Botany - Plant Kingdom Question with Solution | TestHub

Seaweeds contain carrageenan and alginate. Because of their water-holding properties, carrageenan and alginate are extracted from seaweeds and used to thicken a variety of foods, including soy milk, chocolate milk, etc.
Agar or agar-agar, is a jelly-like substance, obtained from red algae Gelidium and Gracilaria. Agar can be used as a laxative, an appetite suppressant, a vegetarian substitute for gelatin, a thickener for soups, etc. 
Chlorella and Spirulina are forms of alga and highly rich in nutrients. They are used as a food supplement by space travellers and athletes.
Mannitol is the stored food in Phaophyceae (brown algae) In Rhodophyceae stored food is floridean starch.