An agricultural scientist investigated the effect of relative humidity on the stomatal pore width in the leaves of a crop plant (Zea mays) cultivated inside a growth chamber with constant temperature and light intensity.
| Relative humidity (%) | Average width of stomatal pore (μm\mu\text{m}μm) |
|---|---|
| 90 | 8.8 |
| 75 | 8.4 |
| 60 | 5.2 |
| 45 | 2.5 |
| 30 | 0.9 |
Using the data in the table, explain why the change in relative humidity from 75% to 30% affected the width of the stomatal pore.
