Humidity
/hjuˈmɪdəti/
Definition
Humidity is the amount of water vapor in the air around a plant, usually discussed as relative humidity, the percentage of moisture the air holds compared with the maximum it could hold at that temperature. It describes an environmental condition, not water in the soil. Humidity affects transpiration, the loss of water from leaves through stomata, and influences how quickly foliage dries and how some plants function.
Role and Significance
- Leaf water balance: Humidity strongly affects how quickly leaves lose water through transpiration, the movement of water vapor out of tiny pores called stomata. Low humidity can increase water loss, while very high levels can slow it.
- Stomata and nutrient flow: Because transpiration helps pull water and dissolved minerals upward from the roots, humidity can influence nutrient movement through the plant. This is one reason dry indoor air can stress some houseplants even when soil moisture is adequate.
- Disease pressure indoors and outdoors: High humidity around foliage can favor many fungal and bacterial problems, especially where air circulation is poor. Crowded plants and wet leaf surfaces often make these conditions more serious.
- Propagation and tropical species: Cuttings and many tropical plants often perform better in higher humidity because they lose water faster than they can replace it. Growers use domes, enclosed trays, or greenhouses to reduce moisture loss during rooting.
Related Terms
Transpiration
Transpiration is the plant process of losing water vapor to the air, mainly through tiny leaf pores called stomata, and…
Stoma
Stoma refers to a microscopic pore in the epidermis, the outer cell layer of leaves and young stems. Each stoma is…
Guard cell
Guard cell refers to one of the two specialized plant epidermal cells that surround a stoma, the tiny pore on a leaf or…
Watering
Watering is the horticultural practice of applying water to soil or growing media around plants, or less often directly…
Overwatering
Overwatering describes a condition in which soil stays wet for too long or is watered more often than roots can use. In…
Underwatering
Underwatering describes a condition in which a plant receives less water than it needs to maintain normal growth and…