Ch.37 Transport in Plants
Long-distance water transport is mainly driven by the ________ of water from leaf surfaces.
evaporation
What is the major stress imposed by flooding?
The loss of available oxygen in the soil
If a cell has a solute potential of -0.5 MPa and a pressure potential of 0.2 MPa, then it will be in equilibrium with a solution that has a water potential of which of the following?
-0.3 MPa
Order the steps that lead to early morning guttation, beginning with the first step.
1) Root xylem accumulates high concentrations of ions. 2) Water follows the ions into the interior of the root. 3) Water is pushed upward in the xylem. 4) Droplets of water are observed on leaves.
Select all plant responses to flooding.
Abnormal growth Hormone levels charge
What plant hormone mediates stomatal closure during daytime water stress?
Abscisic acid
Cavitation in the xylem water column results from which of the following?
Air bubbles
The movement of water across membranes is aided by transport channels called which of the following?
Aquaporins
What types of plants typically form aerenchyma?
Aquatic plants
Select all environmental conditions in which water stress in common.
Arid environments Freezing temperatures Windy environments
Select all true statements about transpiration.
It is driven by evaporation It creates tension in the xylem
How are simplastically transported minerals able to bypass the endodermal barrier that limits apoplastic transport?
By moving through the endodermal cytosol
What gas enters plants through the stomata and is used for photosynthesis?
CO2
The selective uptake of minerals into roots is possible due to the pressure of
Casparian strips
When a gas-filled bubble blocks a xylem element, dehydration and plant death can occur as a result of when of the following?
Cavitation
What directly drives phloem transport between cells of sugar source and sink?
Differences in turgor pressure
Water always moves in which direction?
From an area of higher water potential to an area of lower water potential
The function of succulent leaves in mangroves is to do which of the following?
Dilute salt
Select all physical forces that influence long-distances water transport in the xylem.
Evaporation of water at plant surfaces Cohesion of water molecules to each other Tension that pulls water through the cells Adhesion of water to the walls of conducting cells
Select all factors that lower the water potential of the soil.
Excess fertilizer Drought conditions
True or false: In the phloem, organic molecules are only transported from the roots to the shoots.
False Transport occurs both up and down the plant through the phloem.
Name the kidney-shaped structures that border stomata.
Guard cells
Select all plant adaptations to drought, including those that limit water loss.
Hard, thick leaves Dormancy Loss of leaves
Under what conditions would you expect to see the highest transpiration rates?
High temperature and low humidity
If the water potential outside a cell is -0.3 MPa and the water potential inside the cell is -0.5 MPa, water will move how?
Into the cell
Select all true statements about osmosis.
It carries molecules along a concentration gradient It requires a membrane
Select all statements that accurately describe functions of evaporation for plants.
It helps to cool above-ground portions of the plant It helps to distribute water throughout the plant body It aids in the movement of dissolved minerals for long distances
Select all true statements about transpiration.
It is the primary way in which water is transported long distances in plants. It moves water upward from roots to leaves.
Sucrose is an important compound in plants for which reason?
It is the transport form of carbohydrates.
Select all true statements about blue light.
It promotes K+ transport against a concentration gradient It triggers proton transport, driving the opening of K+ channels
While walking through a field that has been flooded with rain water for several weeks, you notice that plant leaves are dying out. Why would the leaves dry out when water is abundant?
Lack of oxygen in the roots
Select all ways in which plants have evolved to prevent excessive water loss by transpiration.
Leaf drop Regulation of stomata opening
In response to drought, abscisic acid allows potassium ions to do which of the following?
Leave guard cells, causing them to close
Select all functions of stomata.
Minimize water loss Admit carbon dioxide
What happens when solute concentrations increase inside guard cells?
Osmotic water uptake occurs via plasma membrane aquaporins
Match each type of diffusion with description.
Passive diffusion -- The transport of molecules across a membrane without the aid of transport proteins. Facilitated diffusion -- The transport of molecules across a membrane with the aid of transport proteins.
Difference in turgor pressure drive the transport of carbohydrates through structure?
Phloem
This vascular tissue transports organic molecules, such as sucrose, in both directions (from roots to leaves and from leaves to roots).
Phloem
The pressure-flow hypothesis describes which of the following?
Phloem transport
Select all places where aquaporins are found.
Plasma membrane Vacuolar membrane
Select all information needed to predict water movement using the water potential equation.
Pressure at the cell wall-membrane interface Solute concentration inside the plant cell Solute concentration outside the plant call
In early spring, as the buds of a tree are just beginning to open, the main source and sink are which of the following?
Roots and buds, respectively
The carbohydrate-rich fluid that moves throughout the plant is which of the following?
Sap
Select all ways in which plants can manage salt balance in a high salinity environment.
Secretion Exclusion Dilution
Name the structure that allows a plant to take up carbon dioxide for photosynthesis.
Stoma
Plant sap is rich in which of the following?
Sucrose
Which environmental factor affects the turgor pressure of guard cells?
Sunlight
The function of pneumatophores in mangroves is to do which of the following?
Take up oxygen
Why do many plants have vessels, when tracheids are narrower and consequently have higher tensile strength?
The benefits of high mass flow are important in vessels
The plasma membranes of cells in the endodermis contain many different proton pumps involved in the transport of minerals. What do these proton pumps do?
They transport specific ions into the stele against their concentration gradient.
How are minerals typically transported across the endodermis, in order to increase their concentration in the stele?
Through active transport
Select all cell types that carry minerals through a plant.
Tracheids Vessel elements
This type of evaporation drives water movement through the xylem.
Transpiration
What provides the main force for moving water from roots to leaves in the xylem?
Transpiration
True or False: Root pressure is present even when the transpiration rate is low.
True
What vascular tissue carries water molecules and dissolved minerals?
Xylem
The plant hormone that regulates stomatal opening in response to drought is _______ acid.
abscisic
Minerals move through the endodermis to the stele via
active transport
Aquatic plants produce specialized parenchyma with large air spaces, called ______ to allow oxidative respiration to occur.
aerenchyma
Transpiration rate increases with
an increase in guard cell turgor pressure
In contrast to the symplast, the _______ is composed of cell walls and intercellular spaces.
apoplast
A substance that moves through the space between cells is following the _________ route.
apoplastic
The bulk flow of water across membranes is permitted by water channels called ________.
aquaporins
Turgor pressure requires
cell walls to constrain the expansion of cells as they take up water
If you measure atmospheric humidity and transpiration rate in a tree, you will find that as humidity increases, transpiration rate
decreases
In roots, water and nutrient flow are controlled by Casparian strips embedded in cells of the _______.
endodermis
The cells that border stomata are called _______ cells.
guard
Plants that can tolerate saline soils are called _____.
halophytes
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 effects of
hydrogen bonding
Guard cells open when their solute concentrations
increase
Select all functions of the edt1 gene in Arabidopsis
increase root length enhance ABA levels
A long-term effect of flooding may be
leaf death due to root damage
Saline soil causes water stress in plants because it has a ______ water potential.
low
When guard cells are turgid, the stomatal pore opens between them, allowing air exchange with the spongy _______.
mesophyll
Flooding damages plants because _______ deprivation leads to decreased cellular respiration.
oxygen
Carbohydrates enter sieve tubes during the process of ______ loading?
phloem
Carbohydrates in storage organs are converted into sucrose and transported through the
phloem
Carbohydrates manufactured in leaves are distributed throughout the plant through the
phloem
The accumulation of sucrose in sieve tube members occurs as a result of
phloem loading
If a cell loses water, the cell membrane pulls away from the wall in a process called ______.
plasmolysis
In the water potential formula, turgor pressure is referred to as _______ potential.
pressure
The accumulation of ions in roots results in the creation of root ______.
pressure
The model for phloem transport is called the _________-_________ hypothesis.
pressure-flow
An important function of pits in vessel walls is to
prevent air bubbles from passing to adjacent vessels
The high tensile strength of water is important for
pulling water up the transpiration stream
Mechanisms to manage _____ stress include exclusion, dilution, and concentration.
salt
Carbohydrates in the phloem move from source to ______.
sink
The total water potential of a cell is obtained by adding the pressure potential and _____ potential.
solute
Carbon dioxide enters leaves through openings between guard cells, called ______.
stomata
Crassulacean acid metabolism (CAM) plants conserve water in dry environments by opening _____ at night.
stomata
Structural features on leaf epidermal cells, called ______, have evolved to minimize water loss, while allowing carbon dioxide uptake.
stomata
Under mild drought conditions, plants may be stunted because
stomata are closed so carbon dioxide is not taken in for photosynthesis
A substance moving from cell to cell through plasmodesmata is following the
symplast route
Select all forms of tissue-level transport.
symplastic apoplastic transmembrane
Unlike C3 plants, CAM plants
take up CO2 at night
The ______ strength of a column of water varies inversely with the diameter of the column.
tensile
The current explanation for the movement of water through the xylem is called the cohesion-_______ theory.
tension
If radioactive carbon dioxide is applied to a plant in a sunny dry atmosphere and another plant in a sunny humid atmosphere, and photographic film is placed over the plants,
the plant in the humid atmosphere will produce a darker image because it contains more radioactive carbon
Select all ways in which plants may encounter water stress in natural environments.
too little water too much salt too much water
Tissue-level transport occurs in three forms: ________, _______, and _______ transport.
transmembrane symplastic apoplastic
The movement of sugars from the cytoplasm into a vacuole is an example of
transmembrane transport
Evaporation of water from leaves, referred to as _______, benefits plants because it cools their surfaces and enables the movement of water from the soil to leaves.
transpiration
The main force for moving water from roots to leaves is called ______.
transpiration
A cell that is swollen with water is said to be _______.
turgid
Stomata open when the _______ pressure in guard cells increases.
turgor
The hydrostatic pressure that builds as water enters plant cells is a form of osmotic pressure called ______ pressure.
turgor
Plant strategies to limit _____ loss include dense trichomes, thick leaves, and placing stomata in pits.
water
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
The Greek letter psi is an abbreviation for _____ potential, which predicts the direction of water movement in a plant.
water
The _____ potential of saline soils is low, so it causes water stress in plants.
water
When stomata are open and the atmospheric humidity is low, _____ vapor exits the plant.
water
Evaporation aids in the movement of ____ and dissolved _____ over long distances in plants.
water minerals
What type of gradient enables transport from roots to shoots in the xylem?
water potential
Evaporation of water in a leaf creates negative pressure in the xylem. This causes
water to be pulled up the stem from the roots
Water and dissolved minerals are carried through the vascular tissue called ______.
xylem
Water solutions that pass through the membranes of root endodermal cells will enter which structure?
xylem
The solute potential of pure water is _____.
zero