Hydrophytic Habitat

It is a habitat with excessive water supply. The plants growing in such a habitat do not face the problems of water loss due to transpiration, wilting and drought, They are known as hydrophytes.

Xerophytic Habitat

It is a very dry habitat with water shortages. The plants are called as xerophytes. They have diverse forms and undergo structural and physiological adaptations or modifications to reduce the rate of transpiration.

Hydrophytes

Hydrophytes grow in habitats where water is in excessive supply. They can be further categorised into the following six groups.

Free - Floating

These plants float freely and independently on the water surface.

Examples: Eichhornia, Pistia, Wolfia and Lemna.

Rooted with Floating Leaves

These plants remain attached to the bottom by their roots. But the leaves have long petioles which help to keep the leaves floating on the surface of the water.

Examples: Trapa, Nelumbo and Nymphaea.

Submerged Floating

These plants remain completely submerged in water but are not rooted in the mud.

Example: Ceratophyllum

Submerged and Rooted

These plants remain completely submerged in water and also remain rooted in the mud.

Examples: Hydrilla, Vallisneria

Amphibious and Rooted

These plants grow in water logged soils.

Examples: Polygonum, Marsilea

Emergent and Rooted

These plants grow in shallow waters and remain attached to the bottom. In plants such as Sagittaria and Ranunculus, the shoots are partly in water and partly exposed to air. In Scirpus, the shoots are completely exposed to air.

To live in aquatic habitats, the hydrophytes are characterised by many special morphological and anatomical features.

Adaptations

• The roots are either poorly developed, for example Hydrilla or completely absent as in Ceratophyllum

• The root cap is replaced by root pockets.

Example: Eicchornia

• The stem is long, slender, spongy and flexible.

Example: Hydrilla

• The leaves are thin, long and ribbon shaped as in Vallisneria or finely dissected as in Ceratophyllum

• Floating leaves are large, flat and entire.

Example: Nelumbo, Nymphaea

• The leaves are coated with wax.

• In Eichhornia the petiole becomes swollen and spongy

• Heterophylly is seen in some plants where aerial leaves are broad and submerged leaves are dissected. For example Ranunculus.

• The stem has large air chambers to store air for buoyancy.

• Mechanical tissue is either absent or poorly developed.

• Cuticle is either completely absent or if present it is thin and poorly developed.

• Vascular tissues are poorly developed.