Question

Mannitol is stored food in-
a. Chara
b. Porphyra
c. Fucus
d. Gracilaria

Answer 1

Hint: Algae can either be autotrophic or heterotrophic in nature. They can store food in the body and the stored food is broken down when they need energy. In algae, stored food materials are present in the form of starch, oils, floridean starch, and laminarin. Mannitol is a type of stored food present in Phaeophyceae also known as brown algae.

Complete answer:
Algae are capable of storing food to produce energy when they are required. Starch, oils, floridean starch, laminarin are the food materials stored in algae. Mannitol is a form of complex carbohydrates stored as food in some definite algae.
The members of Phaeophyceae, also known as brown algae, stored food as mannitol. Mannitol represents the major end product in theses algae and is the main form of carbon storage. It is formed by reduction of fructose-6-phosphate. Another important utilisation of mannitol is its use as osmoprotectant as well as an antioxidant.

> Fucus are brown algae which is found in the intertidal zones of rocky seashores. These algae belong to the class Phaeophyceae and order Fucales, which stored food in the form of laminarin, mannitol, and oil. Mannitol is stored as a food reserve in Fucus. They are common littoral seaweed growing in the hard-rocky areas of the sea.

> Chara is a type of multicellular green algae that belongs to the genus of charophyte green algae. This type of algae is found in the family Characeae and the class Chlorophyceae. They are found in freshwater and grow submerged attached to the bottom. They stored food in the form of starch and oil.

> Porphyra is a variety of cold-water seaweed alga, growing in cold, shallow seawater. It is a type of red algae that belongs to the class of Rhodophyceae. The algae belonging to this class reserved their food in the form of floridean starch.

> Gracilaria is also a type of red algae that is notable for its economic importance. It also belongs to the class of Rhodophyceae and reserved food found in the Gracilaria in the form of floridean starch as in Porphyra.

Hence, the correct answer is option (C).

Note: Algae can reserve food in their body for their future requirements. The primary product as reserved food in algae is polysaccharides. Polysaccharides can be found in a different form in different types of algae. It can be stored in the form of starch, floridean starch, and mannitol. Mannitol is a form of complex carbohydrates which is stored in Fucus which belongs to Phaeophyceae.