Experimental Plant Science Test 3

Transpiration

Movement of water and mineral nutrients from soil to atmosphere in plants.

Evapotranspiration

Landscape-level movement of water from soil to atmosphere.

What controls transpiration?

Turgid guard cells.

Why are stomates generally open during the day?

They are open for photosynthesis and closed at night to conserve water.

What type of photosynthesis do xerophytes use?

CAM photosynthesis.

How does H2O move in and out of guard cells?

Potassium enters, water enters, opening the cell; potassium is released, cell closes with less water.

Leaf adaptations to arid environments

Thick cuticle, long dermis, hairs, sunken stomates.

What are cortical cells composed of?

Cellulose; they absorb water.

Explain the transpiration-cohesion theory.

Water has cohesive and adhesive properties due to its polarity.

What makes up water's free energy?

Solute and pressure potential.

What is the sign of solute potential?

0 or (-).

What happens when solute concentration increases?

Decreases solute potential/makes it more negative.

What is the sign of pressure potential?

Positive (Turgor pressure).

What are the major essential nutrients?

Nitrogen, Phosphorus, Potassium, Magnesium, Sulfur.

What does Nitrogen do?

Forms proteins, nucleic acids, and chlorophyll.

What does Phosphorus (P) do?

Forms nucleotides, nucleic acids, and phospholipids.

What does Potassium (K) do?

Regulates guard cells.

What does Magnesium (Mg) do?

Essential for chlorophyll.

What does Sulfur (S) do?

Part of certain amino acids.

What does Calcium (Ca) do?

Component of plant cell walls.

Why is this production of hydroponic tomatoes important?

Better pest control and less heavy and expensive.

What is phytoremediation used for?

Using plants to clean up contaminated soils, sediments, and water.

Where does the translocation of sugars occur?

In living phloem sieve tube members.

Is ATP required for translocation of sugars?

Yes.

What does the translocation of sugars do?

Moves sucrose and other organic compounds from a source to a sink.

What is the pressure flow hypothesis?

Explains the translocation of sugars from source to sink.

How does water and mineral nutrient transport differ from sugar transport?

Water/mineral transport relies on solute and pressure potential without ATP via xylem; sugar transport requires ATP and phloem.

What two plants provide commercial sucrose worldwide?

Sugar cane and sugar beet.

What is the range of light wavelengths plants use?

400-700 nm.

Which pigments are primary?

Chlorophyll a P680/P700.

List accessory pigments.

Rest of chl a, Chl b, Carotenoids (Carotenes and Xanthophylls).

Where are pigments and protein complexes formed?

In the thylakoid membrane.

What portion of chlorophyll is hydrophobic and hydrophilic?

Tail is hydrophobic; body is hydrophilic.

Are carotenoids hydrophobic or hydrophilic?

Mainly hydrophobic.

Why do chlorophyll pigments break down in fall?

Due to lower levels of nitrogen.

What is the limiting growth nutrient in plants?

Nitrogen.

Why don’t carotenoids break down during the fall?

Because CO2 is easy for the plant to obtain.

What are two phases of photosynthesis and their locations?

Light reactions in thylakoid membrane; Calvin Cycle in stroma.

What happens during carboxylase?

CO2 enters the plant.

What happens during oxygenase?

O2 fits into the active site.

What enzyme is responsible for carbon fixation in the C3 cycle?

Rubisco.

Explain photorespiration and is it good for the plant?

Rubisco combines O2 with RuBP; it's inefficient since O2 replaces CO2.

Where is Rubisco 4mM found?

In the stroma.

Why is Rubisco 4mM unique?

Abundant enzyme slower than most substrates; ensures carbon fixation occurs.

What is the most abundant protein on earth? What percentage does it make up in leaves?

Carbon; 25% of the leaf.

How many times faster does Rubisco fix CO2 than O2?

80 times.

What is the ratio that CO2 outruns oxygenation?

3:1.

In what environments do plants utilize the C4 Cycle?

In tropical grasses and warm-season prairie grasses.

Why do some plants have the C4 cycle over the C3 cycle?

Due to warmer climates.

Explain what happens during the C4 cycle.

Increases CO2 concentration in bundle sheath cells; rescues photorespiration and water loss in hot, dry environments, costs ATP.

What environment do plants use the CAM cycle?

In arid environments.

When are stomates open in CAM cycle plants?

At night.

What is the initial carboxylating enzyme of the CAM cycle?

PEP carboxylase.