Plant Kingdom Test - 27

Algae are a very large and diverse group of eukaryotic organisms, ranging from unicellular genera, such as Chlorella and the diatoms to multicellular forms such as, the giant kelp, a large brown alga that may grow up to 50 meters in length. Most are autotrophic and lack many of the distinct cell and tissue types found in land plants, such as stomata, xylem and phloem. Algae have photosynthetic machinery ultimately derived from Cyanobacteria, that produce oxygen as a by-product of photosynthesis. The photosynthetic yield of the protist autotrophic algae is 80%.

• Auxospores and hormocysts are formed by several diatoms and a few cyanobacteria respectively. Bacillariophyceae members (diatoms) are microscopic, eukaryotic, unicellular or colonial coccoid algae. These algae are sexually reproduced by the formation of auxospores in most cases. Bozi (1914) and Fermi (1930) reported that short sections of living cells at the tips of the trichomes of Wertiella Janosa become invested by a thick, lamellated, pigmented sheath. Such multicellular spore-like structures function as perennating bodies. They are specially modified hormones and are called homosporous or hormocysts.
  
• Hence Auxospores and hormocysts are formed respectively by Several diatoms and a few Cyanobacteria.
• So, the correct answer is 'Several diatoms and a few Cyanobacteria'.

Option A and C are correct as In Chlorophyceae, the stored food material is starch and the major pigments are chlorophyll a and b while, Floridian starch is the characteristic photosynthetic reserve substance of red algae, occurring abundantly in certain basin shaped grain cells. Most Rhodophyceae store starch outside the chloroplast, often as a cap over a bulging pyrenoid. The major carbohydrate storage product of red algae is a type of starch molecule (Floridian starch) that is more highly branched than amylopectin. Floridian starch is stored as grains outside the chloroplast. Thus, the correct answer is option C.

The algae which is not only edible but a rich source of protein is Chlorella. It is a potential food source because it is high in protein and other essential nutrients; when dried, it is about 45% protein, 20% fat, 20% carbohydrate, 5% fibre, and 10% minerals and vitamins. Mass-production methods are now being used to cultivate it in large artificial circular ponds. It is also abundant in calories and vitamins. When first harvested, Chlorella was suggested as an inexpensive protein supplement to the human diet.

Red tides are caused by dinoflagellates. Red tide is a common name for a phenomenon known as an algal bloom (large concentrations of aquatic microorganisms) when it is caused by a few species of dinoflagellates and the bloom takes on a red or brown color. Red tides are events in which estuarine, marine, or fresh water algae accumulate rapidly in the water column, resulting in coloration of the surface water. It is usually found in coastal areas.

Kelps are marine algae or large seaweeds or algae belonging to the brown algae; Phaeophyceae in the order Laminariales. Kelp grows in underwater forests called as kelp forests in shallow oceans. The organisms require nutrient-rich water with temperatures between $$6^0$$ C and $$14^0$$ C. They are known for their high growth rate.

Auxospore formation is a reproductive process of diatoms. Auxospores are specialised cells, that are produced at key stages in their cell cycle. Auxospores typically play a role in growth processes, sexual reproduction or dormancy. Auxospores are involved in re-establishing the normal size in diatoms, because successive mitotic cell division leads to a decrease in cell size. This occurs because each daughter cell produced by cell division inherits one of the two valves that make up the frustule - a silica cell wall, and then grows a smaller valve within it. Consequently, each division cycle decreases the average size of diatom cells in a population. When its size becomes too small, a dividing diatom cell produces an auxospore to expand its cell size back to that, which is normal for vegetative cells.

Pyrenoids are found most commonly in the chloroplast of green algae. These are associated with the operation of a carbon-concentrating mechanism (CCM). Their main function is to act as centres of carbon dioxide fixation.

Floridian starch is the characteristic photosynthetic reserve substance of red algae, occurring abundantly in certain basin-shaped grain cells. Most Rhodophyceae store starch outside the chloroplast, often as a cap over a bulging pyrenoid. The major carbohydrate storage product of red algae is a type of starch molecule (Floridean starch), that is more highly branched than amylopectin. Floridian starch is stored as grains outside the chloroplast. Thus, the correct answer is option B.

Bacteriological filter is a filter whose pores are fine enough to filter the bacteria and Cosmarium is a bacteriological filter because its cell membrane is highly porous that can filter organism as small as bacteria. Rest of the Algae don't possess this activity.