1. Which phytochrome form is considered physiologically active and initiates most light-mediated responses in plants?

  • A. Pr
  • B. Pfr
  • C. Protochlorophyll
  • D. Phycobilin

Answer: B. Pfr

Explanation: Pfr is the biologically active form of phytochrome that regulates seed germination, flowering, and photomorphogenesis.

2. Which soil colloid possesses the highest cation exchange capacity per unit weight?

  • A. Kaolinite
  • B. Illite
  • C. Humus
  • D. Chlorite

Answer: C. Humus

Explanation: Humus has an exceptionally high cation exchange capacity (200–400 cmol(+)/kg), much higher than most clay minerals.

3. Which enzyme reduces nitrite (NO₂⁻) to ammonium (NH₄⁺) inside plant cells?

  • A. Nitrate reductase
  • B. Nitrite reductase
  • C. Glutamine synthetase
  • D. Nitrogenase

Answer: B. Nitrite reductase

Explanation: Nitrite reductase converts nitrite into ammonium in chloroplasts using reduced ferredoxin as the electron donor.

4. In plant breeding, the phenomenon where superior F₁ performance exceeds both parents is known as:

  • A. Epistasis
  • B. Inbreeding depression
  • C. Heterosis
  • D. Polyploidy

Answer: C. Heterosis

Explanation: Heterosis or hybrid vigor refers to the enhanced performance of F₁ hybrids over their parents.

5. Which insect hormone is primarily responsible for maintaining larval characteristics during molting?

  • A. Ecdysone
  • B. Juvenile hormone
  • C. Bursicon
  • D. Prothoracicotropic hormone

Answer: B. Juvenile hormone

Explanation: Juvenile hormone prevents metamorphosis and maintains larval features during successive molts.

6. Which micronutrient deficiency is commonly associated with 'Khaira disease' in rice?

  • A. Iron
  • B. Copper
  • C. Zinc
  • D. Manganese

Answer: C. Zinc

Explanation: Khaira disease is a characteristic symptom of zinc deficiency in rice, causing bronzing and stunted growth.

7. Which photosynthetic pathway exhibits the highest water use efficiency under arid conditions?

  • A. C₃ pathway
  • B. C₄ pathway
  • C. CAM pathway
  • D. Calvin cycle only

Answer: C. CAM pathway

Explanation: CAM plants open stomata at night, minimizing water loss and providing the highest water use efficiency.

8. Which statistical design is most suitable when experimental material is highly heterogeneous in two directions?

  • A. Completely Randomized Design
  • B. Randomized Block Design
  • C. Latin Square Design
  • D. Split Plot Design

Answer: C. Latin Square Design

Explanation: Latin Square Design controls variation in both row and column directions simultaneously.

9. Which bacterial genus is widely used as a phosphate-solubilizing biofertilizer?

  • A. Rhizobium
  • B. Azotobacter
  • C. Pseudomonas
  • D. Frankia

Answer: C. Pseudomonas

Explanation: Several Pseudomonas species efficiently solubilize insoluble phosphates by producing organic acids.

10. Which plant growth regulator is commercially used to induce parthenocarpic fruit development in tomato?

  • A. Ethylene
  • B. Gibberellic acid (GA₃)
  • C. Abscisic acid
  • D. Cytokinin

Answer: B. Gibberellic acid (GA₃)

Explanation: GA₃ stimulates fruit development without fertilization, producing seedless (parthenocarpic) tomato fruits.