Chapter 35: Water and Sugar Transport in Plants
Which of the following indicates the symplastic route in this figure?
A
Which of the following scenarios is correct?
A cell is placed in a hypotonic solution; there is a net movement of water into the cell.
In this figure, which cells secrete the Casparian strip?
A: endodermis
Sugars need to move throughout plants. Which of the following transport mechanisms move sugars in plants?
All are correct
Which of the following have a water potential made up of solute potential and a pressure potential?
All of the above
Based on Ernst Münch's pressure-flow hypothesis, which conditions would increase the rate of translocation within the phloem?
An increase in sucrose production at the source
Which of the following routes involve the use of aquaporins?
B
In this figure, which of the following tissues produces the root hairs?
B: pericycle
CAM plants can photosynthesize and grow, even with their stomata closed during the day. How is this possible?
CAM plants store carbon dioxide (CO2).
Which of the following statements best describes channel proteins?
Channel proteins form pores that selectively admit certain ions and are responsible for facilitated diffusion.
What role does cohesion play in the process of water movement from roots to leaves?
Cohesion causes the column of water to act as a continuous chain.
The endodermis is a cylindrical layer of cells that forms a boundary between the cortex and the vascular tissue. Which of the following best describes the function of the endodermis?
Controlling ion uptake and preventing ion leakage from the vascular tissue
Which of the following statements regarding evaporation in plants is true?
Evaporation in plants can be beneficial.
Which of the following statements best describes the pressure-flow hypothesis?
Events at source tissues and sink tissues create a pressure potential gradient in phloem.
Which of the following best describes the movement of sugars through the phloem during the growing season?
From mature leaves to roots and seeds
When ions accumulate in the xylem of roots at night, enough water enters the xylem via osmosis to force water up and out of low-growing leaves. This phenomenon is knows as which of the following?
Guttation
What causes guttation?
Positive pressure in the root xylem and a decreased rate of transpiration at night
Loading sucrose into the phloem at a source sometimes requires the plant to expend energy. How is sucrose loaded into the phloem against its concentration gradient?
Protons are pumped out of the cell through proteins. They diffuse back into the cell through cotransporters, which allow sucrose through at the same time.
Which of the following is not accurate with regards to dry or salty soils?
Salty and dry soils tend to have few solutes and, thus, high water potentials.
To test the effects of soil moisture on spruce tree physiology, you measure the water potential of branches taken from two sets of identical trees: Set A is well watered, and set B is poorly watered. Which data set represents reasonable results from this experiment?
Set A: -0.7 MPa; set B: -2.1 MPa
What is the difference between simple diffusion, osmosis, and active transport?
Simple diffusion uses a concentration gradient and requires no adenosine triphosphate (ATP). Osmosis is a term used only for the movement of water. Active transport expends energy (needs ATP).
After leaving a tray of vegetables out for several hours, you find that the celery stalks are no longer crisp. How could you treat the celery stalks to correct the situation?
Soak them in cool water.
Water potential has two major components: solute potential and pressure potential. Which of the following statements is true regarding these two components?
Solute potential is the tendency of water to move by osmosis, whereas pressure potential is the tendency of water to move in response to pressure.
Loss of water via evaporation from the aerial parts of a plant is called transpiration. Transpiration occurs whenever which of the following sets of conditions are met?
Stomata are open; the air surrounding leaves is drier than the air inside leaves.
Which of the following statements is true of cotransporters?
Symporters transport solutes against concentration gradients using the energy released when a different solute moves in the same direction.
An animal cell and a plant cell are placed in a highly hypotonic solution. What will happen?
The animal cell will burst.
Scientists subjected a corn plant to different light intensities while measuring the xylem pressure in the leaves. They found that the brighter the light, the more negative the pressure in the xylem. Which of the following is the best interpretation of these results?
The increased light intensity increased the rate of transpiration, which increased the tension within the xylem.
What happens when the plant loses water faster than it is able to replace it?
The leaves wilt.
How can plants with low solute potential grow in dry soils?
The plant's solute potential and soil water potential are both low.
Water pressure (not accounting for gravity) follows the equation ψ = ψP + ψS. Which of the following statements best describes this equation?
The potential energy of water in a particular location is the sum of the pressure potential and the solute potential that it experiences.
Which of the following best describes the function of carrier proteins?
They are proteins that undergo conformational change and transport bound molecules.
Plants that live in dry environments have several structural features that allow them to conserve water. Which set of characteristics best describes plants that live in a dry environment?
Thick cuticle; sunken stomata surrounded by hairs
Sugars made at a source are translocated to nearby sinks that are often on the same side of the plant. Why does this happen?
Vascular tissue in the leaf and stem is organized into discrete bundles that run the length of the organ.
How does water movement differ over short distances compared with long distances?
Water can move a short distance in xylem via root pressure or capillary action; long-distance transport of water depends on movement along a steep water-potential gradient.
If a cell is in osmotic equilibrium with its surroundings, what would be the effect of increasing the solute concentration outside the cell?
Water would flow from the cell to the outside environment.
Water potential is the potential energy that water has in a particular environment compared with the potential energy of pure water at room temperature and atmospheric pressure. Under these conditions, pure water has a water potential of 0. Where would you find high and low water potential?
You would find high water potential in the roots of a plant and low water potential in the leaves of the plant.
Why is phloem unloading passive in young leaves but active in the roots of a sugar beet plant?
Young leaves immediately use unloaded sucrose, whereassucrose builds up in storage cells of sugar beet roots.
Active transport moves molecules __________ an electrochemical gradient and always involves __________.
against; membrane proteins
CAM and C4 photosynthetic cycles are adaptations in some plants. Which of the following is a benefit of their adaptation?
all of the above
All of the following are involved in the cotransport of protons and sucrose for phloem-loading of sieve-tube elements except ___________________.
an antiporter that transports protons and sucrose together into sink cells
In which of the following routes does water flow outside the plasma membranes?
apoplastic
Which of the following statements best describes the cortex?
consists of ground tissue and stores carbohydrates
Which cell layer filters water and solutes moving into or out of the vascular tissue of the roots?
endodermis
Water moves from plant roots to leaves in what type of transport?
passive
Transport of water through the xylem is __________.
passive, requiring no energy expenditure by the plant
Which part of the plant is this aphid likely feeding on?
phloem
Which structure is necessary for the symplastic pathway of water transport in a plant?
plasmodesmata
The cohesion-tension theory of water movement in the xylem states that water, as it evaporates through the stomata, pulls additional water from the xylem because of water's cohesive nature. The resulting tension in the xylem __________.
pulls more water up from the roots
Which of the following phloem cells lack nuclei and most organelles?
sieve-tube elements
How do salt-adapted species deal with low water potentials in soil?
they accumulate solutes in their root cells
____________ is the movement of sucrose and other products through the plant.
translocation
In the atmosphere, water exists as a __________ with a solute potential of __________ MPa.
vapor, 0
Expanding the volume of a cell pushes its membrane out. What prevents plant cells from bursting?
wall pressure
Transpiration is driven by __________.
water loss from aerial plant parts
