Question

Rhizophora is an example of
(a) Lithophyte
(b) Freshwater aquatic
(c) Mesophyte
(d) Halophyte

Answer 1

Hint: This plant is a salt-tolerant which can grow in the soil or water of high salinity. The roots or salt spray come in contact with saline water like in saline semi-deserts, mangrove swamps, sloughs, marshes, and seashores.

Complete answer:
Rhizophora is a mangrove plant and is an example of halophyte as it grows in high salt concentration waters. They have aerial roots to help in respiration. For instance, the salt marsh grass, Spartina alterniflora or smooth cordgrass is an example of a halophyte. Only 2 percent of all the plant species are halophytes. The salt tolerance or halotolerance is a measure used to decide the amount of salt content and is measured by the amount a plant can tolerate in the total dissolved solids in irrigation water. 40 gm/l of salt is present in seawater. Beans and rice tolerate only 1 to 3 grams per liter and can be said as glycophytes. The dwarf glasswort or Salicornia bigelovii is a good halophyte for use as a crop and can grow in 70 grams per liter of salt. Halophytes may not always take the form of salt tolerance; they can even avoid the salt content. Such plants which live in a saline environment but avoid the effects of high salt are known as facultative halophytes.
So, the correct answer is ‘Halophyte’.

Note: Most of the plant species are glycophytes i.e. they can't grow in a salt medium and are even damaged easily by high salinity. Research for halophytes as biofuel precursors is going on. Salicornia bigelovii a type of halophytes does not compete with food crops and can be grown in harsh environments thus they can be used as biodiesel or bio alcohol.