Support in plant ( Physiological support & Structural support )
Support in plants
The plant has various methods and systems for support to maintain its shape and for its protection , These methods may be physiological or structural , The physiological support is a temporary support , because it depends on the presence of the water in the plant cells and there is no support , if this water is lost .
The physiological support
Physiological support affects on the the cell itself as a whole .
How does it occur ?
The size and pressure of sap vacuole increase which press in turn on the protoplasm , pushing it to outside towards the wall and that affects on the shape of the cell wall .
The cell wall extends , due to the increase of the pressure acting on it , then the cell swells and becomes with a strained wall to get the support .
- The swelling ( the size increasing ) of dried fruits , on soaking them in the water for a period of time , due to its absorption of the water by osmosis .
- The shrinkage ( wilt ) of fresh seeds as peas or beans , on leaving them for a period of time , due to the loss of the water from their cells .
- The wilting of leaves and stems of herbaceous plants that face soil drought , due to the absence of its cells turgidity , as a result of the loss of water , So , the physiological support disappears .
- The straightness of leaves and stems of herbaceous plants , on irrigating the soil , due to the swelling of their internal tissues cells , as a result of the pressure of water to their vacuoles by osmosis .
The structural support
Structural support affects on the cell wall or some parts of the cell .
How does it occur ?
The deposition of some rigid strong substances on the cell wall or in some of its parts to :
- Increase the ability of external plant cells to protect the internal plant tissues .
- Prevent the loss of the water from the inner cells .
- Acquire the cells the hardness ( turgidity ) and strength ( support the plant ) .
The structural support is a permanent support , because it depends on the deposition of some substances on the plant cell walls or in some of its parts such as cellulose , lignin , suberin and cutin which acquires the plant the turgidity and strength , maintains the internal plant tissues and prevents the loss of the water through them .
- The increase of thickness of epidermal cell walls ( especially the outer cells of it ) .
- Deposition of cutin which is impermeable to the water on the epidermal cell walls .
- Deposition of cellulose or lignin on the plant cell walls or on some of its parts such as the collenchyma cells and sclerenchyma cells ( fibers and stone cells ) to acquire them the turgidity and strength , where the site of presence of these cells and their distribution support the plant .
- The plant may surround itself by an impermeable cork cells layer containing suberin to prevent the loss of the water .