Mass transport in plants
- Created by: gsemma
- Created on: 14-02-19 09:45
View mindmap
- vascular tissues
- vascular tissues are grouped in vascular bundles which may contain other tissues that can strengthen the bundles.
- water and minerals are transported from the roots to the leaves of the plant in the xylem tissue.
- Sugars produced during photosynthesis are transported around the whole plant in the phloem
- Mass Transport in Plants
- stem
- non-woody plants- vascular bundles are separate and discrete.
- woody plants- bundles form complete ring around he stem under the bark.
- cambium- a layer of meristem found between the xylem and phleom
- roots
- endodermis- envelope around the vascular bundle
- pericycle- layer underneath the endodermis
- Medulla- all tissue in cortex (outer section of root that surrounds endodermis).
- pericycle- layer underneath the endodermis
- endodermis- envelope around the vascular bundle
- leaf
- vascular bundles form the midrib and veins of a leaf ina branching network
- transpiration
- transports minerals up the plant- maintains cell turgidity- evaporation for cooling- water is supplied for growth, division and photosynthesis.
- light intensity
- stomata can only open when light as photosynthesis can only occur when light
- temperature
- high temps. increase rate due to increases KE increasing evaporation from leaves- increasing rate od diffusion through stomata- decreasing water vapour potential of air making more water leave due to conc' grad.
- Humidty
- higher- decreases rate of transpiration due to smaller WP difference between air and leaf.
- Air movement
- decreases humidity therefore increases rate of transpiration.
- Water availability
- if there is not enough water stomata close so slows rate of transpiration.
- Measure rate of transpiration using a potometer.
- the distance the air bubble travels can be used to calculate the volume of water transpired per unit time.
- evidence for transpiration
- ringing experiment- tracer experiment- chemical tests and aphid test.
- evidence against
- not all solutes move at the same rate- the role of sieve plates is unclear.
- translocation
- phloem consists of companion cells and sieve tube elements.
- sieve tube element- elongated tube aligned end to end. has no nucleus and very little cytoplasm. at each end the cells are separated by perforated sieve plates. five or six sided walls.
- companion cells- large nucleus and dense cytoplasm many mitrocondria to create ATP for active transport. connected to the sieve tube element by pores called plasmodesmata.
- 1. Sucrose
is less reactive than glucose so the palisade mesophyll cells convert glucose from photosynthesis into sucrose.
- 2. Sucrose is actively pumped into the phloem via
the compainon cell
- 3. Hydrogen ions are actively
pumped out of the companion cell. They diffuse back via co-transport protein,
carrying with it a sucrose molecule.
- 4. Water
potential in phloem is lowered so water moves into the phloem (sieve tube
element) from the xylem via osmosis
- 5. Hydrostatic pressure increases so sucrose solution is forced downwards- mass flow.
- 4. Water
potential in phloem is lowered so water moves into the phloem (sieve tube
element) from the xylem via osmosis
- 3. Hydrogen ions are actively
pumped out of the companion cell. They diffuse back via co-transport protein,
carrying with it a sucrose molecule.
- Evidence for
- radioactive markers of Carbon therefore sucrose- ringing a tree so it bulges when sucrose builds up- pH of companion cell is higher due to H+ ions- conc' of sucrose in source is higher than sink
- evidence against
- not all solutes move at same rate- sucrose is moved to parts of plant at same rate no matter that conc'- role of sieve plates is unclear.
- 2. Sucrose is actively pumped into the phloem via
the compainon cell
- active and passive process
- sink- where carbs go
- Source- where carbs come from
- image
- phloem consists of companion cells and sieve tube elements.
- water transport in xylem
- dead- lignin strengthens and waterproofs them- no lignin at bordered pits so osmosis can occur. narrow tube prevents air bubbles to maintain transpiration stream
- Lignification kills cells.
- Living parenchyma cells separate and support vessels.
- root pressure- the loading of water into the xylem can push it up the stem a few metres.
- transpiration pull- the loss of water that the leaves drags water up the xylem- water molecules are cohesive so they stick to each other.
- capillairy action- the water also adheres t the walls and sue to the narrow nature of the xylem, the water pulls itself up
- transpiration pull- the loss of water that the leaves drags water up the xylem- water molecules are cohesive so they stick to each other.
- dead- lignin strengthens and waterproofs them- no lignin at bordered pits so osmosis can occur. narrow tube prevents air bubbles to maintain transpiration stream
- stem
- to identify them- plants are left in dyed water to stain the xylem
- 2. Sucrose is actively pumped into the phloem via
the compainon cell
- 3. Hydrogen ions are actively
pumped out of the companion cell. They diffuse back via co-transport protein,
carrying with it a sucrose molecule.
- 4. Water
potential in phloem is lowered so water moves into the phloem (sieve tube
element) from the xylem via osmosis
- 5. Hydrostatic pressure increases so sucrose solution is forced downwards- mass flow.
- 4. Water
potential in phloem is lowered so water moves into the phloem (sieve tube
element) from the xylem via osmosis
- 3. Hydrogen ions are actively
pumped out of the companion cell. They diffuse back via co-transport protein,
carrying with it a sucrose molecule.
Comments
No comments have yet been made