When Plant Cells Lose Water

Plant Physiology

UNI

2009

Fully turgid cell

• In equilibrium with pure water

• Solutes in cell “pull” water in

• Pressure positive• Membrane pushed up

against wall• Wall stretched slightly

(most cells)• Leaf feels really stiff

WP = 0

PP = +15

SP = -15

Slight water loss (few %)

• Slight water loss• Almost no change in

water volume • Pressure changes

significantly (still +)• Solute potential does not

change significantly • Membrane still pushed up

against wall• Wall still stretched slightly

(most cells)• Leaf feels quite stiff

WP = -10

PP = +5

SP = -15

More water loss (few more %)

• Slight further water loss• Almost no change in

water volume • Pressure changes

significantly (still +)• Solute potential does not

change significantly • Membrane still pushed up

against wall• Leaf not very stiff

WP = -14

PP = +1

SP = -15

More water loss (wilting)

• Slight further water loss• Almost no change in

water volume • Pressure now just at zero • Solute potential still about

the same• Membrane just touching

wall • Leaf wilted

WP = -15

PP = 0

SP = -15

Even more water loss(cell plasmolyzing)

• Slight further water loss• More membrane pulling away

from wall (not attached)• Pressure still zero

(= atmosphere) • Significant change in water

volume • Solute becomes more

concentrated• Solute potential lower• Leaf still wilted, but alive

WP = -20

PP = 0

SP = -20

Yet more water loss(further plasmolysis)

• Slight further water loss• More membrane pulling away

from wall (not attached)• Pressure still zero

(= atmosphere) • Significant change in water

volume • Solute becomes more

concentrated• Solute potential lower• Leaf still wilted, but alive

WP = -25

PP = 0

SP = -25

Lethal water loss

• More further water loss• More membrane pulling

away from wall (not attached)

• Pressure still zero (= atmosphere)

• Solute becomes more concentrated, solute potential lower

• Irreversible loss of membrane & protein function

WP = -40

PP = 0

SP = -40

The End

• Plants can lose turgor (pressure) and not be harmed

• Cells can plasmolyze a bit and not be harmed

• If cells become sufficiently dehydrated, metabolic functions are reduced

• If they be come too dehydrated, they die