Rate of plant growth MCQs With Answer

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Rate of plant growth MCQs With Answer provide B. Pharm students a focused way to master concepts of plant growth analysis, including plant growth rate, AGR, RGR, NAR, CGR, leaf area index and effects of photosynthesis and plant hormones. This Student-friendly guide covers calculation formulas, experimental methods, growth curve interpretation, and factors affecting biomass accumulation and secondary metabolite production—critical for pharmacognosy and drug plant cultivation. Clear questions emphasize RGR formula, units, sink-source relations, and practical measurement techniques to strengthen problem-solving skills for lab and exam settings. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the formula for Relative Growth Rate (RGR)?

  • (W2 – W1) / (t2 – t1)
  • (ln W2 – ln W1) / (t2 – t1)
  • (W2 / W1) / (t2 – t1)
  • (W2 – W1) / W1

Correct Answer: (ln W2 – ln W1) / (t2 – t1)

Q2. Absolute Growth Rate (AGR) is best expressed as:

  • g day^-1
  • mg g^-1 day^-1
  • cm^2 g^-1
  • dimensionless

Correct Answer: g day^-1

Q3. Which parameter measures biomass gain per unit leaf area per unit time?

  • Relative Growth Rate (RGR)
  • Net Assimilation Rate (NAR)
  • Leaf Area Index (LAI)
  • Harvest Index (HI)

Correct Answer: Net Assimilation Rate (NAR)

Q4. If plant dry weight increases from 2 g to 8 g in 4 days, what is the AGR? (Use g day^-1)

  • 1.5 g day^-1
  • 2 g day^-1
  • 0.5 g day^-1
  • 4 g day^-1

Correct Answer: 1.5 g day^-1

Q5. Given W1=1 g, W2=2 g over 2 days, RGR = (ln2 – ln1)/2. What is RGR (approx)?

  • 0.347 day^-1
  • 0.693 day^-1
  • 0.173 day^-1
  • 1.000 day^-1

Correct Answer: 0.347 day^-1

Q6. Which growth curve is typical for most plants over their life cycle?

  • Linear growth curve
  • Exponential growth curve only
  • S-shaped (sigmoid) growth curve
  • Logarithmic decay curve

Correct Answer: S-shaped (sigmoid) growth curve

Q7. Leaf Area Index (LAI) is defined as:

  • Leaf area per unit ground area
  • Leaf dry mass per leaf area
  • Leaf area per plant
  • Number of leaves per plant

Correct Answer: Leaf area per unit ground area

Q8. Net Assimilation Rate (NAR) units are typically:

  • g m^-2 day^-1
  • g g^-1 day^-1
  • g cm^-2 day^-1
  • dimensionless

Correct Answer: g m^-2 day^-1

Q9. Which hormone primarily promotes cell elongation and stem growth?

  • Auxin
  • Abscisic acid
  • Ethylene
  • Salicylic acid

Correct Answer: Auxin

Q10. Specific Leaf Weight (SLW) is the inverse of:

  • Leaf Area Index
  • Leaf Area Ratio (LAR)
  • Specific Leaf Area (SLA)
  • Harvest Index

Correct Answer: Specific Leaf Area (SLA)

Q11. Which factor does NOT directly affect the rate of plant growth?

  • Light intensity
  • Soil water availability
  • Atmospheric CO2 concentration
  • Astrological sign of the planter

Correct Answer: Astrological sign of the planter

Q12. Crop Growth Rate (CGR) is usually expressed per unit:

  • Leaf area
  • Ground area
  • Plant height
  • Root length

Correct Answer: Ground area

Q13. Which measurement is most appropriate for comparing growth between species of different sizes?

  • Absolute Growth Rate (AGR)
  • Relative Growth Rate (RGR)
  • Total biomass only
  • Number of branches

Correct Answer: Relative Growth Rate (RGR)

Q14. RGR has highest values during which growth phase?

  • Mature phase
  • Senescence phase
  • Exponential (log) phase
  • Dormant phase

Correct Answer: Exponential (log) phase

Q15. The term “sink” in plant growth refers to:

  • Photosynthetic leaves
  • Sites of net carbon consumption like roots or fruits
  • Water evaporation sites
  • Places of stomatal opening

Correct Answer: Sites of net carbon consumption like roots or fruits

Q16. Which process reduces net growth by consuming assimilates?

  • Photosynthesis
  • Respiration
  • Transpiration
  • Nitrogen fixation

Correct Answer: Respiration

Q17. For growth analysis, dry weight is preferred over fresh weight because:

  • Dry weight includes water content variation
  • Fresh weight is easier to measure
  • Dry weight removes variation due to water content
  • Fresh weight is constant across samples

Correct Answer: Dry weight removes variation due to water content

Q18. Leaf Area Ratio (LAR) equals:

  • Leaf area / plant dry mass
  • Plant dry mass / leaf area
  • Leaf dry mass / total dry mass
  • Leaf area per ground area

Correct Answer: Leaf area / plant dry mass

Q19. Which statistic is most useful to quantify daily increase in population biomass of a crop stand?

  • AGR per plant
  • CGR per ground area
  • Leaf number increase
  • Root length increment

Correct Answer: CGR per ground area

Q20. If W1=5 g, W2=10 g over 5 days, RGR = (ln10-ln5)/5. What is approximate RGR?

  • 0.139 day^-1
  • 0.693 day^-1
  • 0.301 day^-1
  • 0.446 day^-1

Correct Answer: 0.139 day^-1

Q21. Secondary metabolites often accumulate when growth rate is:

  • Maximized due to abundant nutrients
  • Reduced under stress conditions
  • Unrelated to primary metabolism
  • Only during seedling stage

Correct Answer: Reduced under stress conditions

Q22. Which hormone is primarily involved in promoting cell division in shoots and roots?

  • Cytokinin
  • Ethylene
  • Abscisic acid
  • Gibberellin

Correct Answer: Cytokinin

Q23. The unit of Specific Leaf Area (SLA) is typically:

  • cm^2 g^-1
  • g cm^-2
  • m day^-1
  • g g^-1

Correct Answer: cm^2 g^-1

Q24. Which experimental factor must be standardized when comparing RGR between treatments?

  • Initial plant size
  • Time of measurement
  • Environmental conditions
  • All of the above

Correct Answer: All of the above

Q25. During the lag phase of growth curve, RGR is typically:

  • Highest
  • Zero or low
  • Negative
  • Constant and maximal

Correct Answer: Zero or low

Q26. Which describes the compensation point?

  • Light intensity where photosynthesis equals respiration
  • Point when growth rate becomes infinite
  • Maximum biomass accumulation rate
  • Time when leaves fall

Correct Answer: Light intensity where photosynthesis equals respiration

Q27. In growth analysis, why log-transformation (lnW) is used for RGR?

  • To linearize exponential growth for slope estimation
  • To make units cancel out
  • Because weights cannot be subtracted
  • To increase numerical values

Correct Answer: To linearize exponential growth for slope estimation

Q28. Which nutrient deficiency commonly limits rate of plant growth globally?

  • Iron
  • Nitrogen
  • Copper
  • Chlorine

Correct Answer: Nitrogen

Q29. Harvest Index (HI) is defined as:

  • Ratio of root mass to shoot mass
  • Grain or economically useful yield / total above-ground biomass
  • Leaf area per plant
  • Root length per plant

Correct Answer: Grain or economically useful yield / total above-ground biomass

Q30. Which measurement directly estimates photosynthetic capacity relating to growth?

  • Net assimilation rate (NAR)
  • Specific Leaf Area (SLA)
  • Leaf Area Ratio (LAR)
  • Harvest index

Correct Answer: Net assimilation rate (NAR)

Q31. Which is a common method to measure leaf area for growth analysis?

  • Leaf area meter or image analysis
  • Estimating by eye
  • Counting stomata
  • Measuring root mass

Correct Answer: Leaf area meter or image analysis

Q32. Which statement about exponential growth is true?

  • Absolute growth rate is constant
  • Relative growth rate is constant
  • Mass decreases over time
  • Applies only to animals

Correct Answer: Relative growth rate is constant

Q33. A low RGR but high AGR situation could indicate:

  • Small plant with fast relative increase
  • Large plant with substantial absolute gain
  • Measurement error only
  • No growth occurring

Correct Answer: Large plant with substantial absolute gain

Q34. Which environmental stress typically reduces RGR by limiting photosynthesis?

  • High light intensity
  • Drought stress
  • Optimal temperature
  • Excessive fertilization

Correct Answer: Drought stress

Q35. The primary substrate for growth is:

  • Water alone
  • Carbon fixed by photosynthesis
  • Atmospheric nitrogen exclusively
  • Soil microbes only

Correct Answer: Carbon fixed by photosynthesis

Q36. Which of the following increases sink strength and can enhance growth of targeted organs?

  • Pruning or fruit thinning
  • Lowering temperature drastically
  • Removing fertilizers
  • Blocking phloem transport

Correct Answer: Pruning or fruit thinning

Q37. Which index relates leaf area to plant dry mass and influences RGR?

  • Leaf Area Ratio (LAR)
  • Fruit to leaf ratio
  • Stem thickness index
  • Root density index

Correct Answer: Leaf Area Ratio (LAR)

Q38. Which plant hormone commonly inhibits growth and promotes stomatal closure under stress?

  • Gibberellin
  • Abscisic acid (ABA)
  • Cytokinin
  • Auxin

Correct Answer: Abscisic acid (ABA)

Q39. Which term describes allocation of carbon to roots vs shoots affecting growth trade-offs?

  • Biotic potential
  • Biomass partitioning
  • Photorespiration
  • Evapotranspiration

Correct Answer: Biomass partitioning

Q40. If SLA increases, what is expected effect on LAR (assuming leaf mass fraction constant)?

  • LAR decreases
  • LAR increases
  • No change in LAR
  • LAI becomes zero

Correct Answer: LAR increases

Q41. Which of these best describes “growth analysis” in plant science?

  • Measuring only root lengths
  • Quantitative study of biomass accumulation and its components over time
  • Classifying plant species by appearance
  • Studying insect-plant interactions

Correct Answer: Quantitative study of biomass accumulation and its components over time

Q42. Which factor increases photosynthetic rate and thus can increase growth until saturation?

  • Increasing CO2 concentration
  • Decreasing light intensity to zero
  • Reducing leaf area drastically
  • Removing chlorophyll

Correct Answer: Increasing CO2 concentration

Q43. Which would you monitor to estimate nocturnal carbon loss affecting daily growth?

  • Daytime photosynthesis only
  • Dark respiration rate
  • Soil pH alone
  • Leaf color only

Correct Answer: Dark respiration rate

Q44. An increase in NAR while SLA decreases could indicate:

  • Thicker leaves with higher photosynthetic efficiency
  • Leaves becoming thinner and less efficient
  • Complete cessation of growth
  • Loss of chloroplasts

Correct Answer: Thicker leaves with higher photosynthetic efficiency

Q45. Which measurement helps determine biomass allocation to reproductive organs affecting yield?

  • Leaf Area Index (LAI)
  • Harvest Index (HI)
  • Specific Leaf Area (SLA)
  • Root:shoot ratio only

Correct Answer: Harvest Index (HI)

Q46. Which is TRUE about plant growth under low temperatures?

  • Enzymatic activity decreases slowing growth
  • Photosynthetic enzymes become hyperactive
  • Respiration increases dramatically promoting growth
  • Water uptake becomes unlimited

Correct Answer: Enzymatic activity decreases slowing growth

Q47. When comparing treatments, which statistical approach is essential for reliable growth comparison?

  • Replication and randomized design
  • Single replicate without controls
  • Changing multiple variables simultaneously
  • Ignoring variance

Correct Answer: Replication and randomized design

Q48. Which growth metric would be most sensitive to short-term diurnal changes?

  • Harvest Index
  • Leaf water content and turgor-linked fresh weight
  • Long-term RGR over months
  • Seed yield after harvest

Correct Answer: Leaf water content and turgor-linked fresh weight

Q49. Photorespiration typically reduces net photosynthetic gain by:

  • Enhancing carbon fixation efficiency
  • Consuming O2 without producing sugars, reducing net gain
  • Increasing RGR directly
  • Converting all carbohydrates to proteins

Correct Answer: Consuming O2 without producing sugars, reducing net gain

Q50. In designing a growth experiment for medicinal plants, which is critical to report for reproducibility?

  • Environmental conditions, sampling intervals, and measurement methods
  • Only final yield without methods
  • Seed supplier exclusively
  • Color of the pots

Correct Answer: Environmental conditions, sampling intervals, and measurement methods

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