Free Forms and Functions of Plants MCQs with Answers

241. Premature death of plants is caused by the deficiency of:

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

Explanation: The correct answer is Magnesium. Magnesium is a critical component of chlorophyll, and its deficiency leads to chlorosis-a condition where leaves turn yellow due to insufficient chlorophyll production. This can severely affect photosynthesis, leading to premature death in plants if not corrected. While iron deficiency also causes chlorosis, it does not usually lead to premature death unless it is severe and prolonged. Phosphorus and potassium deficiencies impact other aspects of plant growth and health, but they do not directly lead to premature death.

242. Shade loving plants are called:

• A. Halophytes
• B. Mesophytes
• C. Sciophytes
• D. Xerophytes

Explanation: Sciophytes are plants that grow in moderate to low intensity of light under the cover of large trees.

243. Light absorbing pigments in photosystem I is:

• A. P 600
• B. P 680
• C. P 700
• D. P 760

Explanation: Photosystem I has chlorophyll a molecule which absorbs maximum light of 700 nm and is called P700, whereas reaction center of photosystem II has P680

244. Accessory pigments are:

• A. Red-Yellow-Green
• B. Red-Orange-Blue
• C. Orange-Blue-Green
• D. Red-Orange-Yellow

Explanation: Accessory Pigments are the source of much of the RED-ORANGE-YELLOW coloration that we see in plant leaves.

245. Chemiosmosis occurs in the:

• A. Grana
• B. Stroma
• C. Thylakoids
• D. Intergrana

Explanation: In chloroplasts, chemiosmosis occurs in the thylakoids.

246. To decrease the salt potential, the guard cells absorb:

• A. Sodium Ions
• B. Magnesium ions
• C. Potassium ions
• D. Calcium ions

Explanation: Influx of potassium ions decreases water potential in the guard cell so water enters the cell from surrounding cells. As a result salt potential decreases.

247. The product of light dependent reactions are:

• A. RuBP + ATP
• B. RuBP + PGAL
• C. NADPH + ATP
• D. PGAL + ATP

Explanation: The two products of light dependent reaction of photosystem are ATP and NADPH.The light reaction is the first stage of the photosynthesis process in which solar energy is converted into chemical energy in the form of ATP and NADPH. The three products of the light reaction of photosynthesis are ATP, NADPH, and O2.

248. Chlorophyll is protected from intense light by:

• A. Phytochrome
• B. Phytokinin
• C. Phytocyanin
• D. Carotenoids

Explanation: Some carotenoids protect chlorophyll from intense light by absorbing and dissipating excessive light energy, rather than transferring energy to chlorophyll.

249. Carotenoids pigments are:

• A. Yellow, Red, Green, Blue
• B. Orange, Yellow, Red, Brown
• C. Green, Yellow, Blue, Brown
• D. Blue, Red, Green, Yellow

Explanation: Photosynthetic organisms contain light-absorbing molecules called pigments that absorb only specific wavelengths of visible light while reflecting others. The set of wavelengths absorbed by a pigment is its absorption spectrum. The set of wavelengths that a pigment doesn't absorb is reflected, and the reflected light is what we see as color.Carotenoids are accessory pigment molecules that may be yellow, orange, red, or brown. They absorb light energy and transfer it to the primary pigment molecules (chlorophyll-a) within the reaction center. Carotenoids also protect the primary pigments from excessive light (photoprotection). They absorb violet and blue-green light. There are two major types of carotenoids: the hydrocarbon class, or carotenes, and the oxygenated (alcoholic) class, or xanthophylls.

250. Excited electrons from photo system-II are captured by:

• A. PC
• B. PQ
• C. Cytochrome-b
• D. Pentamerous

Explanation: Plastoquinone (PQ) is the correct answer as it accepts excited electrons from photosystem-II and transfers them down the electron transport chain. Plastocyanin (PC) and Cytochrome-b are involved in the electron transfer process but do not directly capture excited electrons like plastoquinone does. The term 'Pentamerous' is unrelated to the process of capturing excited electrons in photosynthesis.