Question

Hygroscopic roots occur in
(i) vanda
(ii) Rhizophora
(iii) Bryophyllum
(iv) All the above

Answer 1

Hint: Epiphytes form dense root systems that have a large surface area, enabling the plants to absorb rainfall. Hygroscopic roots possess these epiphytes.

Complete Answer:
- Epiphytic roots are also called ‘hygroscopic roots’. These roots grow in a few orchids which develop as epiphytes on the tree branches. They hang on independently in the environment and collect moisture with the support of specific tissue known as velamen. Velamen is a change of epidermis.
- Hygroscopic roots are those roots which absorb water from the atmosphere with specialized dermal tissue. Hygroscopic roots are found in Vanda. Epiphytic species of Vanda possess very large and modified aerial root systems. These aerial roots are used for intake of nutrient and water absorption like in other roots. They are also utilized as structure and to reach the surface. These roots function like regular terrestrial roots.
- In several species of Rhizophora ( for example Rhizophora mucronata) the stilt roots extend more than a meter above the soil surface and contain many pores called lenticels.
Bryophyllum pinnatum is a moist hairless herb 0.3-1.2 m length. Stems include four angled, adult one are light coloured and new ones are reddish speckled with white.

Thus, the correct option is (i) i.e. vanda.

Note: Epiphytes are called “air plants” due to the fact that they are not held in the soil. Epiphytes obtained food from rainwater, air and from other components. There are many acceptances found in the epiphytes to absorb nutrients and for survival. Epiphytes are present on shoot parts, leaves and other surfaces of plants. These epiphytic roots are known as hygroscopic roots.