Agronomy Crop Physiology 1 — Questions and Answers
Question 1: What is the primary pigment responsible for capturing light energy during photosynthesis?
- Carotenoid
- Chlorophyll a (Correct answer)
- Phycocyanin
- Anthocyanin
Correct answer: Chlorophyll a
Chlorophyll a is the primary photosynthetic pigment that directly participates in the light reactions by absorbing and transferring light energy.
Question 2: Which process describes the loss of water vapor from plant leaves primarily through stomata?
- Guttation
- Osmosis
- Transpiration (Correct answer)
- Imbibition
Correct answer: Transpiration
Transpiration is the evaporation of water from plant surfaces through stomata, which creates a water potential gradient that drives water uptake from the soil.
Question 3: What is photorespiration in crop plants?
- Photosynthesis that occurs during respiration
- Light-dependent ATP production in mitochondria
- A wasteful process where RuBisCO fixes O2 instead of CO2 (Correct answer)
- Cellular respiration that is accelerated by light
Correct answer: A wasteful process where RuBisCO fixes O2 instead of CO2
Photorespiration occurs when RuBisCO binds oxygen instead of CO2, releasing previously fixed carbon as CO2 without producing useful sugars, reducing yield.
Question 4: Which photosynthetic pathway do corn (maize) and sugarcane use to efficiently fix carbon in hot climates?
- C3 pathway
- CAM pathway
- C4 pathway (Correct answer)
- C2 pathway
Correct answer: C4 pathway
Corn and sugarcane use the C4 pathway, which spatially concentrates CO2 in bundle sheath cells to minimize photorespiration and improve photosynthetic efficiency.
Question 5: Which plant hormone is the primary driver of fruit ripening and is produced as a gas?
- Cytokinin
- Ethylene (Correct answer)
- Gibberellin
- Auxin
Correct answer: Ethylene
Ethylene is the gaseous plant hormone responsible for accelerating fruit ripening, leaf abscission, and other senescence processes in harvested crops.
Question 6: What does the Calvin Cycle (light-independent reactions) primarily produce?
- ATP
- NADPH
- Oxygen
- Glyceraldehyde-3-phosphate (G3P) (Correct answer)
Correct answer: Glyceraldehyde-3-phosphate (G3P)
The Calvin Cycle uses ATP and NADPH from the light reactions to fix CO2 into glyceraldehyde-3-phosphate (G3P), which serves as the building block for glucose.
Question 7: What is the net ATP yield per glucose molecule during complete aerobic cellular respiration?
- 2 ATP
- 8 ATP
- 36–38 ATP (Correct answer)
- 20 ATP
Correct answer: 36–38 ATP
Complete aerobic respiration of one glucose molecule yields approximately 36–38 ATP through glycolysis, the Krebs cycle, and oxidative phosphorylation via the electron transport chain.
Agronomy Crop Physiology 1
What is the primary pigment responsible for capturing light energy during photosynthesis?