AQA GCSE Biology Paper 1 Practice Exam 2026 – Complete Study Guide

Maintaining a low concentration gradient outside the leaf facilitates transpiration by speeding up the diffusion of water vapor from inside the leaf to the outside environment. Transpiration is the process by which water vapor exits the leaf through tiny openings called stomata. When the concentration of water vapor inside the leaf is high compared to the concentration in the outside air (which is lower), water vapor diffuses out of the leaf more readily.

A low concentration outside the leaf creates an environment where there is a strong driving force for water vapor to move from an area of higher concentration (inside the leaf) to an area of lower concentration (outside). This is consistent with the principles of diffusion, where substances naturally move from regions of high concentration to regions of low concentration until equilibrium is reached. Therefore, maintaining a low concentration gradient outside the leaf ensures that diffusion occurs efficiently, enhancing the transpiration process, which is crucial for plant hydration and nutrient transport.