Water Transport in Plants - Biology II

Select all true statements about transpiration. - It requires energy input from the plant. - It results from ion transport into xylem vessels. - It is driven by evaporation. - It creates tension in the xylem.

- It is driven by evaporation. - It creates tension in the xylem.

Select all true statements about transpiration. - It depends on cells with functional cell membranes. - It is the most important force that helps move water across long distances in plants. - It transports starch to roots for seasonal storage. - It pulls water upward from roots to leaves.

- It is the most important force that helps move water across long distances in plants. - It pulls water upward from roots to leaves.

Select all functions of stomata. - Protect from insect damage. - Minimize water loss. - Prevent UV damage. - Admit carbon dioxide.

- Minimize water loss. - Admit carbon dioxide.

Choose all that contribute to the surface area through which a plant can absorb water. - Trichomes. - Mycorrhizae. - Root hairs. - Stomata.

- Mycorrhizae. - Root hairs.

Choose all components of the water potential of a solution in a plant cell. - Solute concentration. - Pressure. - Osmosis. - Gravity. - Aquaporins.

- Solute concentration. - Pressure. - Gravity.

Select all cell types that typically carry minerals via bulk transport upwards in a plant. - Vessel elements. - Tracheids. - Companion cells. - Sieve tube members.

- Vessel elements. - Tracheids.

What is a turgid cell?

A cell that's content/vacuole pushes against the cell wall, therefore appears plump and slightly rounded.

Most plants can sustain full transpiration as long as the relative humidity in the atmosphere is A. 95% or less. B. Not 100%. C. 98% or less.

A. 95% or less.

Transpiration rates may be slowed down due to the closing of stomata when A. Atmospheric CO2 concentrations are high. B. Atmospheric temperatures are 20-30oC. C. Red light is detected by a plant. D. Blue light is detected by a plant.

A. Atmospheric CO2 concentrations are high.

The addition of solutes to water A. Decreases the water potential. B. Does not change water potential. C. Increases the water potential.

A. Decreases the water potential.

Water will move A. From a location with a higher water potential to a location with a lower water potential. B. From a location with lower solute concentration to a location with higher solute concentration regardless of the water potential. C. From a location with higher solute concentration to a location with lower solute concentration regardless of the water potential D. From a location with a lower water potential to a location with a higher water potential.

A. From a location with a higher water potential to a location with a lower water potential.

Which of the following statements accurately describes the role of blue light in stomatal opening? A. It triggers proton transport, which generates a proton gradient used to transport K+ into the cell. B. It activates light sensitive K+ channels, which transport K+ into the cell. C. It stimulates the opening of aquaporins, which allows K+ to be transported into the cell together with water.

A. It triggers proton transport, which generates a proton gradient used to transport K+ into the cell.

Root pressure is highest when transpiration rate is A. Low. B. High.

A. Low.

When minerals are relocated via bulk flow in the xylem, they A. Must move with the upward flow of water in the xylem. B. Always move opposite to the water flow in the xylem. C. Can move upwards (with water in xylem) or downwards (opposite to the water flow) depending on when they are needed.

A. Must move with the upward flow of water in the xylem.

A turgid cell is A. Stiff. B. Limp.

A. Stiff.

Which of the following statement accurately describes the relationship between CO2 concentration and stomatal opening? A. Stomata may close when CO2 concentrations are high. B. Stomata may close when CO2 concentrations are high, but only during the night. C. Stomata may close when CO2 concentrations are low. D. Stomatal closing is not influenced by the concentration of CO2.

A. Stomata may close when CO2 concentrations are high.

In most terrestrial plants, water enters through the roots and exits the plant through the ______. A. Stomata. B. Lenticels. C. Epidermis. D. Cuticle.

A. Stomata.

A substance moving from cell to cell through plasmodesmata is following the A. Symplast route. B. Transmembrane route. C. Apoplast route.

A. Symplast route.

Unlike C3 plants, CAM plants A. Take up CO2 at night. B. Close stomata at warm temperatures. C. Respond only to blue light. D. Produce stomata only on lower leaf surfaces.

A. Take up CO2 at night.

Difference in turgor pressure drive the transport of carbohydrates through A. The phloem. B. Both the xylem and the phloem. C. The xylem.

A. The phloem.

If the water potential outside a cell is -0.3 MPa and the water potential inside the cell is -0.5 MPa, will water move and in what direction? A. Water will move into the cell. B. Water could move into or out of the cell depending on temperature and salt concentration. C. Water will move out of the cell.

A. Water will move into the cell.

The plant hormone that regulates stomatal opening in response to drought is ______ ______.

Abscisic acid (fill-in-the-blanks).

A substance that moves through the space between cells is following the ______ route.

Apoplastic (fill-in-the-blanks).

The bulk flow of water across membranes is faster than predicted by osmosis alone because water can move through specialized channels called ______.

Aquaporins (fill-in-the-blanks).

In a tree in the middle of summer, phloem will move mainly in which direction?

From leaves to roots.

Plasmolysis would occur when A. A cell is placed in an isotonic solution. B. A cell is placed in a very concentrated solution. C. A cell is placed in a very diluted solution. D. A cell is turgid.

B. A cell is placed in a very concentrated solution.

The movement of water across membranes is aided by transport channels called _______. A. Proton pumps. B. Aquaporins. C. Plasmodesmata. D. Vessel elements.

B. Aquaporins.

What type of light induces stomata to open as sunlight increases the need for evaporative cooling? A. Ultra-violet. B. Blue. C. Green. D. Red.

B. Blue.

When a gas-filled bubble blocks a xylem element, dehydration and plant death can occur as a result of which of the following? A. Transport. B. Cavitation. C. Equilibrium. D. Cohesion.

B. Cavitation.

Turgor pressure requires A. Cell walls to allow for expansion (sometimes almost doubling) of cells as they take up water. B. Cell walls to constrain the expansion of cells as they take up water. C. Cell membranes to constrain the expansion of cells as they take up water.

B. Cell walls to constrain the expansion of cells as they take up water.

The pressure-flow hypothesis describes which of the following? A. Xylem transport. B. Phloem transport. C. The flooding response. D. Drought resistance.

B. Phloem transport.

In early spring, as the buds of a tree are just beginning to open, the main source and sink of sugars in the phloem are which of the following? A. Source: buds; Sink: roots. B. Source: roots; Sink: buds.

B. Source: roots; Sink: buds.

Which of the following is an example of translocation? A. Auxin is synthesized in an apical bud and diffuses to cells in the stem. B. Starch in a tuber is converted to sucrose and transported to a leaf bud. C. Minerals are absorbed in the root and transported to a leaf.

B. Starch in a tuber is converted to sucrose and transported to a leaf bud.

Evaporation of water in a leaf creates negative pressure in the xylem. This causes A. Water to slowly diffuse up the stem from the roots. B. Water to be pulled up the stem from the roots. C. Water to to be pushed from the stem down to the roots.

B. Water to be pulled up the stem from the roots.

The transpiration rate of a plant increases A. When air humidity increases. B. When air humidity decreases. C. When there is sunlight, regardless of air humidity.

B. When air humidity decreases.

In the pressure-flow hypothesis of movement of carbohydrates through the phloem, the mesophyll of leaves is thought to act as A. A flow regulator. B. A sink. C. A source.

C. A source.

What plant hormone mediates stomatal closure during daytime water stress? A. Gibberellin. B. Auxin. C. Abscisic acid. D. Ethylene.

C. Abscisic acid.

Typically air bubbles that form in xylem vessels A. Can pass through pits to adjacent vessels only when the plant is actively transpiring. B. Can pass through pits to adjacent vessels. C. Can not pass through pits to adjacent vessels.

C. Can not pass through pits to adjacent vessels.

Phloem transport is driven by differences in ______ pressure.

Turgor (fill-in-the-blanks).

A water column with a smaller diameter will have a A. The same tensile strength as a water column with a larger diameter. B. Lower tensile strength than a water column with a larger diameter. C. Higher tensile strength than a water column with a larger diameter.

C. Higher tensile strength than a water column with a larger diameter.

The high tensile strength of water is important for A. Developing root pressure when the atmospheric humidity is high. B. Pushing water through sieve elements via translocation. C. Pulling water up the transpiration stream.

C. Pulling water up the transpiration stream.

Under mild drought conditions, plants may be stunted because A. Embolisms prevent water from moving through the xylem. B. Increased transpiration results in the loss of sugars. C. Stomata are closed so carbon dioxide is not taken in for photosynthesis. D. Under water stress, plants cannot take up minerals.

C. Stomata are closed so carbon dioxide is not taken in for photosynthesis.

Which of the following accurately describes how sucrose moves in the phloem? A. Sucrose can only move up a plant (roots to leaves). B. Sucrose can only move down the plant (leaves to roots). C. Sucrose can move both up and down a plant.

C. Sucrose can move both up and down a plant.

Root pressure is present even when transpiration is low, due to A. The movement of water from the phloem to the xylem. B. An increase in bulk water flow out of the root hairs. C. The continued accumulation of ions in the roots. D. A decrease in microbial activity during these times.

C. The continued accumulation of ions in the roots.

What root structure acts as a molecular filter, controlling the passage of solutes that have entered through the symplast? A. The pericycle. B. The epidermis. C. The endodermis. D. The cortex.

C. The endodermis.

Can root pressure be present when the transpiration rate is low and why? A. No, because ions can only enter the root during the day when plants are actively photosynthesizing and stomata are therefore open. B. Yes, because root pressure is caused by capillary forces in the xylem. C. Yes, because root pressure is caused by accumulation of ions in the root which can occur at all times.

C. Yes, because root pressure is caused by accumulation of ions in the root which can occur at all times.

The solute potential of pure water is A. Minus one. B. Plus one. C. Zero. D. Variable, depending on pressure potential.

C. Zero.

______ ______ in root endodermal cells contain suberin to limit the movement of minerals and water.

Casparian strips (fill-in-the-blanks).

The current explanation for the movement of water through the xylem is called the ______-______ theory.

Cohesion-tension (fill-in-the-blanks).

Cavitation in the xylem water column results from which of the following? A. Excess mineral uptake. B. Root pressure. C. Dehydration. D. Air bubbles.

D. Air bubbles.

Which of the following is key for active transport to occur? A. The direction of movement is one-way. B. No membrane channel is involved. C. Protons are moving out of the cell. D. Energy input is required.

D. Energy input is required.

Under what conditions would you expect to see the highest transpiration rates? A. High temperature and high humidity. B. Low temperature and low humidity. C. Low temperature and high humidity. D. High temperature and low humidity.

D. High temperature and low humidity.

The high tensile strength of water results from the cohesiveness of water molecules for each other and adhesiveness to the wall of cells in the xylem. These are both due to the the effects of A. Carbon chains. B. Calcium binding. C. Polymerization. D. Hydrogen bonding.

D. Hydrogen bonding.

An important function of pits in vessel walls is to A. Allow sugars to move between vessels. B. Provide structural support to the long vessels. C. Provide a barrier to pathogen movement. D. Prevent air bubbles from passing to adjacent vessels.

D. Prevent air bubbles from passing to adjacent vessels.

What feature of guard cells allows them to open stomata when turgor pressure in them changes? A. They don't have cell walls on the inside. B. They have Casparian strips in their cell walls C. Their cell walls are thinner on the inside and thicker elsewhere. D. Their cells are thicker on the inside and thinner elsewhere.

D. Their cells are thicker on the inside and thinner elsewhere.

The active uptake of ions into root cells results in which of the following? A. They are stimulated to produce thicker cell walls. B. They burst and are sloughed off. C. Their turgor pressure decreases. D. Their turgor pressure increases.

D. Their turgor pressure increases.

The cells that border stomata are called ______ cells.

Guard (fill-in-the-blanks).

True or False: Sucrose can be transported in the phloem both up and down the plant.

True; Sucrose can be transported in the phloem both up and down the plant.

The water potential of a solution has two components: ______ ______ (such as pressure, or gravity), and the concentration of ______ in the solution.

Physical forces; solute (fill-in-the-blanks).

If a cell loses water, the cell membrane pulls away from the wall in a process called ______.

Plasmolysis (fill-in-the-blanks).

The accumulation of ions in roots results in the creation of root ______.

Pressure (fill-in-the-blanks).

The model for phloem transport is called the ______-______ hypothesis.

Pressure-flow (fill-in-the-blanks).

In a typical terrestrial plant, water is absorbed mostly in the zone of the root that has ______ ______.

Root hairs (fill-in-the-blanks).

Carbohydrates in the phloem move from source to ______.

Sink (fill-in-the-blanks).

Crassulacean acid metabolism (CAM) plants conserve water in dry environments by opening ______ at night.

Stomata (fill-in-the-blanks).

Structural features on leaf epidermal cells, called ______, have evolved to minimize water loss, while allowing carbon dioxide uptake.

Stomata (fill-in-the-blanks).

The ______ strength of a column of water varies inversely with the diameter of the column.

Tensile (fill-in-the-blanks).

Water molecules form hydrogen bonds with one another so they are difficult to pull apart; consequently water is said to have a high ______ ______.

Tensile strength (fill-in-the-blanks).

Water solutions that pass through the membranes of root endodermal cells will enter which structure?

The xylem.

Sugars manufactured in leaves are distributed to other plants parts through the phloem by a process know as ______.

Translocation (fill-in-the-blanks).

Water is pulled through the xylem by the process of ______.

Transpiration (fill-in-the-blanks).

A cell that is swollen with water is said to be ______.

Turgid (fill-in-the-blanks).

The hydrostatic pressure that builds as water enters plant cells and presses on the cell wall, is called ______ pressure.

Turgor (fill-in-the-blanks).

Plants are always dealing with the trade-off between open stomata, in which CO2 is taken in but ______ is lost, and closed stomata, in which the same compound is retained, but CO2 is not taken in.

Water (fill-in-the-blanks).

When stomata are open and the atmospheric humidity is low, ______ ______ exits the plant.

Water vapor (fill-in-the-blanks).

Transpiration aids in the movement of ______ and dissolved ______ over long distances in plants.

Water; minerals (fill-in-the-blanks).