the answer is this:
definition: the ability of a cell to draw water into itself is called its water potential.
example: pure water has a water potential pf zero. As solutes are added to the water potential fall-it becomes negative.So a concentrated solution has a lower water potential(more negative) than pure water.
when two areas of different potentials are separated by a semi permeable membrane water moves form the less negative area to the more negative area.
This happens when red blood cells are placed in salt solution,water moves out of the cell in salt solution> the cell gets smaller and wrinkled appearance.the movement of water is down the water potential gradient.A water potential gradient is a measure of the difference in water potential between two areas.the greater the difference the steeper the gradient and the faster the movement of molecules along it.
this is little big answer but i hope u'll get it.
(+rep for sure
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