Plant Kingdom Test - 25

Cyanophyceae are blue-green algae and not brown. Bacillariophyceae is a very common phytoplankton, but does not belong to the group of brown algae. Rhodophyceae is red algae and not brown. The Phaeophyceae is brown algae, of mostly marine multicellular algae, including many types of seaweed. They play an important role in marine environments, both as food and for the habitats they form. Some of them may extend to large areas and form underground forests. Sargassum, creates unique habitats in the tropical waters of the Sargasso Sea. Many brown algae, grow along rocky seashores like members of Fucales. Some brown algae such as kelp are used as food by humans. Thus, the correct answer is option C.

The sea lettuces comprise the genus Ulva, a group of edible green algae, that is widely distributed along the coasts of many oceans of the world. The lettuce type species within the genus Ulva is Ulva lactuca, lactuca is the Latin name for "lettuce". Few members of this genus are known under the common name, green nori. Individual blades of Ulva can grow more than 400m but this only occurs when the plants are growing in sheltered areas. Thus, the correct answer is option A.

Perennation is the ability of the plant to survive under unfavourable condition. Auxospores typically play a role in growth processes, sexual reproduction or dormancy. So, the correct answer is option D.

Heterocysts are specialized, pale-yellow, thick-walled cells with the function of nitrogen-fixing formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale, and Anabaena sphaerica. They fix nitrogen from di-nitrogen (N$$_2$$) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis. Nitrogenase is inactivated by oxygen, so the heterocyst must create a micro anaerobic environment. Hence, their main function is nitrogen fixation. Thus, the correct answer is option B.