Chapter 36 Quiz

Breeders are working to develop plants that grow better in salty environments. Choose the characteristics that they should attempt to breed into plants.

-Ability to exclude salt -Ability to dilute salt as it enters the plant -Ability to secrete salt that has entered the plant

-The movement of water into and out of plant cells described by water potential which is the ability of water to do work. -Water potential is the sum of pressure potential , which is the pressure of water against the cell wall, and solute potential, which is the effect of solutes on water. -Pressure raises water potential but solutes lower it.

-Because water will always try to move from areas of higher water potential to areas of lower water potential one can predict the direction of water movement. -For example, if a cell is placed in a solution with lower water potential, water will move out of the cell. -If a cell placed in a solution with higher water potential, water will move into the cell.

Through genetic engineering, you are developing a plant that will have increased tolerance to drought. Choose the traits from the list below that would be desirable in this plant.

-Dormancy during a dry season -Production of stomatal crypts -Increased production of trichomes

Place the terms in the correct locations to complete these sentences about plants and flooding.

-Flooding is detrimental to plant growth because it causes low levels of oxygen in soil. -Because of this, roots have difficulty transporting minerals and carbohydrates. -Root growth can also be altered because of changes in hormone levels. -For example, ethylene production increases which acts to suppress root elongation. -Gibberellin and cytokinin production decreases which suppresses growth of new roots.

Where would the turgor pressure be the lowest?

In the roots and meristem

How do Osmosis and diffusion differ?

Osmosis occurs when water molecules cross a membrane from an area of high water concentration to an area of lower concentration, while diffusion is the movement of any small non-polar molecule across a membrane from high to low concentration.

Classify the items according to whether they are transported in the xylem, phloem, or both.

Phloem- sucrose, organic acids, mRNA, and proteins Xylem- water, mineral from soil both- hormones

Water potential (ΨW) is calculated using the following equation: ΨW = ΨP + ΨS. Where ΨP is the pressure potential and ΨS is the solute potential. What would occur if ΨP decreases in one phloem cell in comparison to the ΨP in a neighboring phloem cell?

Water would flow into the phloem cell with the lower ΨW until ΨW was the same in both cells.

Opening of stomata involves a tradeoff between the conflicting needs to

open to maximize CO2 uptake for photosynthesis but close to minimize water loss through transpiration.

If a plant had no Casparian strips

potentially toxic ions would enter the vascular tissue.

A plant cell placed in a hypertonic medium will

shrink

All of the following describe functions of root hairs except which?

store sugars

Translocation involves

the transport of carbohydrates in phloem

A 5% urea solution is hypotonic to a 10% urea solution.

true

In plants the ____________ conducts water and dissolved minerals, while the ____________ conducts sucrose to different areas in a plant.

xylem; phloem

Place the terms in the correct locations in the sentences to describe movement of materials in the phloem.

-In the pressure-flow hypothesis, carbohydrates flow from source to sink. -At the site of photosynthesis, a process called phloem-loading pumps sucrose into sieve tubes. -Sugars then travel from mesophyll cells to companion cells where it will be transferred to sieve cells. -Transport can be through the symplast but much occurs through the apoplast. -Once sieve tubes are loaded with sugars, their lower water potential draws water from neighboring xylem cells. -The resulting increased turgor pressure moves materials through the phloem. -At the sink, active transport of solutes out of the cells also lowers pressure to further drive mass flow in the phloem.

Choose the items responsible for the high tensile strength of water in xylem.

-hydrogen bonds -cohesion among water molecules -adhesion between water molecules and xylem cell walls -small diameter of tracheids and vessel elements

Transpiration happens because

-water has polar covalent bonds. -water has nonpolar covalent bonds.

Place the events in the correct sequence to describe the process of root pressure.

1. Ion concentrations increase in root xylem at night. 2. water is drawn into roots via osmosis 3. water moves up the plant and through leaves. 4. water exits via cells along the edge of the leaves via guttation.

Place the events in the correct sequence to explain the function of guard cells in opening stomata.

1. Stoma is closed 2. K+ and Cl- pumped into the guard cells 3. Water potential of the guard cell decreases 4. Water flows into the guard cells 5. Vacuoles filled with water 6. Turgor pressure of the guard cell increases 7. Guard cell bulge and blow outwards 8. Stoma opens

Place the events in the correct order to describe cavitation.

1.vessel is broken or damaged 2. air bubble enters cell 3. cohesion interrupted 4. cavitation occurs

A plant is subjected to a toxin that blocks potassium channels in the membranes of guard cells and prevents the passage of K+ out of the cell. This would lead to a reduction in the intake of carbon dioxide into the plant.

False

Water potential (ΨW) is calculated using the following equation: ΨW = ΨP + ΨS. Where ΨP is the pressure potential and ΨS is the solute potential. What would occur if the ΨP is 0.6 MPa for both cells but the first cell had a ΨS of -0.53 and the second cell had a ΨS of -0.76?

The first cell would have a higher ΨW and water would flow out of the cell into the second cell.

Water potential (ΨW) is calculated using the following equation: ΨW = ΨP + ΨS. Where ΨP is the pressure potential and ΨS is the solute potential. At the point in the video when urea is shown on one side of the membrane, which side of the membrane has the lowest water potential prior to any osmotic activity?

The side with the urea has the lowest water potential.

Water potential (ΨW) is calculated using the following equation: ΨW = ΨP + ΨS. Where ΨP is the pressure potential and ΨS is the solute potential. At the point in the video when urea is shown on one side of the membrane, which side of the membrane has the greatest water potential prior to any osmotic activity?

The side without the urea has the greatest water potential.

Phloem loading is the process of

carbohydrates entering the sieve tubes at the source.

transpiration is driven by

evaporation caused by the lower water vapor pressure outside the leaf relative to inside the leaf.