Transport in Plants Flashcards
Know about transport in Plants
What are ways in which a root hair cell is adapted for its function?
root hairs have large surface area which means allows them to absorb water through the process of osmosis
Fully permeable cell wall that allows water and minerals to
pass through freely.
A partially permeable membrane that allows water but not
most solutes to pass through
Cytoplasm and cell sap have a lower water potential (more
solutes than water) than external environment so water
enters passively down a concentration gradient
List properties of xylem vessels
Xylem vessels are made up of several vessel elements
arranged end to end.
Vessel elements are elongated and narrow
Vessel elements were originally normal plant cells in whose
walls lignin was laid down.
Lignin is impermeable to water, and as more is laid down in
the wall of a cell, the cell eventually dies.
What are tracheids
These are also dead cells with lignified walls.
Their ends are not open and so do not form vessels.
The ends taper off.
They have pits and so they can help in the transport of
water.
They are the main conducting tissue in gymnosperms
(primitive)
What are Fibres
These cells are also elongated and dead.
Their function is to support the plant.
Explain movement of water from root hair to xylem
Water moves across the cortex into the xylem because
the water potential in the xylem vessels is lower than
that of the cortical cells.
The water takes two possible routes across the cortex:
Apoplast pathway
Symplast pathway
Briefly describe the symplast pathway
The water moves into the
cytoplasm or vacuole of the
cortical cells.
It then passes into adjacent cells
through the plasmodesmata.
List factors that increase the rate of transpiration
Several things can increase the rate of transpiration.
These include:
Low humidity
Rise in temperature
Increased wind speed
Opening of the stomata
Light intensity
How does transpiration occur?
Mesophyll cells are not tightly packed and have air
spaces among them.
Water from the mesophyll cells evaporates into the air
spaces making the air spaces saturated with water
vapour.
There is direct contact between the air inside the leaf
and the air outside the leaf through the stomata.
Explain steps 1 to 3 in translocation
What are parenchyma cells?
These are like regular plant cells.
They have unthickened cell walls and the organelles
that would be found in a plant cell.
However, because they are not exposed to light, they
have no chloroplasts.
They have a variety of shapes but are usually
isodiametric (same size in all directions).
