e.g., Equisetum.
Stem may be covered with dense hairs as in Calotropis or thorns. In some
succulents, it is bulbous and fleshy.
The extreme xerophytes like Opuntia, stem is modified into leaf like, flattened
fleshy structure known as phylloclade while in Asparagus it is modified into
small needle-like green structures exactly looking like leaves called as cladodes.
Both phylloclade and cladodes perform the function of leaf i.e., photosynthesis.

19. Leaves:
• Leaves are thick and leathery, tough, shining (Nerium) or may be thick, fleshy
& succulent (Aloe).
• In some plants like Cacti, leaves are reduced, usually small and fall off during
prolonged dry conditions to prevent water loss by simply losing their leaves,
absent or modified into spines (Zizyphus, Capparis, Acacia).
• Leaf lamina may be long, narrow needle like as in Pinus or divided into many
leaflets like Acacia, leaf apex & margin is spiny (Aloe).
• Curled leaves are present in some extreme xerophytic grasses. The rolling or
folding of leaves minimizing the evaporation and water loss.

20. a) Succulent Xerophyte- Alo
b) Non succulent xerophyte-
Ziziphus

21. Anatomical adaptations of xerophytes:
Roots:
• Root cap is present. Root hairs are large in number.
• Conducting tissues, i.e., xylem and phloem, developed very well.
• Thick cuticle is present which protects internal tissues from dry and hot
soils.
Stem:
• Epidermis is thick walled and lignified.
• Some plants show wax deposition on the surface of epidermis and even in
the hypodermis.
• In succulent stems, thin walled parenchymatous cells store excess amount
of water, mucilage, latex, etc. called water storage tissues.
• Woody xerophytes produce very well-developed cork in the stem.
• Mechanical tissues and vascular tissues are well developed.

22. Leaves:
• Epidermis with thick cuticle & epidermal cells are thick walled.
• Multilayered epidermis is present on both upper and lower surface of leaves.
• Sunken stomata are present and stomatal opening is covered with number of
hairs, presence of many layered palisade tissue.
• Mesophyll is very compact with reduced intercellular spaces.
• In succulent leaves, spongy parenchyma i.e., water storage tissue stores
water.
• Thick-walled sclerenchyma cells are seen in the
hypodermis e.g., Pinus needle.
• Well-developed vascular and mechanical tissues are present.

23. Physiological Adaptations of
Xerophytes:

24.  The stomata of these plants open during night hours and remain closed
during the day to prevent water loss by reducing evaporation rate.
 The xerophytes have very high osmotic pressure of the cell sap, which
increases the turgidity of the cell sap.
 These plants control the excessive loss of water during transpiration
by reducing total transpiring surface,
 Xerophytes have greater potentiality to resist wilting.
 The protoplasm in these plants is less viscous and more permeable and resistant
to heat.
 These plants may secrete resins and waxes (epicuticular wax) on their surfaces,
which reduce evaporation.

25. THANK YOU