Xerophytes & Transpiration Factors

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xerophytes

A plant adapted to live in dry conditions

They have a range of adaptations to reduce the loss of water vapour by transpiration.

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xerophytes

Leaves Small to reduce the surface area Thick to reduce surface area: volumes ratio

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xerophytes

Sunken Stomata

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xerophytes

Stomata

Set deep inside the leaf so that they are at the base of a depression full of water vapour

Some plants open their stomata at night to store and absorb CO2

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xerophyte

Thick waxy cuticles

reduce water loss through the epidermis

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Xerophytes

Rolling up of leaves

Lower surface faces inside and traps humid air next to the stomata

Varies with conditions

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Xerophytes

Leaf hairs

Trap damp air

Reduces air movement

Cut down transpiration

Factors Affecting Transpiration

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Measures the water absorption

Estimate the rate of transpiration

Air/water tight

Water transpiredWater entering to

xylem

Potometer

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Light intensity:

Factors affecting rate of transpiration

Affects the opening and closing of the stomata

ROT Indirect effect

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Humidity:

Factors affecting rate of transpiration

Humid atmosphereContains a lot of H2O

moleculesReduction of the water

potential gradient between the air spaces and atmosphere

ROT decreasesLow humidity increases

ROT

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Temperature:

Factors affecting rate of transpiration

Temperature kinetic energyRate of diffusion

through the stomata pores

Air is able to hold more water molecules at higher temperatures

ROT

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Wind speed:

Factors affecting rate of transpiration

Still air makes the H2O molecules to accumulate around the stomata pores (leaves)

Reduces the H2O potential gradient and slows the ROT

Wind disperse H2O molecules

gradient in H2O potential ROT