Garden with Insight v1.0 Help: vapor pressure

Vapor pressure is the partial pressure of water vapor in the air, which is the pressure exerted by water molecules in the air on a liquid in contact with the air (such as water). The vapor pressure is equal to the relative humidity (as a proportion) times the saturation vapor pressure, which is how much water vapor the air can hold. Vapor pressure affects evaporation (because water is less likely to evaporate when there is more water vapor in the air) which in turn affects plant transpiration and photosynthesis.