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A student used a potometer to measure the rate of water uptake by a leafy shoot. The air bubble moved 45 mm along a capillary tube of radius 0.5 mm in 5 minutes.
Volume of a cylinder = π r2 × length
Calculate the rate of water uptake, in mm3 min-1.
Explain why a potometer measures the rate of water uptake rather than the rate of transpiration exactly.
State one variable that should be kept constant during this investigation.