Zusammenfassung der Ressource
Transport in plants
- Xylem
- Passive transport
- Transport medium
- Water and dissolved inorganic salts.
- Driving mechanism
- Transpiration stream
- Role
- Chemical substances that are needed for photosynthesis e.g water mineral ions, are carried by xylem tissue from the roots (site
of absorption) up to the leaves where they will be used for the manufacture of food (photosynthesis
- Xylem tissue consists of:
- Xylem vessels
- Tracheids
- Fibres
- Parenchyma cells
- Phloem
- Transport medium
- Dissolved sugars (organic nutrients)
- Driving mechanism
- Pressure-flow/translocation
- "Source to sink"
- Active transport
- Process
- Phloem loading involves sugar moving by active transport into the sieve tube
- Water then follows due to osmosis and then transpiration pull draws the water up the stem.
- Cohesion between the water molecules causes the water to form a continuous stream up the plant
and "pulls" the water up.
- Adhesion between the water molecules and the walls of the xylem vessels also helps draw water up the plant
and at night when the flow ceases it prevents back flow.
- Role
- Most photosynthesis occurs in plant leaves. Phloem vessels are involved in the transport of organic nutrient products e.g sugars, amino
acids and plant hormones to all parts of the plant.
- Movement
- Occurs in two directions - up towards the flowers and down to the roots.
- Phloem tissue consists of:
- Phloem fibres
- Phloem parcnchyma
- Sieve cells
- Companion cells
- The role of transport in plants is mainly to carry materials for photosynthesis to the cells and
move cell products away to other parts of the plant.