Transport in plants Flashcards
Why do plants need transport systems?
To move substances to and from cells fast
What does phloem transport?
Sugars
What does xylem transport?
Water and mineral ions
What system do xylem and phloem make up in a plant?
Vascular system
What does the Xylem look like/ where is it on the cross section of a root?
A cross in the middle of the root
What do the phloem look like/ where are they on the cross section of a root?
4 Triangle shapes in between the cross shape of the xylem
Where is the xylem located on a leaf cross section?
The top
Where is the phloem located on a leaf cross section?
The bottom
Where is the xylem located on a stem cross section?
The middle
Where is the phloem located on a stem cross section?
The outside
Describe the key feature of xylem.
• Long tube-like elements
• The cells are dead (so no cytoplasm)
• Walls thickened with lignin
• Water moves into and out of the xylem the link small pits in the walls where there’s no lignin
Describe the key features of phloem.
• Transports sugars
• Arranged in tubes
• Contains sieve tube elements and companion cells
What are the key features of sieve tube elements (in phloem)
• Living cells
• Have holes in to allow solutes to pass through
• No nucleus and very few organelles
• Thin cytoplasm
What are companion cells? What do they do?
Because sieve tubes elements don’t have a nucleus, the companion cells carry out the living functions for both themselves and the sieve tubes (eg: provide energy for active transport of sugars)
Where does water enter the plant and how?
Through the root hair cells into the roots via osmosis
How/ why does the water travel down a water potential gradient in a plant?
Because water is constantly evaporated from the leaves and absorbed via the roots, this creates a gradient that keeps water moving though from the roots (high water potential) to the leaves (low water potential)
What is the symplast pathway?
Water travels through the living parts of the cells (the cytoplasm)
What are plasmodesmata?
Small microscopic channels that connect cell cytoplasms in plants
What is the apoplast pathway?
Water goes through non-living parts of the cells (cell walls).
What is the Casparian strip and what pathway is it involved in?
A waxy strip in cell walls that forces water travelling via the apoplast pathway into the symplast pathway
What is the main water pathway and why?
The apoplast pathway because it provides the least resistance
Where does water leave the plant from?
The stomata
How do cohesion and tension help move water up plants?
Water molecules are cohesive meaning they stick together and the evaporation of water creates tension (suction) which pulls the water up the leaf
What is adhesion in transpiration?
Water molecules being attracted to the walls of the xylem vessels
