Plant

Why is stomatal control important?

It helps plants respond to environmental variability.

Why does CAM have high WUE?

Its stomata open at night.

What type of light promotes stomatal opening?

Blue light.

What structural feature controls guard-cell shape?

The arrangement of cellulose microfibrils.

What relative humidity does a porometer assume inside the leaf?

100% relative humidity.

What provides the energy for secondary active transport?

The favorable concentration gradient of another ion.

What must be known to estimate stomatal conductance?

Water vapor concentration in the leaf mesophyll.

What leaf feature affects fluid transport resistance?

Leaf vein density.

What is the difference between primary and secondary active transport?

Primary uses ATP directly; secondary uses an ion gradient.

What is secondary active transport?

One ion's favorable gradient drives another ion against its gradient.

What is primary active transport?

ATP directly pumps ions against their concentration gradient.

What is passive transport?

Movement that requires no added energy.

What does WUE stand for?

Water-use efficiency.

What does a porometer estimate?

Stomatal conductance.

What contributes to liquid-water transport resistance in leaves?

Resistance within the leaf transport pathway.

Water moves from what potential to what potential?

High → low water potential.

Rank CAM, C4, and C3 plants by WUE.

CAM > C4 > C3

Passive transport moves substances in what direction?

Down their concentration gradient.

How is WUE expressed?

CO₂ gained ÷ H₂O lost.

How is internal leaf water vapor estimated?

From leaf temperature.

How does water entry help stomata open?

 It increases guard-cell turgor.

How does stomatal control affect WUE?

 It can increase water-use efficiency.

How does leaf hydration status affect stomatal opening?

It helps regulate whether stomata open or close.

How does increased vein density affect pathway resistance?

It lowers pathway resistance.

How does increased CO₂ affect stomatal aperture?

 It decreases stomatal opening.

How does decreased CO₂ affect stomata?

It promotes stomatal opening.

Does primary active transport require ATP?

Yes. ATP directly supplies the energy.

Does higher or lower WUE indicate better efficiency?

Higher WUE.

Besides CO₂, water, and light, what regulates stomata?

Signaling molecules.

About what % of water loss occurs through the cuticle?

About 5%.

About what % of plant water loss occurs through stomata?

About 95%.

 Why does C4 generally have higher WUE than C3?

C4 stomata do not need to open as widely.

What transporter uses ATP during stomatal opening?

H⁺-ATPase.

What does the H⁺-ATPase do?

Uses ATP to pump H⁺ against its concentration gradient.

What causes voltage-gated K⁺ channels to open?

A specific change in membrane voltage.

What receptor detects blue light in guard cells?

Phototropin

What does phototropin activation trigger?

A signaling cascade that activates H⁺-ATPase.

What happens to the guard-cell membrane after H⁺-ATPase activation?

The membrane becomes hyperpolarized.

What opens because the guard-cell membrane becomes hyperpolarized?

Voltage-gated K⁺ channels.

What does the H⁺/Cl⁻ symporter do during stomatal opening?

Brings Cl⁻ into the guard cell.

Why does water enter the guard cell?

The osmotic potential becomes favorable for H₂O to enter through aquaporins.

What happens after water enters and turgor pressure increases?

The guard cells change shape, causing the stomatal pore to open

What is the first step of stomatal opening?

Blue light hits the phototropin receptor on the guard-cell membrane.

What happens after blue light activates phototropin?

A signaling cascade activates the H⁺-ATPase.

What does activation of the H⁺-ATPase cause?

H⁺ is pumped out, causing membrane hyperpolarization.

What happens because of membrane hyperpolarization?

Voltage-gated K⁺ channels open.

What happens to Cl⁻ during stomatal opening?

Cl⁻ is brought into the guard cell through an H⁺/Cl⁻ symporter.

What happens to water after ions accumulate in the guard cell?

Water enters through aquaporins because of the favorable osmotic potential.

What ultimately causes the stomatal pore to open?

Increased water causes increased turgor pressure, changing guard-cell shape and opening the pore.

What is the equation for the potential energy of solute species j?
What does R represent?
What does T represent?
What does Cj represent?
What does z represent?
What does F represent?
What does Ψ represent?
What does Vj represent?
What does P represent?

uj= RT ln(Cj)+zFΨ+V+jP

Gas constant.
Temperature
Concentration of species j.
Electric charge of the ion.
Faraday constant.
Electrical potential of the solution.
Volume associated with species j.
Turgor pressure.