ABSTRACT
Growth and development are influenced by humidity in and around the plant. Low air humidity creates an environment that enhances the potential for significant plant water loss. At the same time, regulating water loss through stomatal closure causes a reduction in carbon dioxide (CO2) diffusion that limits growth. High air humidity, on the other hand, promotes environmental conditions favorable for disease development. Humidity refers to the amount of water vapor in the atmosphere. Globally, water vapor levels vary from almost zero in the arctic regions of the world to 4 or 5% of the atmospheric volume in the equatorial regions. The percentage of actual vapor in the atmosphere at any given time in relation to the maximum amount of vapor that can be held is termed relative humidity (RH).
