ECOLOGICAL ADAPTATIONS

• PLANT ADAPTATION
• ADAPTATIONS IN HYDROPHYTES
• ADAPTATIONS IN XEROPHYTES
• ADAPTATIONS IN HALOPHYTES
• ADAPTATIONS IN EPIPHYTES
• ADAPTATIONS IN PARASITES
PLANT ADAPTATIONS
 TYPES OF ADAPTATIONS

Structural adaptations
are the way something is built
or made.
Behavioral adaptations
are the way something acts
naturally or by instinct.
 STRUCTURAL
ADAPTATIONS
Adaptations to get food
Leaves and stems absorb energy from the sun.
 BEHAVIORAL ADAPTATIONS
Adaptations to get food
Plants lean or grow towards the sun.
Roots grow down into soil.
Vines climb up trees to catch sunlight.
 STRUCTURAL ADAPTATIONS
Adaptations to get water and nutrients
Roots soak up water and nutrients from soil.
 BEHAVIORAL ADAPTATIONS
Adaptations to get water and nutrients
Desert flowers can stay dormant for months,
only coming to life when it rains.
 STRUCTURAL ADAPTATIONS

Adaptations for reproduction

Brightly colored flowers with nectar attract
pollinators such as birds, bees and insects.
 STRUCTURAL ADAPTATIONS
Adaptations for reproduction
Sweet fruit attracts animals that spread seeds
far away.
Some seeds are shaped to catch the wind.
 BEHAVIORAL ADAPTATIONS
Adaptations for reproduction
Plants drop seeds to grow new offspring.
 STRUCTURAL ADAPTATIONS
Adaptations for defense
Spines and thorns protect plants from predators
 STRUCTURAL ADAPTATIONS
Adaptations for defense
Poison Ivy and Poison oak have toxins that
give predators a painful itchy rash.
 HYDROPHYTES
(Greek, Hudor = water and Phyton = Plant;
water plant):
Plants which grow in wet places or in water
either partly or wholly submerged are called
hydrophytes or aquatic plants.
Examples are Utricularia, Vallisneria,
Hydrilla, Chara, Nitella, Lotus,
Ceratophyllum, Trapa, Pistia, Eichhornia
(water hyacinth), Wolffia, Lemna, etc
URTICULARIA VALLISNERIA HYDRILLA
CLASSIFICATION OF
HYDROPHYTES
 SUBMERGED HYDROPHYTES
Plants which grow below the water surface
not in contact with atmosphere
may be free-floating(Urticularia) or rooted
(Vallisneria, Hydrilla)
 FLOATING HYDROPHYTES
float on the surface or slightly below the surface of water
These plants are in contact with both water and air
They may or may not be rooted in the soil
floating plants have been divided into two groups
(i) Free floating hydrophytes:
float freely on the surface of water but are not rooted in the mud
Examples - wolffia arhiza, Trapa bispinosa, Eichhornia crassipes
(ii) Floating but rooted hydrophytes:
submerged plants are rooted in muddy substrata of Ponds Rivers
Examples - Nelumbium speciosum(Lotus), Victoria regia (water lily)
 AMPHIBIOUS HYDROPHYTES
Adapted to both aquatic and terrestrial modes of life
Grow either in shallow water or on the muddy substratum
Those which grow in saline marshy places are termed as
‘halophytes’.
Roots and some parts of stems and leaves in these plants may
be submerged in water or buried in mud
Aerial parts of these amphibious plants – mesophytic/
xerophytic features
Submerged parts develop true hydrophytic characters
Some varieties of rice plants, (Oryza sativa), Marsilea,
Sagittaria, Jussiaea
shoots are completely exposed - roots are buried in water lodged
soil or mud - marsh plants
Cyperus, Typha
 AMPHIBIOUS HYDROPHYTES
MARSILEA SAGITARRIA

JUSSIAEA JUSSIAEA
 HYDROPHYTIC ADAPTATIONS
Morphological Adaptations
Roots:

Utricularia, Slavinia - roots are absent.

In submerged plants - Vallisneria roots are poorly developed.
floating plants - Pistia, in place of root caps, root pockets are found.
Root hairs are poorly developed in hydrophytes.

Stems:
Stems are spongy, flexible, slender and long in submerged
hydrophytes like Hydrilla.
In floating plants like Pistia, Azolla the stems are horizontal, spongy
and floating.
In hydrophytes which bear roots as in Cyperus, Potamogeton the
stem is a rhizome or stolon.
 Morphological Adaptations
Pistia Azolla

Cyperus Potamogeton
 Morphological Adaptations
Petioles:

Petioles of submerged plants, with free floating leaves are long,

spongy and slender. Example: Nymphaea and Nelumbium.
In free floating plants like hydrophyte the petiole is swollen and
helps in floating. Example: Eichhorina.

Leaves:
Utricularia - leaves are finely dissected
Vallisneria - the leaves are long and narrow.
In both, the adaptation is to offer little resistance to water current.
The leaves of free floating hydrophytes are smooth and shining and
coated with wax.
The wax prevents water from clogging and also protects the leaf
from physical and chemical injuries.
 Morphological Adaptations
Nymphaea Nelumbium
 Anatomical Adaptations
The anatomical modifications
1. Reduction in protecting structures,
2. Increase in the aeration,
3. Reduction of supporting
mechanical tissues, and
4. Reduction of vascular tissues.
1. REDUCTION IN PROTECTING STRUCTURES
Cuticle is totally absent - submerged parts
present in the form of very fine film - exposed to atmosphere.
Epidermis - not a protecting layer ,absorbs water, minerals and gases
Epidermal cells - chloroplasts, thus they can function as
photosynthetic tissue, thin leaves & stem - HYDRILLA
Hypodermis in hydrophytes is poorly developed.
Its cells are extremely thin walled.
 Anatomical Adaptations
2. INCREASE IN THE AERATION
Stomata – absent- submerged parts of the plants
exceptional cases, vestigial and functionless stomata
In the floating leaves - stomata develop in very limited number –
only UE
In amphibious plants stomata - scattered on all the aerial parts
 Anatomical Adaptations
3. REDUCTION OF SUPPORTING MECHANICAL TISSUES
Submerged portions - sclerenchyma is totally absent
Special type of sclereids called asterosclereids - mechanical support.
Sclerenchyma is present in little or moderate quantities in the aerial
portions of the plant.
 Anatomical Adaptations
4. REDUCTION OF VASCULAR TISSUES.

The vascular bundles - reduced to few or even to one - located at

the center.
Xylem cells are very few.
Phloem tissues are not well developed, there are a few exceptions.
In the submerged - stomata are totally absent or vestigial.
They are present only on the upper surface
In most of the hydrophytes plant the roots, stems and leaves have
air chambers
They have CO2 and O2 gases that help them in respirations and
photosynthesis.
The air chambers also help in buoyancy and provide mechanical
support.
 Physiological Adaptations
Low osmotic concentration of cell sap.
Nutrients – plant surface – submerged plants
The gases are exchange from the water through the surface cells.
The gases produced during photosynthesis and respiration are partly
retained in the air chambers of aerenchyma to be utilized as and
when required.
There is no transpiration from the submerged hydrophytes.
However emergent plants and free floating hydrophytes have
excessive rate of transpiration.
Mucilage cells and mucilage canals secrete mucilage to protect the
plant body from decay under water.
Physiological Adaptations
 XEROPHYTES
Plants which grow in dry habitats or xeric conditions are called
xerophytes
Xeric habitats may be of following types:
1. Habitats physically dry e.g., desert, rock surface, waste land, etc
2. Habitats physiologically dry
3. Habitats dry physically as well as physiologically, e.g., slopes of
mountains.
Desert and semi-desert regions, yet they can grow in mesophytic
conditions where available water is in sufficient quantity.
These plants can withstand extreme dry conditions, low humidity
and high temperature.
 XEROPHYTES
un-favourable conditions - develop special structural
and physiological characteristics which aim mainly at
the following objectives:

(i) To absorb as much water as they can get from the

surroundings;
(ii) To retain water in their organs for very long time;
(iii) To reduce the transpiration rate to minimum; and
(iv) To check high consumption of water
 XEROPHYTES
Xerophytes are categorized into several groups according to
their drought resisting power.
1. Drought escaping plants:
These are short-lived.
During critical dry periods – survive - form of seeds and fruits
Favourable conditions (which are of very short duration),
the seeds germinate - small sized plants i life cycles - few
weeks
The seeds become mature before the dry condition approaches.
These are called ephemerals /drought evaders /drought
escapers.
Zygophyllaceae, Boraginaceae, some grasses etc.
 XEROPHYTES
2. Drought enduring plants:
These are small sized plants which have capacity to endure or
tolerate drought.
3. Drought resistant plants:
can resist extreme droughts.
Some grow on rocky soils (Lithophytes) some in deserts,
some on the sand and gravels (Psammophytes)
some may grow on the waste lands (Eremophytes).
Some plants of xeric habitat have water storing fishy organs,
some do not develop such structures.
 XEROPHYTES
(1) Succulent xerophytes.
(2) Non-succulents, also called true xerophytes.
Succulent xerophytes – Some organs become swollen and fleshy
due to active accumulation of water
the bulk of the plant body is composed of water storing tissues.
 XEROPHYTE ADAPTATIONS
The structural modifications in Xerophytic plants may be of two
types

(i) Xeromorphic characters:

characters - genetically fixed and inherited - xeromorphic.
Halophytic mangroves and many other evergreen trees

(ii) Xeroplastic characters:

These features are induced by drought - with dry conditions.
They are never inherited.
These characters may disappear from plants - favourable
conditions
 MORPHOLOGICAL ADAPTATIONS
(A) ROOTS:

well developed root systems -profusely branched.

Roots - perennial xerophytes grow very deep and
reach the layers where water is available in plenty.
Root hairs are densely developed near the growing tips
These enable the roots to absorb sufficient quantity of water.
(B) STEM:

Hard and woody.

It may be either aerial or subterranean.
covered with thick coating of wax and silica as in Equisetum.
covered with dense hairs - Calotropis.
stems – modified - thorns, e.g., Duranta, Ulex,
 MORPHOLOGICAL ADAPTATIONS
ULEX

DURANTA DURANTA
 MORPHOLOGICAL ADAPTATIONS
(B) STEM:
Succulents - main stem itself becomes bulbous and fleshy
Example: Kleinia articulata.
Stems - modified into leaf-like flattened, green and fleshy
structures as phylloclades. Example: cacti and cocoloba
In Ruscus plants - metamorphosed into leaf-like structures, the `
In Asparagus - Axillary branches - modified into small needle-like
green structures - called cladodes.
Euphorbia also develop succulence and become green.
leaves are greatly reduced, photosynthesis - phylloclades or
cladodes which are modified stems.
MORPHOLOGICAL ADAPTATIONS
Kleinia articulata

cacti cocoloba
 MORPHOLOGICAL ADAPTATIONS
(C) LEAVES:
Leaves - caducous, i.e., they fall early in the season,
Majority - reduced to scales
Casuarina, Ruscus, Asparagus
Provided with thick cuticle and dense coating of wax or silica.
May be reduced to spines
Ulex, Opuntia, Euphorbia splendens, Capparis and Acacia
Possess reduced leaf blades or pinnae
Have very dense network of veins.
Few species - green petiole swells and becomes flattened
taking the shape of leaf. This modified petiole is termed as
phyllode
The phyllode greatly reduces the water loss
 MORPHOLOGICAL ADAPTATIONS
Casuarina Ruscus Asparagus

Euphorbia splendens Capparis Acacia

 MORPHOLOGICAL ADAPTATIONS
(C) LEAVES:
leaves are covered with thick hairs - protect the stomatal
guard cells - check the transpiration.
Those xerophytes which have hairy covering on the leaves
and
stems are known as trichophyllous plants.
Zizyphus, Nerium, Calotropis procera
 ANATOMICAL ADAPTATIONS
(i) Heavy:
Heavy cutinisation, lignification’s and wax deposition
Some plants secrete wax in small quantity
Shining smooth surface of cuticle reflects the rays of light
Does not allow them to go deep into the plant tissues.
Thus, it checks the heavy loss of water.
 ANATOMICAL ADAPTATIONS
(Ii) EPIDERMIS:
Cells are small and compact.
It is single layered
Nerium leaf - epidermis is two or three layered
Stems - the epidermal cells are radially elongated.
Wax, tannin, resin, cellulose, deposited - epidermis – screen
against - high intensity of light.
Reduces the evaporation of water
Certain grasses with rolling leaves - specialized epidermis.
Motor cells facilitate - rolling of leaves by becoming flaccid during
dry periods.
In moist conditions - normal turgidity - unrolling of the leaf
margins.
Bulliform cells are of common occurrence in the leaf epidermis of
sugarcane, bamboo, Typha and a number of other grasses.
 ANATOMICAL ADAPTATIONS
(iii) HAIRS
Hairs are epidermal in origin.
simple or compound, uni / multicellular.
compound hairs are branched at the nodes.
These hairs protect the stomata and prevent excessive water loss.
surfaces of stems and leaves develop characteristic ridges and
furrows or pits.
 ANATOMICAL ADAPTATIONS
(iv) Stomata:
reduction of transpiration is of utmost importance.
possible only - stomatal number per unit area is reduced
No of stomata per unit area of leaf is greater than in mesophytes.
sunken type/ furrows or pits.
Walls of the guard cells and subsidiary cells are heavily cutinized
lignified in many xeric plants.
 ANATOMICAL ADAPTATIONS
(v) Hypodermis:
one or several layers of thick walled hypodermis.
derived from epidermis or from the cortex (stem) or from the
mesophyll (leaf).
The hypodermal – filled – tannin
(vi) Ground tissue:
Stem - majority - sclerenchyma.
Leaves - greatly reduced or they fall in the early season,
The photosynthetic activity – by outer chlorenchymatous cortex
In succulent stems and leaves, ground tissues are filled with thin
walled parenchymatous cells
makes the stems swollen and fleshy
leaves, mesophyll is very compact
intercellular spaces are greatly reduced.
Palisade tissue develops in several layers.
xylem and phloem, develop very well in the xerophytic body.
ANATOMICAL ADAPTATIONS
PHYSIOLOGICAL ADAPTATIONS
Assumption - structural adaptations - useful - reducing the
Works of Maximov support that
Except succulents, true xerophytes show very high rate of
transpiration.
The rate of transpiration per unit area in xerophytes is much
higher than that in mesophyte.
Stomatal frequency per unit area of leaf surface is also
greater than that in the mesophytic leaf.
 PHYSIOLOGICAL ADAPTATIONS
Succulents - contain polysaccharides, pentosans, acids - able to resist
drought.
Pentosans have water binding property.
These pentosans together with nitrogenous compounds of the
cytoplasm cause accumulation of excess amount of water in the cells
and consequently the succulence develops.
stomata open during night hours and remain closed during the day.
In dark, these plants respire and produce acids.
The heavy accumulation of acids in the guard cells increases osmotic
concentration – causing inward flow of water in the guard cells.
When guard cells- turgid - stomata open.
In the sunlight, acids - produce carbon dioxide – photosynthesis
so osmotic concentration of cell sap decreases which ultimately
causes closure of stomata.
 PHYSIOLOGICAL ADAPTATIONS
The chemical compounds of cell sap - converted - wall forming
compounds - incorporated into the cell walls.
Conversions of polysaccharides into anhydrous forms as cellulose,
formation of suberin
Enzymes, such as catalases, peroxidases, are more active in
xerophytes than in mesophytes.
Drought resistant - also in the resistance of the hardened
protoplasm to heat and desiccation.
Presence of the cuticle, polished surface, compact cells
sunken stomata protected by stomatal hairs regulate the
transpiration.
High osmotic pressure which increases the turgidity.
The turgidity of cell sap exerts tension force on the cell walls.
Wilting of cell is prevented.
High osmotic pressure of cell sap also affects the absorption of water
 HALOPHYTES
Plants grow & complete life cycle - with a high salt content are known
salt plants or halophytes.
They cannot avail of the water - of high concentration of salts in the
soils.
Thus, the halophytes are plants of physically wet but physiologically
dry habitats.
In the salt tolerant, the protoplasm functions normally and endures a
high salt concentration without apparent damage.
In – Rajasthan the soils are very salty because of presence of sodium
chloride, calcium sulphate, sodium bicarbonate, potassium chloride,
etc.
Chaenopodium album, Suaedafructicosa, Haloxylon salicorneum,
Salsola foestida, Tamara articulata grow very successfully and form
micro-edaphic formations.
 HALOPHYTES
Classification of Saline Habitats which is as Follows:

1. Aquatic-haline

2. Terrestro-haline
(a) hygrohaline
(b) mesohaline
(c) Xerohaline

3. Aero-haline

(a) Habitats affected by salt spray (maritime)

(b) Habitats affected by salt dust (salt desert)
 MORPHOLOGICAL ADAPTATION
(a) ROOTS:
Halophytes develop many shallow normal roots.
many stilt or prop roots develop from the aerial branches of –
anchorage in muddy or loose sandy soil.
These roots grow downward and enter the deep and tough strata of
the soil. In some plants, e.g., Rhizophora mucronata,
In some plants, the stilt roots may not at all develop
a large number of adventitious root buttresses develop from the
basal
parts of tree trunks - support to the plants.
The soil in coastal region is poorly aerated
In order to compensate this lack of soil aeration, the hydro
halophytes
develop special type of negatively geotropic roots, called
pneumatophores or breathing roots
 MORPHOLOGICAL ADAPTATION
Pneutamophores of mangroove plant
MORPHOLOGICAL ADAPTATION
The pneumatophores usually develop from the underground roots
They appear as peg-like structures.
The tips - pointed.
They possess numerous lenticels or pneumathodes on their
surface & aerenchyma - internally.
The gaseous exchange takes place in these roots through the
lenticels.
The aerenchyma - conduction of air down to the subterranean or
submerged roots.
Pneumatophores do not develop in some species of Rhizophora
 MORPHOLOGICAL ADAPTATION
(b) STEM:

Stems in several halophytes develop succulence.

Example: Salicornia herbacia
succulence depends on the ratio of absorbed to free ions in
the plant cells
salinity inhibits the cell division and stimulates cell
elongation.
The temperate halophytes are herbaceous
The tropical ones are mostly bushy and show dense cymose
branching.
Submerged marine angiosperms do not become succulent.
 MORPHOLOGICAL ADAPTATION
Salicornia herbacea

(c) Leaves:
The leaves are thick, entire, succulent, generally small-sized
Glassy in appearance.
Stems and leaves of coastal aero halophytes show additional
mode of adaptation to their habitats.
Their surfaces are densely covered with trichomes.
Leaves of submerged marine halophytes – thin
very poorly developed vascular system
frequently green epidermis.
They are adapted to absorb water and nutrients
 ANATOMICAL ADAPTATION
1. Large cells and I small intercellular spaces,
2. High elasticity of the cell walls,
3. Extensive development of water storing tissues,
4. Smaller relative surface area (surface/volume ratio),
5. Small and fewer stomata, and
6. Low chlorophyll content.
Anatomy of halophytes reveals a number of xerophytic features
Presence of thick cuticle on the aerial parts
The epidermis of xerosucculents and coastal halophytes - Cover of
waxy layers
Leaves may be dorsiventral or isobilateral.
They develop protected stomata which are not deeply sunken.
The palisade – layers of narrow cells with intercalated tannin and
oil cells example. Rhizophora mucronata
Mucilage cells may be found in abundance.
 ANATOMICAL ADAPTATION
Rhizophora mucronata
 ANATOMICAL ADAPTATION
Cortex is fleshy, several cells thick and in old stems
The leaves and stems - covered - various types of simple and
branched trichomes giving the plants a greyish appearance
Salt secreting glands may be found in some halophytes.
Pneumatophores develop a number of lenticels on their surface.
The cortex is spongy ,aerenchyma enclosing large air chambers.
They show conjoint, collateral vascular bundles with endarch
xylem at maturity
ANATOMICAL ADAPTATION
 PHYSIOLOGICAL ADAPTATION
Previously physiologically - drought - main cause of
developments of xeromorphy in halophytes,
Recent physiological experiments - xeromorphism in these plants
- purposeless adaptation.
This point is concluded taking into consideration the following
reasonable facts:
(i) They show high rates of transpiration,
(ii) They show exudation of sap that contains dissolved salts, and
(iii) They develop many shallow absorbing roots.
The halophytes show xeromorphism for enduring high salinity of
soil water and also for absorbing water with perfect ease
The significance of succulence is not so clearly understood.
Probably, it is induced by accumulation of salts in cytoplasm.
Sodium salts if present in the soil water will definitely stimulate
succulence even in non-halophytes
 EPIPHYTES
Epiphytes are amazing adaptors.
prime examples of how adaptation leads to survival in an
environment
Epiphytes are plants which grow above the ground surface, using
other plants or objects for support.
They are not rooted in the soil nor are they parasitic (i.e they do
not directly harm the other plant).
By growing on other plants, the epiphytes can reach positions
where the light is better or where they can avoid competition for
light.
common in some groups of plants, such as ferns, bromeliads
(members of the pineapple family, Bromeliaceae) and orchids
over half of the 20,000 species of orchids are epiphytic.
EPIPHYTES
 EPIPHYTES ADAPTATION
1. Awesome Design to take Advantage of Fewer
Epiphyte’s roots, flowers and fruits are specially designed to
help it survive – Scarce of - water, light and nutrients.
Rainforest canopies are dense with foliage, making it difficult for
any new plants to obtain sunlight for photosynthesis.
Epiphytes have adapted – live - branches of tall trees and vines –
access sunlight - lower levels plants of a rainforest canopy cannot.
RAIN FOREST CANOPY – COSTA RICA
 EPIPHYTES ADAPTATION
2. To live on other plants also requires specialized roots.
Epiphytes have a strong, thick root system - extremely efficient in
absorbing morning mist, rain and moisture from humidity.
Epiphytes’ roots obtain nutrients from leaf litter and other debris
The stems and leaves of epiphytes are also modified.
Bromeliads have stiff, upturned leaves that allow pools of water to
be stored.
Some species of bromeliads can hold up to 2 gallons of water!
Other modified leaves- Staghorn fern(Platycerium
madagascariense).
It has very thick and waxy leaves to retain moisture.
 EPIPHYTES ADAPTATION
3. Clever and Successful Reproduction Strategies:
The best part about survival of an epiphyte is to reproduce!
There are so many other plants in a rainforest that getting a
pollinator to take notice is a feat in itself.
Epiphytes put large amounts of energy into producing breath-taking
blooms, fruit, perfume and nectar to lure pollinators.
When pollination is successful, many epiphytes produce mass
numbers of seeds that can be transported by wind.
4. Relationships with surrounding organisms:
Epiphyte pollinators such as insects, birds and other small animals
use epiphytes as a food source.
In our Rainforest Dome, our Bananaquits (Coereba flaveola) are
constantly checking flowering plants for nectar:
Dead flowers, twigs and leaf litter - on the roots of epiphytes –
source of nesting material - birds
ll.
EPIPHYTES ADAPTATION
 PARASITIC PLANTS
plant that obtains all or part of its nutrition from another plant
causing extreme damage to the host
The defining structural feature of a parasitic plant - haustorium, a
specialized organ - penetrates the host and forms a vascular union
between the plants.
Parasitic plants differ from - climbing vines, lianas, epiphytes, and
aerophytes
Similar to parasitic plants, mycoheterotrophs - lack chlorophyll,
photosynthetic capacity,
but they live in symbiotic association with fungi
All parasitic plant species are angiosperms,
parasitism has evolved independently about 12 times
families - Balanophoraceaefamilies - Balanophoraceae,
Orobanchaceae, and Rafflesiaceae
Gymnosperm, Parasitaxus usta – proposed - parasitic, it actually
may be a mycoheterotroph as it appears to involve a fungal
symbiont.
 PARASITIC PLANTS
BalanophoraceaeBalanophoraceae
Rafflesiaceae

Orobanchaceae
 PARASITIC PLANTS
They have adapted the ability to fend for themselves in conditions
that lack available nutrients or where the competition for
nutrients is extreme.
Parasitic plants vary from those that are fully photosynthetic to
those that are just barely able to photosynthesize.
Parasitic plants have circumvented the need to find nutrients in a
small plot of soil by the development of a modified meristem root
called a haustorium that can penetrate the vascular system of
another plant, called a host, stealing vital mineral nutrients, water
and carbohydrates for its own benefit.
Parasitic plants - attack a host – ways - ranging from an attack on
the roots to an attack on the vascular tissue - stems.
Two examples of parasitic plants - mistletoe and the dodder vine.
PARASITIC PLANTS