Potometer measures water uptake volume per time as transpiration proxy

Steps:

• Identify potometer function: measures rate of water absorption by plant shoot, indicating transpiration.
• Note measurement method: volume of water entering capillary tube over time, via meniscus or bubble displacement adjusted by tube area.
• Calculate rate: volume = distance × cross-sectional area; rate = volume / time.
• Determine units: volume in cm³, time in min, so cm³ min⁻¹.

Why B is correct:

• Transpiration rate is the volume of water vapor lost per unit time, and potometer quantifies this via water uptake volume per time (cm³ min⁻¹).

Why the others are wrong:

• A: Measures linear speed of meniscus (cm min⁻¹), not volume-based rate.
• C: Represents area change per time (cm² min⁻¹), unrelated to water volume.
• D: Indicates acceleration (cm min⁻²), not a steady rate.

Final answer: B