LSU BIOL 1202 (Pomarico) - Ch. 36 Answers

Transpiration in plants requires _____. I) adhesion of water molecules to cellulose II) cohesion between water molecules III) evaporation of water molecules IV) active transport through xylem cells V) transport through tracheids

I, II, III, and V

Some botanists argue that the entire plant should be considered as a single unit rather than a composite of many individual cells. Which of the following cellular structures best supports this view?

plasmodesmata

Select the accurate statement about water potential.

Water in a turgid cell has positive pressure potential.

Which of the following is a correct statement about a difference between xylem and phloem transport?

Xylem sap moves up; phloem sap moves up or down.

Plants must always compromise between _____ and _____.

maximizing photosynthesis ... minimizing water loss

Water potential is generally most negative in which of the following parts of a plant?

mesophyll cells of the leaf

A plant cell with a ψs of -0.65 MPa maintains a constant volume when bathed in a solution that has a ψs of -0.30 MPa and is in an open container. The cell has a

ψp of +0.35 MPa.

A student is performing a chemical analysis of xylem sap. This student should not expect to find much _____.

sugar

The solute most abundant in phloem sap is _____.

sugar

Transpiration provides the driving force for the movement of water from the soil to the highest leaves of plants. Transpiration is also linked to other processes in plants, including photosynthesis and the transport of mineral nutrients. Which of the following statements correctly describe(s) a relationship between transpiration and other processes in plants? Select all that apply.

- Transpiration is important in cooling leaves on warm, sunny days. - In most plants, the highest rate of transpiration occurs when the rate of photosynthesis is also highest. - Open stomata provide a low-resistance pathway for CO2 to enter and for water to exit the leaf. - To minimize water loss during dry conditions, most plants must also restrict their ability to carry out photosynthesis.

If ΨP = 0.3 MPa and ΨS = -0.45 MPa, the resulting Ψ is ________.

-0.15 MPa

Hydrogen bonding is crucial to the transpiration-cohesion-tension mechanism. Drag the labels to their appropriate locations in the table to show how hydrogen bonding is involved at different points in the ascent of xylem sap.

1. one ball above the other pic 2. balls side by side with water line showing 3. balls side by side with no water line showing 4. ball with H and O present

Chemical bonds hold together the atoms that make up a molecule. Molecules may also be attached to one another by chemical bonds. The figure shows how hydrogen bonds attach water molecules to other water molecules. Drag the terms on the left to the appropriate blanks on the right to complete the sentences. 1. A water molecule consists of one oxygen atom joined to each of two hydrogen atoms by a(n) __________, a type of bond in which the electrons do not spend equal time with the two atoms involved. 2. Because oxygen is more electronegative than hydrogen, the electrons in a water molecule spend more time closer to ___________. 3. The unequal distribution of electrons means that each of the three atoms in a water molecule has a __________. This makes water a polar molecule. 4. The oxygen of a water molecule has a partial ________ charge. 5. Each hydrogen in a water molecule has a partial __________ charge. 6. A weak bond called a(n) ___________ forms as a result of the attraction between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of a nearby water molecule.

1. polar covalent bond 2. oxygen 3. partial charge 4. negative 5. positive 6. hydrogen bond

The process that plants use to transport water and minerals from their roots to their shoots -- known as the transpiration-cohesion-tension mechanism -- relies at many points on the hydrogen bonds formed by water molecules. Before looking more carefully at the role of hydrogen bonding in the ascent of xylem sap, let's review the transpiration-cohesion-tension mechanism, as shown in the figure. Drag the labels to their appropriate locations on the flowchart to show the sequence of events that pulls xylem sap from the roots to the shoots of a plant. Note that the steps in the flowchart correspond to the numbered locations in the image above.

1. water vapor moves from leaf air spaces to the atmosphere through stomata 2. water evaporates from the cell walls of the leaf mesophyll cells, increasing the surface tension of water in the leaves 3. water molecules pull on adjacent water molecules all the way down the xylem, they also adhere to the walls of xylem cells 4. water enters the xylem after it is absorbed by the plants roots

Arrange the following five events in an order that explains the mass flow of materials in the phloem. 1. Water diffuses into the sieve tubes. 2. Leaf cells produce sugar by photosynthesis. 3. Solutes are actively transported into sieve tubes. 4. Sugar is transported from cell to cell in the leaf. 5. Sugar moves down the stem.

2, 4, 3, 1, 5

A plant leaf is constructed from a variety of cell types with specialized structures and functions. Many of the properties of leaf cells facilitate some aspect of water transport. The diagram below shows a cross section through a leaf. Drag the labels to the appropriate targets to match the function with the structure indicated in the diagram. Labels may be used once, more than once, or not at all.

A. cells that transport water from the roots to the leaves B. a group of different cell types involved in long-distance transport of water and nutrients C. cells with a coating that prevents evaporation of water D. cells with a coating that prevents evaporation of water E. cells where most evaporation of water in the leaf occurs F. cells that control the rate of water loss from the leaf

The apoplast and symplast are two regions of the plant that serve as pathways for water and solute transport over both short and long distances. These pathways are represented by the arrows in the diagram below, which shows three adjacent cells in a leaf or root. Sort each statement into the appropriate bin.

Apoplastic Pathway: - is depicted by the red arrow in the diagram - involves water transport outside the protoplast - consists of a porous matrix of hydrophilic monomers Symplastic Pathway: - is depicted by the blue arrow in the diagram - involves water moving via plasmodesmata - can involve water entering vacuoles Neither Pathway: - requires water to cross multiple plasma membranes

Several tomato plants are growing in a small garden plot. If soil water potential were to drop significantly on a hot, summer afternoon, which of the following would most likely occur?

Size of stomatal openings would decrease.

If isolated plant cells with a water potential averaging -0.5 MPa are placed into a solution with a water potential of -0.3 MPa, which of the following would be the most likely outcome?

The pressure potential of the cells would increase.

A plant cell is placed in distilled water, as shown in the figure. There is a net uptake of water by osmosis, causing the cell to become turgid. Select the correct statement about this setup, after the cell is fully turgid.

The water potentials (Ψ) of the cell and its surroundings are the same.

Ignoring all other factors, what kind of day would result in the fastest delivery of water and minerals to the leaves of an oak tree?

a very hot, dry, windy day

Water follows a specific path as it moves from the xylem in the vein of a leaf to the air outside the leaf. Drag the labels into the flowchart to show the sequence of events after water enters a leaf in the xylem. Not all labels will be used.

a) water exits the xylem and enters the walls of surrounding cells b) water spreads as a film in and on the surface of mesophyll cell walls c) water evaporates from the surface of mesophyll cells d) water vapors diffuses through the air spaces of the leaf e) water vapor exits the leaf through the stomata

In addition to transporting sugar, the phloem also _____.

all of the above

The value for Ψ in root tissue was found to be -0.15 MPa. If you take the root tissue and place it in a 0.1 M solution of sucrose (Ψ = -0.23 MPa), the net water flow would ________.

be from the tissue into the sucrose solution

A water molecule could move all the way through a plant from soil to root to leaf to air and pass through a living cell only once. This living cell would be a part of which structure?

the endodermis