CHT Plant Physiology & Growth 2 — Questions and Answers
Question 1: Photoperiodism refers to a plant's response to:
- The intensity of light during the day
- The relative lengths of day and night (Correct answer)
- The wavelength of light used for photosynthesis
- The direction of light source
Correct answer: The relative lengths of day and night
Photoperiodism is the physiological response to the duration of light and dark periods, controlling flowering time in many species.
Question 2: Which plant hormone is most associated with fruit ripening and senescence?
- Gibberellin
- Cytokinin
- Ethylene (Correct answer)
- Brassinolide
Correct answer: Ethylene
Ethylene is a gaseous hormone that triggers fruit ripening, leaf abscission, and flower senescence.
Question 3: What is the primary function of the phloem in vascular plants?
- Transport of water from roots to leaves
- Transport of mineral nutrients from soil into roots
- Transport of photosynthates (sugars) from leaves to other plant parts (Correct answer)
- Structural support of stems and branches
Correct answer: Transport of photosynthates (sugars) from leaves to other plant parts
Phloem conducts sugars and other organic compounds produced during photosynthesis from source tissues (leaves) to sink tissues (roots, fruits).
Question 4: A plant showing interveinal chlorosis on young leaves (veins remain green, tissue between yellows) most likely has a deficiency of:
- Nitrogen
- Phosphorus
- Iron or Manganese (Correct answer)
- Calcium
Correct answer: Iron or Manganese
Iron and manganese are immobile nutrients needed for chlorophyll synthesis; deficiency appears first on young leaves with green veins and yellow tissue between them.
Question 5: Turgor pressure in plant cells is caused by:
- The weight of cytoplasm pushing against the cell wall
- Water entering the vacuole via osmosis, pushing against the cell wall (Correct answer)
- Cellulose microfibrils expanding under light exposure
- ATP-driven pumps inflating the central vacuole
Correct answer: Water entering the vacuole via osmosis, pushing against the cell wall
When water enters the central vacuole by osmosis, it creates turgor pressure that keeps non-woody plant cells rigid and maintains wilting resistance.
Question 6: C4 plants are better adapted to hot, sunny environments than C3 plants because they:
- Fix CO2 using a 3-carbon intermediate that is more stable at high temperatures
- Concentrate CO2 around Rubisco, reducing photorespiration (Correct answer)
- Open stomata at night to reduce water loss via CAM photosynthesis
- Produce higher levels of ethylene to reduce leaf temperature
Correct answer: Concentrate CO2 around Rubisco, reducing photorespiration
C4 plants use a CO2-concentrating mechanism that delivers CO2 directly to Rubisco in bundle sheath cells, greatly reducing energy-wasting photorespiration.
Question 7: What is vernalization?
- Treating seeds with fungicide before planting
- The process of hardening off transplants to outdoor conditions
- Exposure to prolonged cold that triggers flowering in certain plants (Correct answer)
- Applying growth regulators to induce dormancy before winter
Correct answer: Exposure to prolonged cold that triggers flowering in certain plants
Vernalization is the induction of flowering by a prolonged period of cold, ensuring that plants like winter wheat or biennial crops flower only after winter.
CHT Plant Physiology & Growth 2
Photoperiodism refers to a plant's response to: