Calculating transpiration rate from potometer data

Steps:

• Measure distance the air bubble moves in the capillary tube to determine water uptake volume via π r² × distance.
• Use radius of the capillary tube to calculate its cross-sectional area for volume computation.
• Record time taken for the bubble movement to find volume per hour.
• Measure surface area of leaves on the shoot to normalize rate per square meter.

Why C is correct:

• Transpiration rate = (volume of water / time) / leaf area, where volume = π r² × distance moved, matching mm³ m⁻² h⁻¹ units.

Why the others are wrong:

• A: Reservoir volume and tube length are irrelevant; temperature and leaf count do not yield precise area or volume.
• B: Reservoir volume does not measure uptake; bubble distance is needed for accurate volume.
• D: Lacks bubble distance and leaf area; temperature and leaf count are insufficient for rate calculation.

Final answer: C