The
Affects of
Humidity on
Plants. ... As
plants transpire, the
humidity around saturates leaves with water vapor. When relative
humidity levels are too
high or there is a lack of air circulation, a
plant cannot make water evaporate (part of the transpiration process) or draw nutrients from the soil.
Climate control for plant growth is an essential consideration in regards to pest and disease management. When conditions are too humid, it may promote the growth of mold and bacteria that cause plants to die and crops to fail, as well as conditions like root or crown rot. Humid conditions also invite the presence of pests, such as fungus gnats, whose larva feed on plant roots and thrive in moist soil.
https://www.polygongroup.com/en-US/blog/how-humidity-affects-the-growth-of-plants/