Ecological groups are defined as groups of plants that grow under the same environmental factors. There are four main ecological groups: hydrophytes, xerophytes, halophytes, and epiphytes. Hydrophytes grow in or near water and have adaptations like reduced roots and stems, thin leaves, and air cavities for gas exchange. Xerophytes grow in dry areas and have adaptations like deep roots, small or absent leaves, waxy coatings, and succulence to retain water. Halophytes grow in saline soils and have adaptations like succulence, salt glands, and negative geotropism. Epiphytes grow on other plants and have clinging roots and thick leaves and cut

1. Ecological groups

2. ECOLOGICAL GROUPS
‘Groups of plants growing under
the same set of environmental
factors constitute ecological
groups’

3. In 1895 warming classified plants
into ecological groups
On the basis of ;
Type of substratum
Adaptic factors of the soil
Ecological groups of plants
Hydrophytes Xerophytes Epiphytes Halophytes

4. HYDROPHYTES

5. HYDROPHYTES
• Grow in water or in soil which is saturated
with water
• Water may be fresh or saline
• Lakes ,ponds,pools,rivers,etc. Constitute fresh
water bodies
• Phytoplanktons ;non vascular hydrophytes
• Vascular hydrophytes may arranged to 3
natural groups they are,

6. 1. Rooted and Submerged plants
• Anchored (rooted) hydrophytes
• Completely submerged in water
• Restricted to shallow areas where
they get adequate supply of light

7. They are of two types
1.Plants with long stems
They bear small leaves at the nodes
hydrilla
ceratophyllum

8. potamogetoa

9. 2.Plants with tuberous stem
They bear cauline leaves .the leaves are thin and
ribbon shaped.
Vallisneria nymphaea

10. 2.FLOTING PLANTS
They are of two types
Free floating forms
• Not attached to the soil
• Floating
• Grow in large numbers
• Some forms have very large leaves and rise
above water eg.water hyacinth

11. •Some smaller forms are
Pistia salvinia
azolla

12. •Plants like utricularia normally remain just
below the surface of water and are rootless

13. Floating but rooted forms
• Rooted in mud
• Possess floating leaves
• Grow in shallow regions
Water lilly lotus(nelumsium)

14. Victoria regia

15. 3.AMPHIBIOUS PLANTS
• Inhibits shallow water
• Form the marshy or shallow vegetation
• The basal part is submerged in water and
shoots extends well above the soil

16. typha sagittaria
hydrophylla

17. ADAPTATIONS OF
HYDROPHYTES
• Roots are reduced in size,unbranched and
without root hairs
• Stem is thin and delicate due to the lack of
mechanical tissues
• Leaves are reduced in size and are
thin,linear,or ribbon like to escape the effects
of strong water currents
1.SUBMERGED PLANTS
MORPHOLOGICAL ADAPTATIONS

18. Hydrilla with small leaves,small
roots,and tuberous stem

19. ANATOMICAL ADAPTATIONS
• They lack cuticle or suberin
• Conducting elements are very few and non
lignified
• Large number of air cavities for gas exchange
and storage
• Mesophyll is undifferentiated to palisade and
spongy tissue
• It is mostly of spongy type
• Chloroplasts are present in the epidermal cells

20. •Stomata is absent or non functional
•Absence of sclernchyma and collenchyma

21. 2.FREE FLOATING PLANTS
• Extremely reduced roots
• Root hairs are absent,special structures known
as root pockets are present insted of root caps
MORPHOLOGICAL ADAPTATIONS
Azolla plant with
extremely reduced
roots

22. • Roots are absent in
wolffia,utricularia,ceratophyllum etc.
• Stem is extremely reduced but leaves are
quite well developed
Water hycinth with small roots but well developed leaves

23. ANATOMICAL ADAPTATIONS
• Well developed air cavities are present in
stems ,leaves, and roots
• Collenchyma and sclerenchyma are
completely absent
• Vascular tissues are poorly developed
• Stomata are present at the upper surface of
leaves
• Palisade parenchyma is developed towards
the upper surface

24. FLOATING BUT ROOTED PLANTS
• Poorly developed roots
• Roots are produced from horizondal stems,
rootstocks or tubers
• Elongated and well developed petiole
MORPHOLOGICAL ADAPTATIONS

25. Well
developed
petioles

26. ANATOMICAL ADAPTATIONS
• Well developed air cavities are present in
petioles
• Leaves are covered with wax
• Stomata are present on the upper surfaces of
leaves
• Palisade parenchyma is developed but the
spongy parenchyma is in far excess. the later
enclose large air cavities
• Mechanical and vascular tissues are extremely
reduced

27. 3.AMPHIBIOUS PLANTS
• Well developed root system
• Plants have rhizomes which lie in the mud and
may show hydric and xeric adaptations
• Heterophylly(presence of more than one type
of leaves) is exhibited, submerged leaves are
normally disected and the lobes are linear and
thin
MORPHOLOGICAL ADAPTATIONS

28. ANATOMICAL ADAPTATIONS
• Aerenchyma and storage parenchyma are
present
• Mechanical and conducting elements are
present
• Thick walled endodermis to check loss of
water
• Large air chambers are present. which are
separated by diaphragms

29. XEROPHYTES

30. XEROPHYTES
• Plants which grows in xeric habitat such as
* places like deserts, plain peaks, sand hills
* shortage of water
*high rate of transpiration
• they are modified to withstand unfavourable
conditions

31. Classification of xerophytes
• Depending upon the ability of xerophytes to
withstand unfavourable situation they are
classified as;
1.drought escaping
2.drought evading
3.drought enduring
4.drought resisting

32. 1.Drought escaping (ephemerals)
• They are annuals
• Very short growing and flowering season
• Complete their life cycle in 4-6 weeks
• Found growing in semi arid region having
a brief rainy season

33. Arabidopis thaliana Alyassum alyssoides

34. 2.Drought evading
• Very small in size
• Have restricted growth and require very
low amount of water for growth and
development
• They conserve whatever little amount if
light they get and evade drought

35. Ambrosia dumosa Encelia farinosa
(white bursage) (brittle bush)

36. 3.Drought enduring(non-succulents)
• Slow growing shrubs
• They are small and have stunted growth
• They endure long dry periods when there is
acute shortage of water
• Extremely restricted growth
• Leaves wilt and fall down during unfavourable
season
• Resume growth in turn of favourable growth

37. Larrea tridentata (creosote bush)

38. 4.Drought resisting(succulents)
• They have thick and fleshy stems or leaves
• They store large amount of water and resist
drought
• Have well extended root system for water
absorption
• With the help of stored water they continue
their growth, flowering and fruiting

39. Agave Aloe
Euphorbia opuntia

40. MORPHOLOGICAL ADAPTATIONS
• They are provided with
a very deep and
extensive root system
for water absorption. it
is almost 129 feet
below the soil
• The stem is stunted in
growth and form a
bushy appearance

41. • Presence of
underground stems to
tide over the dry season
eg.saccharum
• Presence of hard and
woody stems
eg.acacia,prosopis,zizyp
hus
• Capparis aphylla have
completely dispensed
with leaves to check
transpiration
Prosopis with woody
appearance

42. • Leaves are reduced to
small scaly or spiny
structures
eg.ruscus,asparagus,cas
aurina
• Microphyllus leaves are
present in many
xerophytes
• Plants like nerium have
shining surfaces to
reflect away light and
heat
Asparagus

43. • The leaves of many xerophytic plants
have a waxy coating on the upper
surface. they are also covered with a
dense mass of hairs

44. ANATOMICAL ADAPTATIONS
• Presence of thick cuticle on the upper and
lower surface of leaves
• Thick epidermal walls
• Presence of multiple epidermis on leaves
eg.nerium
• Stomata are greatly reduced in number and is
restricted to lower surface
• Stomata are situated in deep pits and those
• pits are filled with hairs eg.nerium

46. • Sclerenchymatous hypodermis eg.pinus
needle
• The spongy parenchyma cells are
comparatively fewer and have very small inter
cellular spaces
• Presence of small cells and small vacuoles to
maintain protoplasmic stability
• The protoplasam is not easily pulled away
from the cellwall and therefore the
plasmodesmata do not get ruptured
• Well developed xylem and phloem

47. Physiological adaptations
• Thick cell sap

48. HALOPHYTES

49. • Inhabit in saline soils
• Tolerant to a high concentration of soluble
inorganic salts
• The plants are affected by these dissolved
inorganic salts
• The effect may be partially osmotic and
partially chemical
• To maintain turgidity cell sap is much more
concentrated

50. SALIENT FEATURES OF
HALOPHYTES
• A vast number of halophytic flora are
succulents
• Leaves may be thin ,small leathery, and spiny
to minimise loss of water in transpiration
• They have evergreen leaves which have water
storage tissue, prominent palisade cells, and
thick cuticle

51. • They are provided with
negatively geotropic
pneumatophores for
gaseous exchange
eg.mangrooves
• Some halophytes
exhibit vivipary
ie,seeds germinate
before the fruits break
off the plants
• Salt glands are
presesnt

52. TYPES OF HALOPHYTES
• They grow on rocks near the rocks
1.LITHOPHILOUS
2.PSAMMOPHILOUS
•They grow on sandy region
3.PELOPHILOUS
They grow in places where the saaline soilloam
with a predominance of clay

53. 4.SALT SWAMP AND SALT DESERT
• They grow in calm water and muddy spots
5.MANGROVES
• Mangroves or littoral swamp forest grow on
sea shores in tropical and sub tropical regions

54. MANGROOVES
• In tropical and subtropical regions halophytes
form a typical sea shore vegetation called
mangrooves
• Mangroves are present in suderbans,on the
coasts of Mumbai and Kerala,
• Their osmotic potential is maintained at a low
level to facilitate absorption of water from sea

55. MANGROOVES IN KERALA
• In Kerala mangroves are distributed in all the
districts except Idukki, Pathanamthitta,
Palakkad and Wayanad.
• Maximum extent is reported from Kannur
district.
• The total extent of mangrove forests in the
state is estimated to be less than 50km2
(Mohanan 1997) .

56. MAIN SPECIES
• Acanthus cillicifolius,
• Acrostichum aurem,
• Aegiceras corniculatum,
• Avicennia officinalis,
• Azima tetracantha,
• Bruguiera gymnorrhiza,
• B. cylindrica,
• B sexangula,
• Excoecaria agallocha,
• E indica,
• Kandelia candel,
• Rhizophora apiculate,
• R mucronata,
• Sonneratia caseolaris,
• Calophyllum etc.

57. ADAPTIC FEATURES OF
MANGROOVES
• STILT ROOTS
• PNEUMATOPHORES :special negatively
geotropical roots for absorbing atmospheric
oxygen
• VIVIPARY :seeds start germinating while fruit is
still attached to the mother plant
• SHRUBY AND WOODY NATUER
• SALT GLANDS; salt glands are present

58. EPIPHYTES

59. EPIPHYTES
• Plants which grow on other plants
• But will prepare their on food unlike parasites
• Grow in places where there is regular rainfall
and plenty of humidity in the atmosphere
• They bears three types of roots,clinging
roots,velamen roots,and areal roots
• They produce large amount of seeds

61. ADAPTATIONS TO CHEK
TRANSPIRATION
• Few leaves
• Thick leathery or
succulent leaves
• Thick cuticle
• Sunken stomata

62. Classification of epiphytes
• A number of species of family
Asclepiadaceae,Pepromia,and a few ferns
drive their nutrition from the host and
atmosphere
1.Proto epiphyte
2.Hemi epiphyte
•Their epyphytism is linked to their early
developmental stages which they complete on
certain hosts

63. •Later they grow on ground with their on roots
and behave as completely independent plants
•Eg.ficus,fig trees etc.
3.Nest epiphyte
Many orchids form net like structures to collect
large quantities of humus and water

64. 4.Tank epiphyte
•The leaves are modified to pocket,funnel,or
spoon like structures to absorb humus and
mineral nutrients which accumulate in the bark
surface crevices of the host support.
• Peltate scaly hairs present on the base of the
leaves to absorb nutrients
•The root as are concerned only with the
anchorage of the epiphyte on the host

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