The Student Room Group
When water arrives at the endodermis, it encounters a barrier to the apoplast pathway (as you know) This is beasuse the cells of the endodermis have celss walls thickened with a waxy material called suberin, which is impermeable to water. The suberin forms a band around the cells which is called the casparian strip and the cells are also tightly packed together so water cant get between them. Thus the only pathway through the endodermis is through the cells themselves, the symplast pathway :smile:
Reply 2
ok thanks.......but what advantage is this to the cell that the water moves through the symplastic pathway as opposed to the apopolastic pathway?
i guess an advantage may be that cells are prevented from becoming flaccid (so they remain turgid at all time) which in turn can help with its metabolic reactions (because metabolic reactions take place in solution)....thats what i think
Reply 4
As far as I can recall, the endodermis is impregnated with suberin. This causes the water to take the symplast pathway instead of the apoplast. The effect of the casparian strip is to regulate the ion uptake by plants. How you ask? Well the cytopllasm of endodermal cells is selective about the type & number of ions wghich the plant absorbs. Only the ions absorbed by the the endodermis are available to be carried up to the xylem vessel. In this way, you can see, ion uptake regulation.

Hope that helps :smile:
Reply 5
Yup, basically it just gives the plant more control about what is taken up into the xylem.
Reply 6
oxymoron
Yup, basically it just gives the plant more control about what is taken up into the xylem.

Yes :smile:
Reply 7
yep, it alllows the plant to control the ion uptake.
Reply 8
Doesn't it also increase the pressure of water so as to increase root pressure at the base of the xylem to allow movement of water upwards ? (part of the many theories behind movement of water UP the xylem)
Reply 9
Ferry
Doesn't it also increase the pressure of water so as to increase root pressure at the base of the xylem to allow movement of water upwards ? (part of the many theories behind movement of water UP the xylem)

Huh?
Reply 10
Ferry
Doesn't it also increase the pressure of water so as to increase root pressure at the base of the xylem to allow movement of water upwards ? (part of the many theories behind movement of water UP the xylem)


It seems to be a logical, and correct theory.
Reply 11
WokSz
It seems to be a logical, and correct theory.

Hmm...how is it increasing the water pressure?
Reply 12
As the apoplast pathway is barred, the water can only enter the xylem through the symplast pathway. However, the water will only enter through passage cells in the endodermis. As there are a few passage cells, the water will build up and in a way 'queue' up. This increases the hydrostatic pressure.
Reply 13
WokSz
As the apoplast pathway is barred, the water can only enter the xylem through the symplast pathway. However, the water will only enter through passage cells in the endodermis. As there are a few passage cells, the water will build up and in a way 'queue' up. This increases the hydrostatic pressure.

Hmm OK thanks :biggrin:

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