coconut64
Badges: 16
Rep:
?
#1
Report Thread starter 4 years ago
#1
Explain how endodermis cell carries out its function in the uptake of water and minerals inthe plant.

Selective uptake / Active uptake / transport of minerals (byendodermis cells);Into symplast pathway;Active transport of minerals into pericycle;Water follows by osmosis;Water and minerals move into xylem vessels;

These are the points that need to be included to score marks but I don't understand how to structure it as I don't know the order of the sequence. I thought ions are actively transported to the cytoplasm but the mark scheme says pericycle.. Can anyone clarify? Thanks.
0
reply
RMNDK
Badges: 3
Rep:
?
#2
Report 4 years ago
#2
(Original post by coconut64)
Explain how endodermis cell carries out its function in the uptake of water and minerals inthe plant.

Selective uptake / Active uptake / transport of minerals (byendodermis cells);Into symplast pathway;Active transport of minerals into pericycle;Water follows by osmosis;Water and minerals move into xylem vessels;

These are the points that need to be included to score marks but I don't understand how to structure it as I don't know the order of the sequence. I thought ions are actively transported to the cytoplasm but the mark scheme says pericycle.. Can anyone clarify? Thanks.
At the Casparian Strip, ions are actively transported into the cytoplasm because, as it says, the membrane selective uptakes which ions and minerals it wants for any biochemical processes. Meanwhile the water moves by osmosis and joins the symplastic pathway.

(Many sources say different things) I learnt that the ions are also actively transported into the pericycle, which are then actively transported into the xylem because on of their functions is to act as a source cell: something that'll lower the water potential (it's a source of solutes) so that water can move from the source to it's target/sink.
By actively transporting the ions from the pericycle into the xylem, you're lowering the water potential so water can move by osmosis into the xylem.

Other sources argue that because of the transpiration pull, the water potential at the bottom of the xylem should be very low. Also, the movement of sugars and ions via phloem differs to that in the xylem (quite complicated but in essence it can move both up and down). This means it can (and is usually) concentrated at the bottom of the xylem. So water would just simply move by osmosis into the xylem with no need for this extra active transport of ions into the pericycle.

I would just go with the mark scheme since that's what your exam board wants. Movement of water and nutrients in plants isn't completely understood anyway.
I guess the best way to structure it would be:
The endodermis cells actively transport minerals across the cell membrane and into the cytoplasm joining with the symplastic pathway. They then actively transport the minerals into the pericycle which causes the water potential of the pericycle to be more negative than the water potential of the endodermis. This causes water to move into the pericycle. There is a lower water potential in the xylem so water moves by osmosis into the xylem.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Have you experienced financial difficulties as a student due to Covid-19?

Yes, I have really struggled financially (22)
14.01%
I have experienced some financial difficulties (42)
26.75%
I haven't experienced any financial difficulties and things have stayed the same (65)
41.4%
I have had better financial opportunities as a result of the pandemic (23)
14.65%
I've had another experience (let us know in the thread!) (5)
3.18%

Watched Threads

View All