Xylem and phloem

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  • Created by: Isobel
  • Created on: 17-02-14 09:33
Why do plants need a transport system?
Because many cells in a plant are far away from the supply and thus would not recieve enough nutrients or water to survive. For example, roots can obtain water easily but cannot absorb sugars from the soil.
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Describe the structure of xylem and phloem in a young root
Vascular bundle is found at centre. There is a large central core of xylem (often in shape of x) and phloem is found between arms of the xylem. This arrangment provides strength to withstand the pulling forces to which the root is exposed.
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Describe the structure in a young root (surrounding the vascular bundle)
Around the vascular bundle is the endodermis which has a key role in getting water into xylem tissues. Inside the endodermis is a layer of meristem tissues (cells that remain able to divide)
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Where are the vascular bundles found in a stem?
Near the outer edges of the stem
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Where are the xylem, phloem and cambiumfound in a stem?
Xylem is found near the inside of vascular bundle and phloem is found near outside. The cambium is found in between the xylem and phloem.
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How do the vascular bundles in stems of woody and non- woody plants differ?
In non- woody plants, the bundles are seperate and discrete. Whereas, in woody plants, the bundles are seperate in young stems but continuous in older stems
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Where in a leaf are the vascular bundles found?
They form the midrib and veins of the leaf
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True or false: in a leaf, the xylem can be seen on top of the phloem?
True
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Name 3 of the roles that Lignin have in a xylem vessel?
1.It waterproofs the walls of the cells which leaves the cells to die and their end walls and content to decay. 2.It strengthens the vessel wall and prevents it from collapsing. 3.It forms patterns in cell walls which prevents vessel from being rigid
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What adaptions allow xylem tissues to do their job?
It is made from dead cells end- to- end to form a continuous tube so able to carry water, the tubes are narrow so water column does not break easily and pits in the lignified walls allow water to move sideways from one vessel to another.
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Why is the flow of water not impeded?
Because there us no cell contents or end walls. Also lignin thickenign prevents walls from collapsing
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Structure of sieve tubes (found in phloem)
It has very little cytoplasm and no nucleus. They line up end-to end to form a tube in which plant transports sugars.
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Structure of companion cells (found in phloem)
Have a large nucleus and a dense cytoplasm. They also have numerous mitochondria to prdocue ATP. Its job is to carry out the metabolic processes needed by sieve tube element.
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How are companion cells and sieve tubes connected?
Their cytoplasm is linked through many plasmodesmata
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Name some comparisions between xylema and phloem
Xylem: dead, Phloem: living. X: one way flow, P: can flow either way. X: no contents, P:few contents. X: no end walls, P: end walls adapted as sieve plates.
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Card 2

Front

Describe the structure of xylem and phloem in a young root

Back

Vascular bundle is found at centre. There is a large central core of xylem (often in shape of x) and phloem is found between arms of the xylem. This arrangment provides strength to withstand the pulling forces to which the root is exposed.

Card 3

Front

Describe the structure in a young root (surrounding the vascular bundle)

Back

Preview of the front of card 3

Card 4

Front

Where are the vascular bundles found in a stem?

Back

Preview of the front of card 4

Card 5

Front

Where are the xylem, phloem and cambiumfound in a stem?

Back

Preview of the front of card 5
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