Question

Mannitol is stored food in
A. Chara
B. Porphyra
C. Fucus
D. Gracilaria

Answer 1

Hint:- Algae are autotrophic aquatic organisms that occur in a variety of habitats. They are the primary producers of many energy-rich compounds such as mannitol, starch, laminarin, etc. Mannitol is a sugar alcohol. They are carbohydrates with less calorie content and are sugar-free. It is useful as a diabetic sugar due to its sugar-free quality. They are used for medication.

Complete Answer:- Fucus belongs to the class Phaeophyceae or brown algae group. It is commonly called as rockweed. They are mainly marine algae. They contain several pigments such as Chlorophyll a, Chlorophyll c, and carotenoid pigment Fucoxanthin. These pigments impart their characteristic brown color. They have a disc-shaped holdfast for attachment to the substratum, a stalk-like stipe, and a leaf-like frond. Food is stored as mannitol and laminarin in Fucus and other brown algae. Their cell wall is made up of cellulose and a gelatinous coating of algin.
Chara belongs to the class Chlorophyceae or green algae which is green in color due to the dominance of Chlorophyll a and Chlorophyll b pigments. Nutrients are stored in the form of starch and oil droplets in green algae. They have stem-like and leaf-like structures that give them their appearance of land plants. Nitrogen-fixing cyanobacteria are seen on the surface of Chara.
Porphyra and Gracilaria belong to the class Rhodophyceae or red algae. The food storage material in red algae is Floridian starch. They contain Chlorophyll a, Chlorophyll b, and Phycoerythrin which give them their characteristic red color. Agar is extracted from Gracilaria.

The correct answer is Option C.

Note:- Fucus are industrially used for the extraction of algin or alginic acid present on their cell wall. The whole plant is used for medicinal purposes and as a dietary supplement due to the high amount of iodine, mannitol, bromine, and beta carotene present in it. They are dried, burned, and used as kelps or a kind of soda ash used for the manufacturing of soap, glass, etc. It is also used as a fertilizer in harvesting fields.