Download Ch 35 Plant Structure, Growth and Development

Ch 35 Plant Structure, Growth and Development
Question
Answer
You are studying a plant from the arid southwestern United States.
Development of large leaf surfaces to
Which of the following adaptations is least likely to have evolved in
absorb water
response to water shortages?
Which part of a plant absorbs most of the water and minerals taken up
root hairs
from the soil?
An evolutionary adaption that increases exposure of a plant to light in
apical dominance
a dense forest is....
A person working with plants may remove apical dominance by...
pruning
Land plants are not composed of what tissue?
mesodermal tissues.
Vascular plant tissue includes all of the following cell types except
cambium cells
What functional plant cells lack a nucleus?
xylem and sieve-tube cells
Long, thin tapered cells with lignified cell walls that function in
sclerenchyma
support and permit water to flow through pits
Living cells that lack nuclei and ribosomes: they transport sugars and
sieve cells
other organic nutrients
The least specialized plant cells, which serve general metabolic,
Parenchyma
synthetic, and storage functions
Cells with unevenly thickened primary walls hat support stillCollenchyma
elongating parts of the plant
Mature cells without protoplasts with thick, lignified secondary walls
Sclerenchyma
that may not function in transport
Which of the following is not a characteristic of parenchyma cells?
Have secondary thickenings
Which of the following tissues is incorrectly matched with its
collenchyma- uniformly thick-walled
characteristics?
supportive tissues
The fiber cells of plants are a type of
sclerenchyma
The vascular bundle in the shape of a single central cylinder root is
stele
called
One important difference between the anatomy of roots and the
a waxy cuticle covers leaves but is
anatomy of leaves is that..
absent in roots
the photosynthetic cells in the interior of a leaf are what kind of cells: parenchyma
A student examining leaf cross sections under a microscope finds
many loosely packed cells with relatively thin cell walls. The cells
Parenchyma
have numerous chloroplasts. What types of cells are these?
Secondary growth is produced by both
Which of the following is true about secondary growth in plants?
the vascular cambium and the cork
cambium
A friend has discovered a new plant and brings it to you to classify. h
eplant has the following characteristics a taproot system with growth
Woody eudicot
rings evident in cross section and a layer of bark around the outside. It
is?
cell elongation localized in each
Shoot elongation in a growing bud is due primarily to..
internod
Axillary buds develop from
meristematic cells left by the apical
meristem
Gas exchange, necessary for photosynthesis, can occur most easily in
spongy mesophyll
which leaf tissue?
root cap, apical meristem, zone of cell
What is the correct sequence from the growing tips of the root
division, zone of elongation, and zone of
upward?
maturation
Which of the following is incorrectly paired with its structure and
Pericycle- waterproof ring of cells
function?
surrounding the stele in roots
Which of the following root tissues gives rise to lateral roots?
Pericycle
Pores on the leaf surface that function in gas exchange are called:
stomata
Which of the following is a true statement about growth in plants
some plants secondary growth
Which of the following cell types are correctly matched with their
companion cell-formation of secondary
functions except...
xylem and phloem
What tissue makes up most of the wood of a tree?
secondary xylem
3 rings of the xylem and 1 rings of the
The vasclar system of a three-year-old eudicot stem consists of
phloem
Which of the following is true of bark?
It is composed of phloem plus periderm.
Suppose Geroge completely removed the bark from around the base of
a cherry tree but was stopped by his father before cutting the tree
xylem
down. Plant lived for several weeks but then died. What tissue was
left?
Additional vascular tissue produced as secondary growth in a root
vascular cambium
originates from which cells?
Before differentiation can begin during the process of plant cell and
undergo differentiation
tissue culture, parenchyma cells from the source tissue must
In leaves, chloroplasts are found in
palisade mesophyll
------- provides cells for secondary growth.
Vascular cambium
Secondary grrowth never occurs in
leaves
How is he supply of vascular cambium maintained?
Through the division of cells
Which structure is incorrectly paired with its tissue?
companion cell-ground tissue
Wood consists of
secondary xylem.
Which of the following is not part of an older tree's bark?
secondary xylem
Secondary xyelm, leaves, trichomes,
Which of the following arises from meristematic activity
and tubers (all of the above)
------ is to xylem as ---- is to phloem.
vessel element; sieve-tube member.
The driving force that pushes the root tip through the soil is due
elongation of cells behind the root apical
primarily to:
meristem.
------ provides cells for primary growth
apical meristems
Ch 36 Transport in Vascular Plants
Question
Answer
Which of the following would least likely to affect osmosis in plants? receptor proteins in the membrane
slow movement through the lipid bilayer
Active transport involves all of the following except the
of a membrane
Like many plants process, transport of various material in plans at the
xylem membranes
cellular level requires all of the following except:
flow of water out of a cell, flow of water
Which of the following is an example of osmosis?
between cells
The amount and direction of movement of water in plants can always
water potential
be predicted by measuring which of the following?
Which of the following is true concerning the water potential of a
It is equal to zero when the cell is in
plant cell?
pure water and is turgid.
Your laboratory partner has an open beaker of pure water. By
zero
definition, the water potential of this water is?
air pressure, water-attracting matrices
Which of the following has an effect on water potential in plants?
and dissolved solutes
If Wp =.3 MPa and Ws = -.45 then this equals
-.15 MPa
The value for water potential in a root was found to be -.15 MPa. If
you take the tissue and place it in a solution of sucrose with a -.23,
from the tissue into the sucrose
water will flow where?
COmpared to a cell with a few aquarporins in its membrane, a cell
have a faster rate of osmosis
containing many aquaporins will...
Some botanists agree tha the entire plant should be considered a single
unit rather than a composite of may individual cells. Which of the
tonoplast
following cellular structures cannot be used to support this view?
It depends on the force of gravity on a
Which of the following statements is false about bulk flow?
column of water.
It transports mainly sugars and amino
Which of the following statements about xylem is incorrect?
acids
Which of the following would likely not contribute to the surface area endodermis (they are water resistant and
available for water absorption from the soil by a plant root system?
waxy)
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 form the soil
It ensures that all water and dissolved
In plant roots, the casparian e strip is correctly described by which of
substance must pass through a cell
the following?
before entering the stele
All of the following describe an important component of the longendodermis Casparian strip
distance transport process in plants except
the normal symbiotic fungi are not
Pine seedlings grow in sterile potting soil grow much slower than
present in the sterilized soil and water
seedlings grown in soil from the are where the seeds were collected.
and mineral uptake is faster when
This is most likely because:
mycorrhizae are present.
A water molecule could move all the way through a plant from soil to
the endodermis
root to leaf to air and pass through a living cell only once. this living
cell would be part of what structure?
The following factos may sometimes play a role int he movement of
sap through the xylem. Which one depends on the direct expenditure
of ATP by the plant?
What is the main cause of guttation in plants
One is the most likely to see guttation in small plants when the..
What is the main force by which most of the water within xylem
vessels moves toward the top of a tree?
In which plant cell or tissue would the pressure component of water
potential most often be negative?
Water potential is generally most negative in which of the following
part of a plant?
Which of the following has the lowest (most negative) water
potential?
Which of the following is responsible for the cohesion of water
molecules
concentration of ions in the symplast
root pressure
root pressure exceeds transpiration pull
evaporation of water through the stoma
stem xylem
mesophyll cells of the leaf
leaf air spaces
hydrogen bonds between the oxygen
atom of one water molecule and a
hydrogen atom of another water
molecule
Active transport would be least important in the normal functioning of
stem xylem
which of the following plant tissue types?
help balance the photosynthesisGuard cells do which of the following?
transpiration compromise
All of the following normally enter the plant through the roots except: carbon dioxide
stomata close, preventing CO2 entry
Photosynthesis begins to decline when leaves wilt because
into the leaf
The water lost during transpiration is an unfortunate side effect of the
plant's exchange of gases. However, the plant derive some benefit
evaporative cooling and increased turgor
from this water loss in the form of..
Ignoring all other factors, what kind of day would result in the fastest
warm, dry day
delivery of water and minerals to the leaves of a tree?
If the guard cells and surrounding cells in a plant are deficient in
leaf temperatures would decrease
potassium ions, all of the following would occur except..
an increase in the osmotic concentration
The opening of stomata is thought to involve...
of the guard cells
Which of the following experimental procedures would most likely
Increasing the level of carbon dioxide
reduce transpiration while allowing the normal growth of a plant?
around the plant.
All of the following are adaptation that help reduce water loss from a
transpiration
plant except..
Phloem transport of sucrose can be describe as going from "source to
mature leaf
sink". Which of the following would not normally function as a sink?
Which of the following is a correct statement about sugar movement Movement can occur both upward and
in phloem?
down in the plant.
Phloem transport is described as being from source to sink. Which of
Phloem transports sugars from the leaf
the following would most accurately complete this statement about
source to the apical meristem sink.
transport? Phloem transport --- from the --- source to the--- sink.
Explain the mass flow of materials in the phloem?
Water flows into the source end of a sieve tube because
Which one of the following statements about transport of nutrients in
phloem is false?
According to the pressure flow hypothesis of phloem transport,
Which of these involves a symbiotic relationship?
------ increase the surface area of roots.
In roots the ------- forces water and solutes through the plasma
membranes of the ----- cells before entering the -------.
Sugars move from leaves into the ------ of ----- by ------.
The water pressure that pulse water and sugar from sugar source to
sugar sink is referred to as ----.
Transpiration in plants requires all of the following except
Which of the following is an advantage of tracheids over vessels for
long-distance transport to great heights?
Guard cells are the only cells in the epidermis that contain
chloroplasts and can undergo photosynthesis. This is important
because...
leaf cells produce sugar by
photosynthesis; Sugar is transported
from cell to cell in the leaf; Solutes are
actively transported into sieve tubes;
water diffuses into the sieve tubes;
sugars moves down the stem
sucrose has been actively transported
into the sieve tube, making it hypertonic
Companion cells control the rate and
direction of movement of phloem sap.
solute move from a high concentration
in the "source" to a lower concentration
in the "sink"
mycorrhizae
Root hairs and mycorrhizae
Casparian strip; endodermis; xylem
Sugars move from leaves into the sievetube members of the phloem by active
transport.
bulk flow
active transport through xylem cells.
Adhesive forces are proportionally
greater in narrower cylinders than in
wider cylinders and Cohesive forces are
greater in narrow tubes than in wide
tubes of the same height.
ATP is required to power proton pumps
in the guard cell membranes.
Ch 37 Plant Nutrition
Question
Which of the following describes the fate of most of the water taken up
by a plant?
Most of the dry weight of a plant is the result of uptake of:
Organic molecules make up what percentage of the dry weight of a
plant?
In hydroponic culture, what is the purpose of bubbling air into the
solute?
Which two elements make up more than 90% of the dry weight of
plants?
The bulk of a plant's dry weight is derived from...
What are the three main elements of which plant growth and
development depend?
Which of the following elements is incorrectly paired with its function in
a plant?
In the nutrition of a plant, which element is classified as a
macronutrient?
Reddish-purple coloring of leaves, especially along the margins of
young leaves, is a typical symptom of deficiency of which element?
Answer
It is lost during transpiration
CO2 through stomata in leaves
96%
to provide oxygen to root cells
oxygen and carbon
CO2
oxygen, carbon, hydrogen
sulur- component of DNA; activates some
enzymes
calcium
P
Which of the following is not true of micronutrients in plants?
They are essential elements of small size
and molecular weight.
A growing plant exhibits hclorosis of the leaves of the entire plant. The
chlorosis is probably deficiency of which of the following
macronutrients?
nitrogen
What is meant by the term chlorosis?
the yellowing of leaves due to decreased
production
Iron deficiency is often indicated by chlorosis in newly formed leaves.
This suggests that ...
A soil well suited for the growth of most plant would have all the
following properties except ...
What soils is are the most fertile...
Why does overwatering a plant kill it?
What should be added to soil to prevent minerals from leaching away?
The N-P-K percentages on a package of fertilizer refer to the...
A young farmer purchases some land in a relatively arid area and is
interested in earning a reason profit for many years. which of the
following strategies would best allow such a goal to be achieved?
A farming commitment that embraces a variety of methods that are
conservation-minded, environmentally safe, and profitable...
An early use of indicator plants (plants that tolerate high levels of heavy
metals in the soil) was to locate potential profitable areas to mine for
those minerals. A current use for such plants is:
Nitrogen fixation is a process that..
Why is nitrogen fixation such an important process?
iron is an immobile nutrient in plants
a high pH
both humus and loam.
The roots drowned (cannot get air)
humus
percentages of three important mineral
nutrients.
selecting crops adapted to arid areas
sustainable agriculture
bioremediation to help clean up mine soils.
converts nitrogen gas to ammonia.
fixed nitrogen is most often the limiting
In what way do nitrogen compounds differ from other minerals needed
by plants?
Most crop plants acquire their nitrogen mainly in the form of...
The enzyme complex nitrogenase catalyzes the reaction that reduces
atmospheric nitrogen to...
The most efficient way to increase essential amino acids in crop plants
for human consmption...
Among important crop plants, nitrogen-fixing root nodules are most
commonly an attribute of ...
If a legume is infected with rhizobium, what is the probable effect on the
plant?
factor in plant growth
Only nitrogen requires the action of
bacteria to be made available to plants.
NO3NH3
breed for higher yield of deficient amino
acids.
legumes
It obtains nitrogen from nitrogen fixation.
You are weeding your garden when you accidentally expose some roots.
You notice swellings (root nodules) on the roots. Most likely your plant is benefiting from a mutualistic bacterium.
..
Flavonoids trigger gene-regulating protein
How do legume plant roots communicate Rhizobium bacteria..
in bacterium.
A woodlot was sprayed with a fungicide. What would the most serious a decrease in tree growth due to death
effect on such spraying
mycorrhizae
What is the mutualistic association between roots and fungi called?
mycorrhizae
Hyphae form a covering over roots. Altogether hyphae create a large
aid in absorbing minerals and ions
surface area and do which of the following?
Ectomycorrhizae do not penetrate root
Which of the following is a primary difference between ectomycorrhizae
cells, whereas endomycorrhizae grow into
and endomycorrhizae?
invaginations of the root cell membranes.
The earliest vascular plants on land had underground stems (rhizomes)
absorption by symbiotic fungi
but no roots. Water and mineral nutrients were most likely obtained by...
Dwarf mistletoe grows on many pine trees in the Rockies. Although the
mistletoe is green, it is probably not sufficiently active in photosynthesis
a parasite.
to produce all the sugar it needs. The mistletoe also produces haustoria.
So it is best classified as
plants that grow on other plants but do not
What are epiphytes?
obtain nutrients from their hosts
Carnivorous plants have evolved mechanisms that trap and digest small
animals. The products of this digestion are used to supplement the
plant's supply of ...
What process is the source of the CO2 that root hairs release into the
soil?
Roots expend ATP to pump ________ ions from the root to the soil and
by doing so displace mineral ions bound to soil particles.
Acid precipitation..
Denitriifying bacteria covert ------- to -------.
minerals
cellular respiration
H+
decreases soil fertility
nitrates: nitrogen gas
Ch 38 Angiosperm Reproduction
Question
Answer
The products of meiosis in plants are always which of the following? spores
Which of the following is the correct sequence during alternation of
generations in a flowering plant?
sporophyte-meiosis-gametophyte-gametes-fertilizationdiploid zygote
Which of the following is true in plants?
Meiosis occurs in sporophytes to produce spore
All of the following are features of angiosperms except:
a small (reduced) sporophyte
Based on studies of plant evolution, which flower is not a modified
leaf?
receptacle
All of the following floral parts are directly involved in pollination
except the:
sepal
Floral parts would have the greatest impact on pollination?
Sepal or Petal
A mutation in which of the following floral parts would have the
greatest potential impact on fertilization?
Stamen or carpel
Which of the following is the correct order of floral organs from the
outside to the inside of a complete flower?
sepals, petals, stamens, carpels.
All of the following are primary functions of flowers except:
photosynthesis
Meiosis occurs within all of the following flower parts except the...
style
A perfect flower is fertile but may be either complete or incomplete.
Which of the following correctly describes a perfect flower?
It has both stamen and carpels.
Carpellate flowers..
develop into fruits
which of the following types of plants is not able to self-pollinate?
dioecious.
In flowering plants, pollen is released from the ...
anther
In the life cycle of an agiosperm, which of the following stages is
diploid..
microsporocyte
Where does meiosis occur in flowering plants?
megasporocyte and microsporocyte
Which of the following is a correct sequence of processes that takes
place when a flowering plant reproduces?
meiosis, pollination, nuclear fusion, formation of embryo
and endosperm
Which of these is incorrectly paired with its life-cycle generation?
anther- gametophyte
Which of the following is the correct sequence of events in a pollen
sac?
microsporocyte-meiosis-microspores-mitosis-two
haploid cells per pollen grain
Which of the following occurs in an angiosperm ovule?
A megaspore mother cell undergoes meiosis.
Where and by which process are sperm produced in plants?
Mitosis in male gametophytes
In which of the following pairs are the two terms equivalent?
embryo sac -- female gametophyte
Which of the following is the male gametophyte of a flowering plant? pollen grain
In flowering plants, a mature male gametophyte contains...
two sperm nuclei and one tube cell nucleus.
Within the female gametophyte, three mitotic divisions of the
megaspore produce..
three antipodal cells, two polar nuclei, one egg, and two
synergids
The largest cell(s) of the typical angiosperm embryo sac is (are) the.. central cell
Which cells, after fertilization, give rise to the embryo plant?
egg cell
Which cells becomes the triploid endosperm?
polar nuclei
Which cells guide the pollen tube to the egg cell
tube cell
What is the relationship between pollination and fertilization in
plants?
Pollination brings gametophytes together so that
fertilization can occur
Recent research has shown that pollination requires that carpels
recognize pollen gains as "self or non self". For self-incompatibility, the rejection of self cells
the system requires
As flowers develop, which transition does not occur?
The tube nucleus becomes a sperm nucleus.
The integuments of an ovule function to do what?
form a seed coat
A fruit includes
one or more seeds and has fleshy cells rich in sugars.
What is typically the result of double fertilization in angiosperms?
Both a diploid embryo and a triploid endosperm are
formed.
Which of the following statements regarding the endosperm is false? It develops from the fertilized egg.
In angiosperms, products of the terminal cell become the:
proembryo and the coteyledons
Which of the following statements is correct about the basal cell in a
It forms the suspensor that anchors the embryo.
zygote?
What is the embryonic root called?
radicle
Which of the following "vegetables" is botanically a fruit?
green beans
Which of these structures is unique to the seed of a monocot?
coleoptile
Which of the following statements about fruits is false?
Fruits form from microsporangia and integuments
Fruits develop from
ovaries
The first step in germination of a seed is usually
imbibition of water
When seeds germinate the radicle emerges before the shoot. This
allows the seedling to quickly...
obtain a dependable water supply
Which of the following is not true of the hypocotyl hook?
It is the first structure to emerge from a eudicot seed.
In plants, which of the following could be an advantage of sexual
reproduction as opposed to asexual reproduction?
genetic variation
Which of the following is true about vegetative reproduction?
It produces clones.
Which of the following is a true statement about clonal reproduction Making cuttings of ornamental plans is a form of
in plants?
fragmentation.
All of the following could be considered advantages of asexual
reproduction in plants except..
adaptation of change.
Which of the following statements is true of protoplast fusion?
It can be used to form new plant varieties by combining
genomes from two plants.
Which of the following statements is correct about protoplast fusion? It can be used to form new plant species.
The most immediate potential benefits of introducing genetically
modified crops include..
increasing crop yield.
The monetary costs of growing genetically modified
Which of the following is not a scientific concern relating to creating
plants are significantly greater than traditional breeding
genetically modified crops?
techniques.
Currently available transgenic plants have been modified for all of
the following traits except..
nitrogen fixation.
Flowers are made of modified..
leaves
Which of these is unique to the flowering plants?
double fertilization.
What is endosperm?
a food-storing tissue of the seed
________ is the first event in seed formation
pollination.
Which of the following statements is true about transgenic plants?
They contain genes from more than one species.
Ch 39 Plant Response to Internal and External Signals
Question
Answer
The step(s) between a plant's perception of a change in the
environment and the plant's response to that change is (are) best
signal transduction
called..
Plants adjust their growth and development in
Which of the following statement is (are) true of plants?
response to environmental cues.
External stimuli would be received most quickly by a plant cell if the
cell membrane.
receptors for signal transduction were located in the...
Secondary messengers are associated with which of the following?
transduction
Having each receptor molecule produce
In a signal transduction pathway, the transduction stage amplifies the multiple secondary messengers and having
original signal by...
each secondary messenger activate numerous
specific enzymes.
What would happen if the secondary messenger cGMP was blocked Ca 2+ channels could open, and specific
in the de-etiolation pathway?
protein kinase 2 could still be produced
If protein synthesis was blocked in eitiolated cells, what would be
post-translational modification of existing
necessary for any de-etiolation to occur?
proteins
Charles and Francis Darwin concluded from their experiments on
photropism by grass seedlings that the part of the seedling that
tip of the coleoptile.
detects the direction of light is the...
Pants growing in a partially dark environment will grow toward light
Auxin causes a decrease in growth on the side
in a response called phototropism. Choose the incorrect statement
of the stem exposed to light.
regarding phototropism:
Which of these conclusions is supported by the research of both Went A chemical substance involved in shoot
and Charles and Frances Darwin on shoot responses to light?
bending is produced in shoot tips.
We know from the experiments of the past that plants bend toward
cell expansion is greater on the dark side of
light because
the stem.
Plant hormones can be characterized by all of the following except
function independently of other hormones
that they:
All of the above make the study of plant
Why is it so difficult to study the actions of plant hormones?
hormones difficult.
auxin can stimulate cell elongation in apical
Plant hormones can have different effects at different concentrations.
meristems, yet will inhibit the growth of
This explains how ...
axillary buds.
Which plant hormones might be used to enhance stem elongation and
auxins and gibberellins.
fruit growth?
increasing wall plasticity and allowing the
According to the acid growth hypothesis, auxin works by..
affected cell wall to elongate.
Which of the following hormones would be most useful in promoting
auxins
the rooting of plant cuttings?
Which plant hormone(s) is (are) most closely associated with cell
cytokinin
division?
One effect of gibberellins is to stimulate cereal seeds to produce ...
amylase
In attempting to make a seed break dormancy, one logically could
gibberellins.
treat it with..
Both and red and blue light are involved in...
stem elongation.
Most plants close their stomata at night. What color of light would be
most effective in promoting stomatal opening in the middle of the
blue
night?
The biological clock controlling circadian rhythms must ultimately ...
Plants often use changes in day length (photoperiod) to trigger events
such as dormancy and flowering. It is logical that plants have evolved
this mechanism because photoperiod changes:
Plants often use changes in day length (photoperiod) to trigger events
such as dormancy and flowering. It is logical that plants have evolved
this mechanism because photoperiod changes:
A botanist exposed two groups of the same plant species to two
photoperiods-one with 14 hours of light and 10 hours of dark and the
other with 10 hours of light and 14 hours of dark. Under the first set
of conditions, the plants flowered, why?
In order to flower, a short-day plant needs a..
A long-day plant is if..
affect gene transcription.
are more predictable than air temperature
changes.
are more predictable than air temperatures.
The plants flower in the spring.
night that is longer than certain length.
the duration of continuous darkness is less
than a critical length
Plants that have their flowering inhibited by being exposed to bright
short-day plants.
lights at night are:
If you take a short-day plant and put it in a lab under conditions
where it will flower (long nights and short days), but interrupt its day It will flower.
period with a few minutes of darkness, what will happen?
Florigen is a flowering signal, not yet chemically identified, found in: leaves.
What do results of research on gravitropic responses of roots and
stems show?
If you wanted to genetically engineer a plant to be more resistant to
drought, increasing amounts of which of the following hormones
might be a good first attempt?
The initial response of the root cells of a tomato plant watered with
seawater would be to..
Plants are affected by an array of pathogens. Which of the following
is not a plant defense against disease?
The breakdown of chlorophyll reveals the ________ pigments of a
leaf...
The protective layer that forms between the abscission layer and the
stem consists of ...
After leaf abscission, growth will resume from the..
What is the specific term that refers to seasonal changes in the
relative lengths of night and day?
Day-neutral plants flower regardless of...
Which hormone is incorrectly paired with its function?
Buds and sprouts often form on tree stumps. Which of the following
hormones would you expect to stimulate their formation?
How might a plant respond to severe heat stress?
The effect of a plant hormone can depend on
the tissue.
abscisic acid
begin to plasmolyze as water is lost.
All of the above are plant defenses against
disease.
carotenoid
weak, colorless, thin-walled cells.
petiole
photoperiod
day length, night length, or photoperiod.
cytokinins—initiate programmed cell death
cytokinins
By producing heat-shock proteins, which may
protect the plants proteins from denaturing.