1. Which enzyme catalyzes the oxygenation reaction of RuBP during photorespiration?

  • A. Phosphoenolpyruvate carboxylase
  • B. Rubisco
  • C. Carbonic anhydrase
  • D. Ribulose phosphate epimerase

Answer: B. Rubisco

Explanation: Rubisco possesses both carboxylase and oxygenase activities. Under low CO₂ and high O₂ conditions, it oxygenates RuBP, initiating photorespiration.

2. Which of the following soil phosphorus fractions is considered immediately available to plants?

  • A. Occluded phosphorus
  • B. Organic phosphorus
  • C. Soil solution phosphorus
  • D. Mineral phosphorus in apatite

Answer: C. Soil solution phosphorus

Explanation: Plants absorb phosphorus mainly as H₂PO₄⁻ and HPO₄²⁻ ions present in the soil solution.

3. In quantitative genetics, the average superiority of F₁ hybrids over the mid-parent value is known as:

  • A. Inbreeding depression
  • B. Heterosis
  • C. Epistasis
  • D. Genetic drift

Answer: B. Heterosis

Explanation: Heterosis or hybrid vigor refers to the superior performance of F₁ hybrids compared to the average of their parents.

4. Which bacterium is responsible for crown gall disease in dicotyledonous plants?

  • A. Xanthomonas campestris
  • B. Agrobacterium tumefaciens
  • C. Erwinia amylovora
  • D. Pseudomonas syringae

Answer: B. Agrobacterium tumefaciens

Explanation: Agrobacterium tumefaciens causes crown gall disease by transferring T-DNA from its Ti plasmid into plant cells.

5. Which statistical test is commonly used to compare the means of more than two treatments in agricultural experiments?

  • A. Chi-square test
  • B. t-test
  • C. Analysis of Variance (ANOVA)
  • D. Regression analysis

Answer: C. Analysis of Variance (ANOVA)

Explanation: ANOVA determines whether significant differences exist among the means of three or more treatments.

6. Which hormone promotes stomatal closure during drought stress?

  • A. Auxin
  • B. Cytokinin
  • C. Abscisic acid
  • D. Gibberellin

Answer: C. Abscisic acid

Explanation: Abscisic acid accumulates during water stress and induces stomatal closure, thereby reducing transpiration.

7. Which disease of pearl millet is caused by Sclerospora graminicola?

  • A. Ergot
  • B. Rust
  • C. Downy mildew
  • D. Smut

Answer: C. Downy mildew

Explanation: Downy mildew of pearl millet is caused by Sclerospora graminicola and is one of its most destructive diseases.

8. The movement of water from soil into roots occurs primarily due to differences in:

  • A. Temperature
  • B. Osmotic pressure
  • C. Water potential
  • D. Atmospheric pressure

Answer: C. Water potential

Explanation: Water moves from regions of higher water potential to lower water potential through the soil-plant-atmosphere continuum.

9. Which breeding system involves intermating selected superior individuals for several cycles to accumulate favorable alleles?

  • A. Mutation breeding
  • B. Recurrent selection
  • C. Pure line selection
  • D. Backcross breeding

Answer: B. Recurrent selection

Explanation: Recurrent selection repeatedly selects and intermates superior individuals to improve populations, especially in cross-pollinated crops.

10. Which of the following is the principal storage polysaccharide in higher plants?

  • A. Cellulose
  • B. Glycogen
  • C. Chitin
  • D. Starch

Answer: D. Starch

Explanation: Starch, composed of amylose and amylopectin, is the major storage carbohydrate in higher plants.