Ecological adaptations of plants found in hydro-phytic, xerophytic, halophytic and epiphytic conditions

Exercise 8: Ecological adaptations of plants found in hydro-phytic, xerophytic, halophytic and epiphytic conditions.

Aim: To study plants found in different habitats and comment upon their adaptations.

Principle: The modifications in the structure of organisms to survive successfully in an environment are called adaptations of organisms. Observe different plants existing under various ecological habitats. The corresponding adaptations of plants and their interaction with the environment can be better understood.

Requirements: Fresh or preserved specimens of Eichhornia, Opuntia, Avicennia and Vanda.

A. Adaptations of Hydrophytes - Eichhornia (Water hyacinth)

Eichhornia is a free floating hydrophyte that grows in ponds, lakes and water bodies containing fresh water.

Diagnostic Features

·        Root system is poorly developed.

·        Root pockets are present.

·        The petioles become swollen and spongy, providing buoyancy.

·        Cortex is well developed with numerous air chambers. It helps in buoyancy and rapid gaseous exchange.

·        Mechanical tissues are generally absent.

B. Adaptations of Xerophytes - Opuntia

Opuntia is a succulent or drought resisting xerophyte, which grows wild in arid areas.

Diagnostic Features

30.            The stem is flattened, green, thick and fleshly called phylloclade

31.            Mucilage is present which helps to retain the water.

Leaves are modified into spines

C.  Adaptation of Halophytes – Pneumatophores of Avicennia

Avicennia is a plant which grows and survives in saline environment like salty lakes and sea shores (mangrove vegetation).

Diagnostic Features

A special kind of negatively geotropic root called pneumatophores (respiratory roots) are present.

The leaves excrete salts through the salt glands.

D. Adaptation of Epiphytes – Vanda

Vanda is an epiphytic plant that grows perched on other plants (supporting plants). They use supporting plants only as shelter and not for water or food supply.

Diagnostic Features

·        Root system is extensively developed. These roots are of two types (1) clinging roots and (2) aerial roots.

·        The clinging roots fix epiphytes firmly on the surface of the supporting plant.

·        Aerial roots are green coloured, hang downwardly and absorbs moisture from the atomosphere with the help of spongy tissue called velamen.