How Plants Support Themselves
Unlike animals, plants have no bones or muscles. They stay upright using other structures. In young, soft (herbaceous) plants, support comes mainly from turgor pressure — the pressure of water inside cells that keeps them firm. When cells are full of water they are turgid and the stem stands straight; when water is lost the plant wilts.
Supporting Tissues
- Xylem — tubes with thick, woody walls that carry water and also give strong support to the stem.
- Sclerenchyma and collenchyma — tissues with thickened walls that strengthen the plant.
- In trees, wood (secondary xylem) provides the main support, allowing them to grow very tall.
Key idea
Soft plants stand up using turgor pressure (water). Woody plants and trees are supported by strong xylem and wood tissue. Loss of turgor causes wilting.
Stability and Roots
Stability means resisting being blown over or uprooted. Plants stay stable through their root system. A deep tap root anchors the plant firmly, while a spreading fibrous root system grips a wide area of soil. Some tall trees also grow buttress roots or prop roots for extra support.
Example
The oil palm, an important crop in Malaysia, has a spreading fibrous root system that anchors the tall trunk against strong tropical winds. A maize plant grows prop roots from its lower stem for the same reason.
Growth in Plants
Plants grow throughout their life at special regions called meristems, found at the tips of roots and shoots. Growth increases the plant's height, root length and number of leaves.
This is why a plant that has not been watered droops during a hot afternoon but often recovers once it takes up water again in the cooler evening. Woody support, unlike turgor, does not depend on water, so a tree stays standing even during a long dry spell.
Remember
Turgor pressure supports soft plants; xylem and wood support woody plants; roots provide stability. A wilting plant has lost turgor pressure.