Free Forms and Functions of Plants MCQs with Answers

221. The molecular formula of chlorophyll b is:

• A. C55H70O6N4Mg
• B. C70H55O11N5Mg4
• C. C14H55O6N5Mg3
• D. C55H76O5N6Mg2

Explanation: The correct molecular formula of chlorophyll b is C55H70O6N4Mg. This formula indicates the presence of 55 carbon atoms, 70 hydrogen atoms, 6 oxygen atoms, 4 nitrogen atoms, and 1 magnesium atom. Option A is correct because it aligns with this molecular formula. Options B, C, and D have incorrect combinations of elements and quantities, making them incorrect choices for the molecular formula of chlorophyll b.

222. The complex force of photosynthesis can be studied by the use of one of the following isotopes :

• A. 6C14
• B. 1H2
• C. 2He4
• D. 6O16

Explanation: Oxygen-16 is the ideal isotope for studying photosynthesis because it allows for precise measurements of oxygen uptake and flow during the process. Carbon-14, Hydrogen-2, and Helium-4 are not commonly used for this specific purpose, making them incorrect choices for this question.

223. Which of the following is present in the center of the Porpyrine ring of chlorophyll?

• A. Iron
• B. Sodium
• C. Potassium
• D. Magnesium

Explanation: The porphyrin ring of chlorophyll contains a magnesium atom at its center. Magnesium is a critical component of chlorophyll, responsible for capturing light energy during photosynthesis.

224. Phloem tissues are composed of:

• A. Tracheids
• B. Trachea
• C. Collenchyma
• D. Sieve tubes

Explanation: Phloem tissues are composed of sieve tubes, which are specialized cells responsible for transporting organic materials, such as sugars, throughout the plant. They form the main conducting elements of the phloem.

225. Stream of chloroplasts carries the fixation of:

• A. Nitrogen
• B. Oxygen
• C. Carbon monoxide
• D. Carbon dioxide

Explanation: Chloroplasts are the site of photosynthesis in plant cells, where carbon dioxide (CO2) is fixed into organic molecules. The process involves light-dependent reactions in the thylakoid membranes and light-independent reactions in the stroma. The enzyme Rubisco facilitates the fixation of CO2 into glucose during the Calvin Cycle.Option A (Nitrogen): Nitrogen fixation is carried out by specialized bacteria, not chloroplasts.Option B (Oxygen): Oxygen is released as a byproduct of photosynthesis, not fixed.Option C (Carbon monoxide): Carbon monoxide is not involved in the photosynthetic process and is harmful to plants.

226. Plant cells synthesize sugar in the;

• A. Thylakoid
• B. Grana
• C. Stroma
• D. Christa

Explanation: Plant cells synthesize sugar in the stroma of chloroplasts. The stroma contains the enzymes necessary for the Calvin cycle, which is the process that converts carbon dioxide and other compounds into glucose. The thylakoids and grana are involved in the light-dependent reactions that produce ATP and NADPH, which are then used in the stroma for sugar synthesis. Christa is unrelated to chloroplasts and pertains to mitochondrial structure.

227. Chlorophyll II is protected from intense light by

• A. plant hormones
• B. carotenoids
• C. plant enzymes
• D. water present in mysophyll tissue

Explanation: Carotenoids are the photoprotective pigments that absorb light of high intensity and transfer the energy to chlorophyll for photosynthesis, thereby playing an important role in photosynthesis.

228. Chlorosis in plants is caused by the deficiency of:

• A. nitrogen
• B. magnesium
• C. potassium
• D. both a and b

Explanation: Chlorosis is the yellowing of leaves due to a lack of chlorophyll, often caused by nutrient deficiencies. Nitrogen is a vital component of chlorophyll, and magnesium is part of the chlorophyll molecule. Therefore, deficiencies in nitrogen and magnesium can both result in chlorosis. Potassium, while important for various plant functions, does not directly affect chlorophyll production, so its deficiency does not typically cause chlorosis.

229. The earlyis fall of leaves and fruits in plants in caused by the deficiency of:

• A. phosphorus
• B. potassium
• C. magnesium
• D. nitrogen

Explanation: The correct answer is phosphorus. Phosphorus is essential for the development of roots, flowers, seeds, and fruit. Its deficiency can lead to poor structural integrity and premature abscission, or the dropping of leaves and fruits. Potassium helps in the overall plant health and resistance to stresses but does not specifically prevent early leaf and fruit fall. Magnesium is crucial for chlorophyll production and photosynthesis but does not prevent abscission. Nitrogen is important for growth and green coloration but not directly involved in the prevention of early leaf and fruit drop.

230. Hydathodes are

• A. hormones secreting glands
• B. water secreting glands
• C. nectar secreting glands
• D. enzymes secreting glands

Explanation: Hydathodes are holes in leaf magrin through which water is secreted out during guttation.