In this presentation, concept of hydrophytes, types of hydrophytes and adaptations (morphological, anatomical and physiological) developed in them are explained.

1. Hydrophytes
Dr. Ravindra. D. Madhekar
Assistant professor,
Department of Botany,
S. B. E. S. College of Science,
Aurangabad
(Maharashtra)
India

2. Hydrophytes
• Greek, Hudor = water and Phyton = Plant; water plant.
• Grow in wet places or in water either partly or wholly
submerged.
• According to the way in which they develop in water,
further classified as :
1. Free floating : in contact with air and water but not
with the soil.
E. g. Wolffia, Lemma, Azolla, Salvinia, Pistia,
Echhornia etc.

3. Free Floating Hydrophytes
Azolla Salvinia
Pistia Eichhornia

4. 2. Rooted hydrophytes with floating leaves :
 Fixed in mud but leaves have long petiole floating on
the water surface.
 Remaining parts except leaves in water.
 E. g. Nelumbo, Nymphea, Marsilea etc.
Nelumbo, Nymphea

5. 3. Submerged floating hydrophytes :
submerged in water but not rooted.
E. g. Ceratophyllum, Utricularia
Ceratophyllum

6. 4. Rooted submerged :
Below the water surface but rooted in soil.
E. g. Hydrilla, Potamogeton, Isoetes, Vallisnaria, Chara etc.
Hydrilla Potamogeton
Vallisnaria Chara

7. 5. Rooted Emergent :
Shoots/Assimilatory organs partly or completly
underwater fixed in mud.
E. g. Saggitaria, Ranunculus, Scripus, Cyperus etc.

8. • Factors affecting the plants in aquatic
environment :
1. Temperature of water
2. Osmotic concentration of water
3. Toxicity of water
• The osmotic concentration and toxicity dependent upon
the amount and nature of chemical substances dissolved
in water.
• The physiology of aquatic plants is greatly affected by the
change in osmotic concentration of water.
• The aquatic plants are subjected to less extremes of
temperature because water is bad conductor of heat
• Hydrophytes less affected as the transpiration from the
plant tissue is completely out of question.

9. Hydrophytic Adaptations:
• As the aquatic environment is uniform throughout, the
hydrophytes develop very few adaptive features.
A. Morphological:
(I) Roots:
 Less significant and are of Secondary importance.
 Overall development is poor, may be entirely absent.
 If present – Adventitious, fibrous, reduced in length,
unbranched or poorly branched.
 In Salvinia, leaves compensate for roots.
 In emergent forms, roots well developed with distinct root
cap.
 Floating hydrophytes do not possess true root cap but very
often they develop root pockets/root sheaths.
 In Lemma, acts as simply balancing and anchoring organ.

10. Cont.
 In rooted hydrophytes like Hydrilla and Vallesnaria,
derive their nourishment from water by their body
surfaces, are partly dependent on their roots for
minerals from the soil.
 In Jussiaea repens,
two types of roots
develop :
(Normal and floating)

11. (II) Stem :
 In submerged form : longer, slender, spongy, flexible.
E.g. Hydrilla, Potamogeton.
 In Free floating : slender, floating horizontally on water
surface as in Azolla or thick, short, stoloniferous, spongy in
Eichhornia.
 In rooted hydrophytes with floating leaves : Rhizome
E. g. Nymphea, Nelumbo
 Vegetative propagation mainly by runners, stolons, stems,
root tuber, dormant apices, off sets.
 Most extensive and common method of reproduction.
 Most of them are perennial.

12. Hydrilla

13. (III) Leaves :
 In submerged form :
Leaves are thin, either long,
or ribbon shaped as in vallesnaria,
Long, linear in Potamogeton,
Finelly dissected in Ceratophyllum.
 In Floating hydrophytes :
Large, flat, entire, upper surface coated with wax in
Nymphea and Nelumbo,
Swollen and spongy in Eichhornia.
Petiole is long, flexible, and often covered with mucilage.

14. • In Emergent forms : Shows heterophylly.
• Submerged leaves are linear, ribbon shaped or highly
dissected.
• Floating leaves are broad, circular or slightly lobed.

15. B. Anatomical adaptations
(I) Roots :
 Cuticle is absent, if present poorly developed.
 Epidermis : single layered, made up of thin walled
parenchymatous cells.
 Cortex : well developed, made up of thin walled
parenchymatous cells, major portion occupied by well
developed air cavities (aerenchymatous) which offers
resistance to bending stress, increase buoyancy, and
allows rapid gaseous exchange.

16. • Vascular tissues : Poorly developed, less differentiated.
• Xylem : vessels are less common, tracheids generally
present.
• In floating forms i.e. Eichhornia differentiated to some
extent.
• In Emergent forms as Rannanculus and Typha,
comparatively much distinict and well developed.
• Mechanical tissues : generally absent except in some
emergent forms as Typha where pith cells are
parenchymatous.

18. (II) Stem :
 Cuticle is either absent or poorly developed and thin.
 Epidermis : made up of thin walled parenchymatous cells
and single layered.
 Rhizomes of Nymphea and Nelumbo shows well developed
epidermis.
 In emergent forms as Typha, cuticle and epidermis is well
developed.
 Hypodermis absent in submerged forms like Hydrilla and
potamogeton.
 In floating and emergent forms it may present and
parenchymatous/cholenchymatous

19.  Cortex : well developed, made up of thin walled
parenchymatous cells, traversed by air cavities, possess
chloroplast (Photosynthetic).
 In some as in Nymphea, large number of vascular
bundles scattered in cortex.
 Endodermis distinct in rhizome and similar organs.
 Vascular bundle lacks bundle sheath.
 Vascular elements : thin walled, lignified elements being
absent.
 In emergent forms : well differentiated and developed.
Mechanical tissues absent.

21. (III) Leaves :
 Cuticle usually absent in submerged forms like
Potamogeton.
 In floating forms as in Nymphea, poorly developed,
confined only to upper side and thin.
 In emergent forms, it is thin.
 Epidermis : Single layered, made up of thin walled
parenchymatous cells with abundence of chloroplast.
 Stomata completely absent in submerged leaves as in
Potamogeton. In floating leaves confined only to upper
surface of leaf. In emergent forms found on both
surfaces of leaf.
 Mesophyll tissue : undifferentiated in submerged
leaves, differentiated and presence of air cavities in
floating leaves

22. • Vascular tissues : very much reduced and sometime
difficult to be differentiated in to xylem and phloem as
in submerged form.
• In floating leaves as in Nymphea, xylem elements are
thin walled and phloem being well developed.
• In aerial leaves, vascular elements are comparatively
well differentiated with vessels in xylem elements.
• Mechanical tissues : well developed.
• Petioles : abundance of aerenchyma, thin walled cells,
lack of differentiation in vascular tissues and absence of
any lignified mechanical tissues.

24. C. Physiological adaptations :
• As habitat mostly deficient in oxygen content, having ability
to respire anaerobically or have low oxygen requirement.
• Special aerating organs are present.
• Osmotic concentration of cell sap is equal or slightly higher
than that of water.
• Submerged plants absorbs water through general plant
surface.
• Gases produced during photosynthesis and respiration partly
retained in air chambers to be utilised as and when required.
• Transpiration absent in submerged plants while excessive
rate in floating and emergent plants.
• Mucilage cells and canals protect the plant body from decay
under water.