OCR AS Biology (F211) - Jan 2013.

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Metal ions and nutrients actively pumped into roots, this lowers water potential.

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Water then diffuses down its water potential gradient passively into the roots of the plant.

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The water molecules will now either travel by the apoplast, symplast or vacuolar pathways through various parts of the root cells until they reach the casparian strip which forces all water travelling via the apoplast pathway into the cell (a waterproofing layer if you will).

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Because the water molecules are now in the cells prior to the xylem they will have to pass through its plasma membrane, hence the level of water entering the xylem is now controlled.

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Water moves up the xylem of plants from higher areas of hydrostatic pressure to lower areas of hydrostatic pressure under tension through "mass flow".

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Water mocules are adhesive and cohesive, which means they become attracted to the walls of the xylem and to other water molecules. Hence, very soon "columns of water" form within the xylem vessels.

•

Metal ions and nutrients actively pumped into roots, this lowers water potential.

•

Water then diffuses down its water potential gradient passively into the roots of the plant.

•

The water molecules will now either travel by the apoplast, symplast or vacuolar pathways through various parts of the root cells until they reach the casparian strip which forces all water travelling via the apoplast pathway into the cell (a waterproofing layer if you will).

•

Because the water molecules are now in the cells prior to the xylem they will have to pass through its plasma membrane, hence the level of water entering the xylem is now controlled.

•

Water moves up the xylem of plants from higher areas of hydrostatic pressure to lower areas of hydrostatic pressure under tension through "mass flow".

•

Water mocules are adhesive and cohesive, which means they become attracted to the walls of the xylem and to other water molecules. Hence, very soon "columns of water" form within the xylem vessels.