Question

Halophytic green alga Dunaliella stores :
A. Glycerol
B. Sorbitol
C. Proline
D. None of the above

Answer 1

Hint:-Dunaliella is a halophytic alga and it does not possess a rigid cell wall. So, to survive, the organism uses high concentration of glycerol to maintain or to protect it against the osmotic pressure.

Complete answer:
Dunaleilla lacks a rigid cell wall, which makes it susceptible to osmotic pressure. Glycerol is used as a means by which the organism maintains both osmotic pressure as well as enzymatic activity. As it lives in the hyper saline environment glycerol plays a very important role.
A high concentration of glycerol can be preserved by maintaining a cell membrane having low permeability of glycerol. It also produces a huge amount of glycerol from the starch in response to high concentration of salt that is to the outside the cell. This is the reason it tends to grow vigorously in highly salt containing environments.
The chloroplast can hold large amounts of Beta-carotene, which makes it appear orange-red. The beta-carotene appears to protect the organism from long-term UV radiation that Dunaliella is exposed to in its typical environments.

Hence, the correct option is (A) Glycerol.

Additional Information:
Dunaliella has antioxidant activity due to its ability to produce high amounts of carotenoids. It is used in cosmetic and nutritional supplements as well. Due to the abundance of beta-carotene, which is an anti-oxidant as well as a vitamin A precursor, Dunaliella is a famous pro-vitamin A food supplement and also a component in cosmetics. Dunaliella may also be a source of vitamin B. Dunaliella is commercially used for the production of beta carotene.

Note:- It is only due to glycerol that Dunaliella tends to survive in the seawater. Species in the genus Dunaliella are morphologically similar to chlamydomonas with the main exception being that Dunaleilla lacks both a cell wall and a contractile vacuole.