Transport in plants Flashcards
Why do plants need a specialised transport system?
- to move products of photosynthesis, water, and oxygen around from their place of origin
- most plants are large and so have to transport substances huge distances from root to tip
- SA: vol is small in plants (even though for leaves SA:vol high)
Define vascular system
a system of transport vessels in plants or animals
Define herbaceous
having a fleshy/soft stem
Define vascular bundle
The vascular system of herbaceous dicots, made up of xylem and phloem tissue
Define dicotyledonous
plants that produce two seed leaves
How do you tell if a plant is mono- or di- cotyledonous from its leaves?
- Monocots have vessels parallel to the leave
- Dicots have vessels which branch out from a central vessel
What is the vascular bundle made up of?
Xylem and phloem tissue
What are the products of photosynthesis?
Carbohydrates, proteins, lipids, nucleic acids
What are the products of photosynthesis known as collectively?
Organic compounds
Why do plants need water? (5 reasons)
- to maintain turgidity of cells
- to transport nutrients around the plant
- to create an aqueous environment for reactions to occur
- to cool plants by evaporation
- for photosynthesis
How is water transported in the plant?
Via the xylem
From the inside to the outside what tissues are present in a dicot root section?
xylem phloem pericycle endodermis cortex epidermis- root hair cells
In which part of the root is water taken up?
Root hairs
Which part of the root do the lateral roots grow from?
The pericycle
Why does the root have so many root hairs?
Increases the surface area able to take up water
How does water enter the root?
By osmosis
What must the water potential of the soil be relative to the root in order for water to be taken up?
The water potential of the soil must be less negative than the water potential of the root
How does the plant ensure the water potential of the root is more negative than the soil?
-ions from the soil are ACTIVELY pumped into the root
What does active pumping mean?
-Energy is required for the movement to occur
What pathway is taken by the water to go from the soil to the xylem?
root hair cell cortex endodermis pericycle xylem
What are the 2 different routes the water can take?
Apoplast
Symplast
What is the function of the pericycle?
-it is meristematic and produces the lateral roots
What is the function of the endodermis?
-contains a ring of suberin which is impermeable to water
What is the function of the cortex?
-stores a large amount of starch
What shape is the xylem tissue?
-star-shaped
What is the apoplast pathway?
Water travels through the cellulose cell wall
What is the symplast pathway?
Water travels through the cytoplasm and from cell to cell via plasmodesmata
What is the advantage of travelling through the cellulose cell wall?
It offers the path of least resistance
What is the Casparian strip made of?
Suberin
What is the key property of the Casparian strip?
It is impermeable to water
What happens to water travelling via the apoplast pathway when it reaches the Casparian strip?
It cannot continue and so is diverted to the symplast pathway
What is the advantage of water being diverted into the symplast pathway?
It allows the plant to control the movement of water into the root via osmosis
How does water enter the xylem from the endoderm?
- endodermal cells acitively pump salts into the xylem
- this makes the water potential of the xylem more negative than the endodermal cells
- this means water enters the xylem via osmosis
- ensures a large water potential gradient is maintained
Where is the Casparian strip located?
In the endodermal cells
How do endodermal cells move ions into the xylem?
Active transport
Once water has entered the xylem how does it move?
As a continuous stream
What force is created by the bonds between water molecules?
Cohesion