Weather affects response, dry conditions for example, decreasing the effects because of lower stomatal conductance.
Occlusion may lead to increased resistance to gas exchange, or may prevent full stomatal closure, leading to water stress.
We would normally expect stomatal density to be related to the climate in which the plant is adapted to grow.
However, water vapor also escapes when stomata are open and plants must therefore control stomatal opening to prevent excess water loss.
Recent work has shown that ABA and pH signals can combine even in very mildly stressed plants to regulate stomatal behavior and water loss.