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Plant Organ Systems
The roots, stem and leaves form a plant organ system for TRANSPORT OF SUBSTANCES around the plant. Here are examples of different structures within plants and how they're adapted to perform their functions:
1. Phloem Tubes
- Transports SUGAR and other FOOD SUBSTANCES in the form of CELL SAP around the plant.
- They are made of ELONGATED LIVING CELLS that are joined together to create a continuous tube.
- Cell sap can move from one phloem cell to the next through PORES in the end walls.
- The sugar and nutrients can travel in BOTH DIRECTIONS of the phloem.
- The process where sugar and nutrients move through the phloem is called TRANSLOCATION.
2. Xylem Tubes
- Transports WATER and MINERALS from the roots to the leaves.
- They are made of DEAD CELLS that form continuous tubes and are strengthened by a substance known as LIGNIN.
- The xylem is completely HOLLOW
- The water and minerals can only move in ONE DIRECTION up the plant from the roots to the leaves.
- The route that the xylem takes is known as the TRANSPIRATION STREAM.
3. Root Hair Cells:
- Found in the ROOTS and are specialised for ABSORBING WATER AND MINERALS.
- Water is taken in by OSMOSIS and minerals are taken in by ACTIVE TRANSPORT.
- They grow long "hairs" to INCREASE SURFACE AREA for absorption from the soil.
4. Stomata
Stomata are small openings on the underside of leaves, regulated by GUARD CELLS:
- In the day time when light intensity is HIGH, the guard cells become TURGID (full of water) and they OPEN the stomata. This is because more PHOTOSYNTHESIS occurs in the daytime which means more CARBON DIOXIDE needs to be taken in. This also results in the release of more WATER and OXYGEN.
- In the night time, the light intesity is LOW and the guard cells become FLACCID (less water). This means the stomata CLOSE as less PHOTOSYNTHESIS occurs. This prevents the loss of excess WATER.
Plant Organ Systems
The roots, stem and leaves form a plant organ system for TRANSPORT OF SUBSTANCES around the plant. Here are examples of different structures within plants and how they're adapted to perform their functions:
1. Phloem Tubes
- Transports SUGAR and other FOOD SUBSTANCES in the form of CELL SAP around the plant.
- They are made of ELONGATED LIVING CELLS that are joined together to create a continuous tube.
- Cell sap can move from one phloem cell to the next through PORES in the end walls.
- The sugar and nutrients can travel in BOTH DIRECTIONS of the phloem.
- The process where sugar and nutrients move through the phloem is called TRANSLOCATION.
2. Xylem Tubes
- Transports WATER and MINERALS from the roots to the leaves.
- They are made of DEAD CELLS that form continuous tubes and are strengthened by a substance known as LIGNIN.
- The xylem is completely HOLLOW
- The water and minerals can only move in ONE DIRECTION up the plant from the roots to the leaves.
- The route that the xylem takes is known as the TRANSPIRATION STREAM.
3. Root Hair Cells:
- Found in the ROOTS and are specialised for ABSORBING WATER AND MINERALS.
- Water is taken in by OSMOSIS and minerals are taken in by ACTIVE TRANSPORT.
- They grow long "hairs" to INCREASE SURFACE AREA for absorption from the soil.
4. Stomata
Stomata are small openings on the underside of leaves, regulated by GUARD CELLS:
- In the day time when light intensity is HIGH, the guard cells become TURGID (full of water) and they OPEN the stomata. This is because more PHOTOSYNTHESIS occurs in the daytime which means more CARBON DIOXIDE needs to be taken in. This also results in the release of more WATER and OXYGEN.
- In the night time, the light intesity is LOW and the guard cells become FLACCID (less water). This means the stomata CLOSE as less PHOTOSYNTHESIS occurs. This prevents the loss of excess WATER.
