A student investigated the effect of air movement on the rate of transpiration in a leafy shoot using a potometer.
Initially, the shoot was kept in still air. After 4 minutes, an electric fan was switched on to create a constant breeze.
The table below shows the results of this investigation.
| Time (minutes) | Cumulative volume of water taken up (textmm3\\text{mm}^3textmm3) - Still air throughout | Cumulative volume of water taken up (textmm3\\text{mm}^3textmm3) - Fan switched on after 4 minutes |
|---|---|---|
| 0 | 0 | 0 |
| 2 | 6 | 6 |
| 4 | 12 | 12 |
| 6 | 18 | 26 |
| 8 | 24 | 40 |
| 10 | 30 | 54 |
Explain why switching on the fan caused an increase in the volume of water taken up by the leafy shoot.