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PLANT SUPPORT - Coggle Diagram
PLANT SUPPORT
TERRESTRIAL PLANTS
- Faces problems of gravitational pull when it spreads its leaves horizontally to absorb maximum sunlight.
Woody plants: Sclerenchyma tissue
- Support is provided by sclerenchyma and xylem tissues.
- Sclerenchyma tissues composed of secondary cell wall which are usually lignified. it support non-growing parts of plants because they have thick, rigid, non-stretchable cell walls.
Types: Fibres and Sclereids
- Fibres: long, straight & thin / found in vascular tissues.
- Sclereids: Short, circular, irregular-shaped / found in fruits & seeds.
Terrestrial plants
- Support: Provided by turgidity of parenchyma and collenchyma cells.
- Turgor pressure of fluids in centre vacuole pushes cell content and plasma membrane against cell walls, creating support for stems, roots and leaves.
- Cellulose and pectin in collenchyma cells thickened the cell walls to provide additional strength
- Example: spinach and balsam
Woody plants: xylem vessels
- Early development, cell wall of xylem and tracheids are thickened with lignin results in different types of vessels.
- Types of vessels: annular vessels, spiral vessels, scalariform vessels and pitted vessels. These are primary vessels.
- As plant grow, they undergo secondary growth resulting in formation of secondary xylem called wood.
- Wood makes plant stronger and provides mechanical support.
AQUATIC PLANTS
- Have less support-related problems because water provides buoyancy and support and effect of gravity are minimal
AQUATIC PLANTS
Submerged plants:
- Thin, narrow and flexible leaves to provide little resistance to water flow.
- Air sacs within leaves and stems could keep the plants afloat close to the sufface for absorption of sunlight,
- Water buoyancy provides support as their stems have no woody tissue.
- Example: Hydrilla sp., elodea, pondweed and eelgrass.
AQUATIC PLANTS
Floating plants:
- Have broad leaves that are firm but flexible to resist being torn.
- Have aerenchyma tissues in stems and leaves
- Aerenchyma tissue: spongy tissues with large air spaces between cells. They provide buoyancy so that plants can float.
- Example: water hyacinth, duckweed
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