Capillary action
/kəˈpɪləri ˈækʃən/
Definition
Capillary action is a physical process in which water moves through narrow spaces because the water molecules stick to nearby surfaces and pull on each other. In plants, this helps water rise through tiny cell walls and xylem tissues, especially in fine roots and stems. It is not driven by pumping; it depends on adhesion, cohesion, and the small diameter of the spaces the water moves through.
Biological Role
- Water movement in xylem: In stems, capillary action helps water enter and move through xylem, the water-conducting tissue. It supports the upward pull created by transpiration, which is water loss from leaves.
- Moisture spread in growing media: In potting mixes and seed-starting trays, capillary action draws water through small spaces between particles. This is why bottom watering can moisten a container from the drainage holes upward.
- Limits in tall plants: Capillary action contributes only part of the rise needed in large plants. Trees depend mainly on cohesion-tension, the pull created when water molecules stick together and evaporate from leaves.
Related Terms
Capillary
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Wicking
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Bottom watering
Bottom watering refers to a watering technique in which a pot is placed in shallow water so moisture moves upward…
Self-watering pot
Self-watering pot refers to a container designed for growing plants with a built-in water reservoir below the root…
Watering
Watering is the horticultural practice of applying water to soil or growing media around plants, or less often directly…
Drainage
Drainage describes how quickly excess water moves out of soil or a potting mix after watering or rain. In horticulture…
Osmosis
Osmosis is a biological process in which water moves across a selectively permeable membrane, such as a plant cell…
Soil
Soil is the natural surface layer of land where most plants root and grow. It is a living mixture of mineral particles…