All plants inhale carbon dioxide through their leaves. This gas is used in photosynthesis. As the plant opens its leaf pores to take in carbon dioxide, some of the moisture in the leaf can escape. Thus the plants sweat water vapor into the air whenever they breath.
Dry air causes plants to transpire moisture much more rapidly than does humid air. Water
The important point to remember is that dry air pulls water out of the leaves faster than the
When plants have the right humidity they thrive, because they open their pores completely and so breath deeply without threat of excessive water loss. When the air is moist, there is little water lost from the leaf. Damping down the benches and surrounds, also misting leaves will keep the air moist. Rapid temperature rises damage orchids too. It means that
Under these conditions, photosynthesis, transpiration and the other vital plant processes, are severely restricted and as a result, developing flower growth and new growth are damaged. Rapid rises in temperature on sunny days can be avoided by opening vents or doors early in the morning - and letting the greenhouse warm gradually.
A humid atmosphere that is not moving, is particularly undesirable also. Damp, stagnant conditions encourage mould and bacterial diseases. A constantly moving, light and buoyant atmosphere keeps orchids vigorous and healthy.