Igcse Model Questions Vol1 2021 Biology Question 37

Two desert shrubs, A and B, differ in leaf morphology and stomatal behaviour. - Leaf surface area: A = 0.02 m², B = 0.015 m². - Cuticular transpiration rate (per unit area): A = 0.8 mg m⁻² h⁻¹, B = 0.5 mg m⁻² h⁻¹. - During the hottest 4 h of the day, shrub A can close its stomata, reducing stomatal transpiration by 60 %; shrub B cannot close its stomata. Assume that when stomata are open, stomatal transpiration adds an amount equal to the cuticular rate. Calculate the total water loss (in mg) over a 24‑hour period for each shrub and state which shrub loses less water. Also compare each loss with that of a non‑adapted plant that has a leaf area of 0.025 m², a cuticular rate of 1.0 mg m⁻² h⁻¹ and no stomatal closure, expressing the percentage reduction in water loss for shrubs A and B relative to the non‑adapted plant.