Transport in plants Flashcards
Name 3 plant tissues and their functions
Cuticle- Provides a waterproof layer of wax on the outside of a leaf, made of cutin
Epidermis- A single layer of cells that secretes cutin
Parenchyma- Packing calls that store food and provide support
What is the role of the phloem?
Transports sugars such as sucrose around the plant (up and down) and other assimilates
What is the role of the xylem?
Transports water and minerals up the plant, minerals will be ions such as phosphate
What is the role of cambium?
A dividing cell that can provide more xylem and phloem (stem cell), located between the xylem and phloem in the vascular bundle
How do single celled organisms respire?
Due to the large SA:V they get oxygen through diffusion from the air
Why do some small plants not need transport systems?
They are small enough to absorb minerals directly from the environment and so they don’t have roots. E.g Moss
What is a vascular plant?
A plant that has a specialised transport system used to transport water, minerals and sugars.
Has a low SA:V and contains a phloem and xylem
Where are the vascular bundles located one the stem?
Found around the sides of the stem with a pith in the middle
What do the vascular bundles form?
They form the midrib and veins of the leaf to transport water, sugar and minerals around the plant
Define pressure potential
The pressure that is exerted on a cell wall
What is the result of increased pressure?
Reduced intake of water
How does water enter the xylem across the root?
Via osmosis
How does water enter the root in terms of water potential?
Mineral ions are actively transported into the root hair cell,
This lowers the water potential of the cytoplasm,
Water enters root hair cell by osmosis,
How does water cross the cortex and enter the xylem?
Water moves across the cortex via osmosis,
Minerals are actively transported into the xylem,
This leaves the water potential in the xylem and water follows by osmosis
Define the three pathways of water movement and what route they take
Apoplast- Around the cell wall
Symplast- Through the cytoplasm
Vacuolar- Through the vacuoles
What is the casparian strip made of?
Made of a waxy substance called Suberin
Explain the apoplast pathway
Water molecules go around the call wall,
It does not pass through any plasma membranes,
Can transport dissolved minerals and salts,
Takes water to the casparian strip where it enters the endodermis’s cytoplasm and continues in the symplast route
Explain the symplast pathway
Water enters through the plasma membrane into the cytoplasm,
Passes through the plasmodesmata to enter other cells
Explain the vacuolar pathway
Water molecules travel through the cytoplasm and vacuoles
What is the role of the casparian strip?
Prevents ions from the xylem leaking back into the cortex,
Forces water molecules from the apoplast pathway into the cytoplasm
Define transpiration
The process of water movement through a plants from the roots and its evaporation from aerial parts such as the leaves
What are the three ways the xylem facilitates movement?
Root pressure,
Transpiration pull,
Capillary action
Explain how root pressure creates movement in the xylem
Minerals move into the xylem via active transport which causes water to move in via osmosis,
This increases hydrostatic pressure which pushes water up the xylem,
This will only get water up the start of stem
Explain how transpiration pull facilitates movement
As water molecules evaporate from leaves other water molecules are pulled up as they stick together,(cohesion)
The pull from above causes tension but lignin prevents collapse.
This is known as cohesion-tension theory
Explain how capillary action facilitates movement
Water molecules are attracted to the sides of the xylem which is made of lignin,(adhesion)
Due to the xylem being so narrow the forces of attraction pull up the water via the sides of the xylem
