Chapter 36: Practice Test Flashcards

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Which of these is not transported via the symplasm?



The ancestors of land plants were aquatic algae. Which of the following is not an evolutionary adaptation to life on land?

C3 photosynthesis


Which of the following is a correct statement about sugar movement in phloem?

Movement can occur both upward and downward in the plant


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

warm, dry day


Arrange the following five events in an order that explains 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


Assume that a particular chemical interferes with the establishment and maintenance of proton gradients across the membranes of plant cells. All of the following process would be directly affected by this chemical except

xylem transport


In plant roots, the Casparian strip is correctly described by which of the following?

it ensures that all the water and dissolved substances must pass through a cell membrane before entering the stele


What is the main cause of guttation in plants?

root pressure


Most angiosperms have alternate phyllotaxy. What allows each leaf to get the maximum exposure to light and reduces shading of lower leaves?

leaf emergence as an angle of 137.5 from the site of previous leaves


Plants do not have a circulatory system like that of some animals. If a given water molecule did circulate (go from one point in a plant to another and back), it would require the activity of

both the xylem and phloem


Phloem transport is described as being from the source to the sink. Which of the following would most accurately complete this statement about phloem transport as applied to most plants in the late spring?

Phloem transports ___ from the ___ source to the ___ sink.

sugars; leaf; apical meristem


Which structure or compartment is not part of the apoplast?

the lumen of a sieve tube


Pine seedling grown in sterile potting soil grow much slower than seedlings grown in soil from the area where the seeds were collected. This is most likely because

the normal symbiotic fungi are not present in the sterilized soil and water and mineral uptake is faster when mycorrhizae are present


Which one of the following statements about transport of nutrients in phloem is false?

companion cells control the rate and direction of movement in phloem sap


All of the following has an effect on water potential in plants except

DNA structure


If the guard cells and surrounding epidermal cells in a plant are deficient in potassium ions, all of the following would occur except

leaf temperatures would decrease


Which of the following statements about transport in plants in false?

Gymnosperms can sometimes develop especially high root pressure, which may account for the rise of water in tall pine trees without transpiration pull


Photosynthesis begins to decline when leaves wilt because

stomata close, preventing CO2 entry into the leaf


Active transport of various materials in plants at the cellular level requires all of the following except

xylem membranes


movement of phloem sap from source to sink

may translocated sugars from the breakdown of stored starch in a root up to developing shoots


What would enhance water uptake by a plant cell?

positive pressure on the surrounding solution


Which of the following has the lowest (most negative) water potential_

leaf air spaces


Transpiration in plants requires all of the following except

active transport through xylem cells


Which of the following statements is false concerning the xylem?

movement of materials is by mass flow; materials move owing to a turgor pressure gradient from "source" to "sink"


Active transport involves all of the following except the

diffusion of solute through the lipid bilayer of a membrane


Active transport would be least important in the normal functioning of which of the following plant tissue types?

stem xylem


All of the following are adaptations that help reduce water loss from a plant except



Water flows into the source end of sieve tube because

sucrose has been actively transported into the sieve tube, making it hypertonic


The water lost during transpiration is an unfortunate side effect of the plant's exchange of gases. However, the plant derives some benefit from this water loss in the form of

evaporative cooling and mineral transport


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 cannot be used to support this view?



Long-distance electrical signaling in the phloem has been shown to elicit a change in all of the following except

a switch from C4 to C3 photosynthesis


Stomata open when guard cells

open because of a decrease in turgor pressure


Root hairs are most important to a plant because they

increase the surface area for absorption


What is the role of proton pumps in root hair cells?

acquire minerals from the soil


All of the following normally enter the plant through the roots except

carbon dioxide


What regulates the flow of water through the xylem?

the evaporation of water from the leaves


If you were to prune the shoot tips of a plant, what would be the effect on the plant and leaf area index?

bushier plants - higher leaf area indexes


A fellow student brought in a leaf to be examined. The leaf was dark green, thin, had a stoma on the lower surface only, and had a surface area of 100 square meters. Where is the most likely environment where this leaf was growing?

a tropical rain forest


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 part of which structure?

the endodermis


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

mesophyll cells of the leaf


Guard cells do which of the following?

help balance the photosynthesis-transpiration compromise


Xylem vessels, found in angiosperms, have a much greater internal diameter than tracheids, the only xylem conducting cells found in gymnosperms. The tallest living trees, redwoods, are gymnosperms. Which of the following is an advantage of tracheids over vessels for long-distance transport to great heights?

cohesive forces are greater in narrow tubes than in wide tubes of the same height, and adhesive forces are proportionally greater in narrower cylinders than in wider cylinders


The amount and direction of movement of water in plants can always be predicted by measuring which of the following?

water potential


Which of the following experimental producers would most likely reduce transpiration while allowing for normal growth of a plant?

increasing the level of carbon dioxide around the plant


Which of the following is not an important component of the long-distance transport process in plants?

the root parenchyma


Which of the following best explains why CAM plants are not tall?

they wold be unable to move water and minerals to the top of the plant during the day


Phloem transport of sucrose can be described as going from "source to sink." Which of the following would not normally function as a sink?

mature leaf


As a biologist, it is your job to look for plants that have evolved structures with a selective advantage in dry, hot conditions. Which of the following adaptations would be least likely to meet your objective?

plants that do not produce abscisic avid and have a short, thick taproot


A plant developed a mineral deficiency after being treated with fungicide. What is the most probable cause of the deficiency?

mycorrhizal fungi were killed


Which of the following is responsible for the cohesion of water molecules?

hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule


All of the following involves active transport across membranes except

the movement of sugar from one sieve-tube member to the next


Which of the following is an adaptation that enhances the uptake of water and minerals by roots?

active uptake


What is the driving force for the movement of materials in the phloem of plants?

a difference in osmotic water potential between the source and the sink


Which of the following would be least likely to affect osmosis in plants?

receptor proteins in the membrane


Which of the following does not affect self-shading?

stem thickness


Which of the following is not a function of the plasma membrane proton pump?

equalizes the charge on each side of a membrane


What is the main force by which most of the water within xylem vessels moves toward the top of a tree?

evaporation of water through stoma


In which plant cell or tissue would the pressure component of water potential most often be negative?

stem xylem


The following factors may sometimes play a role in the movement of sap through xylem. Which one depends on the direct expenditure of ATP by the plant?

concentration of ions in the symplast


The opening of stomata is thought to involve

an increase in osmotic concentration of the guard cells


Compared to a cell with a few aquaporins in its membrane, a cell containing many aquaporins will

have a faster rate of osmosis


Which of the following statements is false about bulk flow?

it depends on the force of gravity on the column of water


Which of the following would likely not contribute to the surface area available for water absorption from the soil by a plant root system?



One is most likely to see guttation in small plants when the

root pressure exceeds transpiration pull


Which structure or compartment is not part of the plant's apoplast?

the lumen of a sieve tube


According to the pressure flow hypothesis of phloem transport

solute moves from a high concentration in the "source" to a lower concentration in the "sink"


Which of the following statements about xylem is incorrect?

it transports mainly sugars and amino acids


Water rises in plants primarily by the cohesion-tension model. Which of the following is not true about this model?

the "tension" of this model represents the excitability of the xylem cells


Which of the following is not part of the transpiration-cohesion-tension mechanism for the ascent of xylem sap?

active pumping of water into the xylem of roots