Opposing requirements
Gas exchange requires stomata to connect the internal air spaces of a leaf with the atmosphere. When these pores are open, however, water vapour can also leave the plant.
Plants in dry conditions therefore face opposing demands: stomata must permit gas exchange while excessive water loss needs to be avoided.
| Requirement | Consequence |
|---|---|
| Gas exchange | Open stomata allow gases to pass between the atmosphere and the internal air spaces. |
| Water conservation | Reducing the number or exposure of routes for evaporation limits water loss. |
Plants with structural adaptations that conserve water under conditions of limited water availability are described as xerophytic.