chapter 23: plant structure and function · contrast the structures and func-tions of parenchyma,...
TRANSCRIPT
604
What Yoursquoll Learn You will describe and compare
the major types of plant cellsand tissues
You will identify and analyzethe structure and functions ofroots stems and leaves
You will identify plant hor-mones and determine thenature of plant responses
Why Itrsquos ImportantHumans and the organismsaround them including plantsshare an environment By know-ing about plant structure andhow plants function you canbetter understand how humansand plants interact
Plant Structure and Function
Plant Structure and Function
David SierenVisuals Unlimited
Visit tobull study the entire chapter onlinebull access Web Links for more
information and activities onplant structure and function
bull review content with theInteractive Tutor and self-check quizzes
These pitcher plants look differ-ent from the plants that sur-round them However they andthe other plants have similarplant systems and subsystems
Understandingthe Photo
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231 PLANT CELLS AND TISSUES 605
Types of Plant Cells Like all organisms plants are composed of cells Plant cells are different
from animal cells because they have a cell wall a central vacuole and cancontain chloroplasts Figure 231 shows a typical plant cell Plants just likeother organisms are composed of different cell types
ParenchymaParenchyma (puh RENG kuh
muh) cells are the most abundantkind of plant cell They are foundthroughout the tissues of a plantThese spherical cells have thinflexible cell walls Most parenchymacells usually have a large centralvacuole which sometimes containsa fluid called sap
Chloroplast
Central vacuole
Cell wall
Plant Cells and Tissues
Figure 231 Plant cells have several distinguishingfeatures such as a cell wall chloro-plasts and a large central vacuole
SECTION PREVIEWObjectivesIdentify the major typesof plant cellsDistinguish among thefunctions of the differenttypes of plant tissues
Review Vocabularyvacuole membrane-bound
fluid-filled space in thecytoplasm of cells usedfor the temporary stor-age of materials (p 183)
New Vocabularyparenchymacollenchymasclerenchymaepidermisstomataguard celltrichomexylemtracheidvessel elementphloemsieve tube membercompanion cellmeristemapical meristemvascular cambiumcork cambium
231
Plants Cells and Tissues Make the following Foldable to help you compare the types of plant cells and tissues
Plantcells
Plant tissues
Identify and Describe As you read Chapter 23 identify and describe the types of plant cells and plant tissues under each tab
Fold a vertical sheet of paper in half from top to bottom
Fold in half from side to side with the fold at the top
Unfold the paper once Cut only the fold of the top flap to make two tabs
Turn the paper vertically and label the front tabs as shown
STEP 1
STEP 3
STEP 2
STEP 4
Objective 402 Analyze the processes by which organisms rep-resentative of the following groups accomplish essential life functions including hellipnon vascular plants gymnosperms and angiosperms Transport excretion respiration regulationnutrition synthesis reproduction growth and development
North Carolina Objectives
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Parenchyma cells as shown inFigure 232A have two main func-tions storage and food productionThe large vacuole found in these cellscan be filled with water starch grainsor oils The edible portions of manyfruits and vegetables are composedmostly of parenchyma cells Paren-chyma cells also can contain numer-ous chloroplasts that produce glucoseduring photosynthesis
Collenchyma
Collenchyma (coh LENG kuh muh)cells are long cells with unevenlythickened cell walls as illustrated inFigure 232B The structure of thecell wall is important because it allowsthe cells to grow The walls of col-lenchyma cells can stretch as the cellsgrow while providing strength andsupport These cells are arranged intubelike strands or cylinders that pro-vide support for surrounding tissueThe long tough strands you may havenoticed in celery are composed of collenchyma
SclerenchymaThe walls of sclerenchyma (skle
RENG kuh muh) cells are very thickand rigid At maturity these cellsoften die Although their cytoplasmdisintegrates their strong thick cellwalls remain and provide support forthe plant Sclerenchyma cells can beseen in Figure 232C Two types ofsclerenchyma cells commonly foundin plants are fibers and sclerids (SKLER
idz) Fibers are long thin cells thatform strands They provide supportand strength for the plant and are thesource of fibers used for making linenand rope A type of fiber is associatedwith vascular tissue which you willlearn about later in this sectionSclerids are irregularly shaped andusually found in clusters They arethe gritty texture of pears and a majorcomponent of the pits found inpeaches and other fruits
Compare and contrast the structures and func-tions of parenchyma collenchymaand sclerenchyma
606 PLANT STRUCTURE AND FUNCTION
par- from theGreek word parameaning ldquobesiderdquocoll- from theGreek word kollameaning ldquogluerdquoscler- from theGreek wordskleros meaningldquohardrdquo Parenchyma col-lenchyma and sclerenchyma areall types of planttissues
Figure 232Plants are composed ofthree basic types ofcells which are shownhere stained with dyes
Parenchyma cells are foundthroughout a plant Because theircell walls are flexible parenchymacells can have different shapes
A Collenchyma cells often are foundin parts of the plant that are stillgrowing Notice the unevenlythickened cell walls
B The walls of sclerenchyma cellsare very thick These dead cellsare able to provide support forthe plant
C
LM Magnification 120LM Magnification 54 LM Magnification 80
(bl)Jack M BostrackVisuals Unlimited (bc)Ken WagnerPhototake NYC (br)Biophoto AssociatesScience Photo LibraryPhoto Researchers
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607
Plant TissuesRecall that a tissue is a group of cells
that function together to perform anactivity Tissues can be referred to asplant subsystems There are several dif-ferent tissue types in plants
Dermal tissuesThe dermal tissue or epidermis is
composed of flattened cells that coverall parts of the plant It functionsmuch like the skin of an animal cov-ering and protecting the body of aplant As shown in Figure 233 thecells that make up the epidermis aretightly packed and often fit togetherlike a jigsaw puzzle The epidermalcells produce the waxy cuticle thathelps prevent water loss
Another structure that helps con-trol water loss from the plant a stomais part of the epidermal layer Stomata(STOH mah tuh) (singular stoma) areopenings in leaf tissue that control theexchange of gases Stomata are foundon green stems and on the surfaces ofleaves In many plants fewer stomataare located on the upper surface of theleaf as a means of conserving waterCells called guard cells control theopening and closing of stomata The
opening and closing of stomata regu-lates the flow of water vapor from leaftissues You can learn more aboutstomata in the BioLab at the end of thischapter
The dermal tissue of roots mayhave root hairs Root hairs are exten-sions of individual cells that help theroot absorb water and dissolved min-erals On the stems and leaves ofsome plants there are structurescalled trichomes Trichomes (TRI
kohmz) are hairlike projections thatgive a stem or a leaf a ldquofuzzyrdquo appear-ance They help reduce the evaporationof water from the plant In somecases trichomes are glandular andsecrete toxic substances that help pro-tect the plant from predatorsStomata root hairs and trichomesare shown in Figure 234
Figure 233 The cells of the epider-mis fit together tightlywhich helps protect theplant and preventswater loss
Figure 234 A root hair (A) is an extension of a root epidermal cell A trichome (B) isunicellular or multicellular growth from an epidermal cell Stomata (C)are openings in the leaf epidermis Each stoma is surrounded by twoguard cells
Color-enhanced SEM Magnification 200
Stained LM Magnification 100
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Color-enhanced SEMMagnification 63
Color-enhanced SEM Magnification 715
Mic
rofil
ed S
cien
tific
LT
DS
cien
ce P
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Lib
rary
Pho
to R
esea
rche
rs (
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arry
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unk
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nt H
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Vascular tissuesFood dissolved minerals and
water are transported throughout theplant by vascular tissue Xylem andphloem are the two types of vasculartissues Xylem is plant tissue com-posed of tubular cells that transportswater and dissolved minerals from theroots to the rest of the plant In seedplants xylem is composed of fourtypes of cellsmdashtracheids vessel ele-ments fibers and parenchyma
Tracheids (TRA kee uhdz) aretubular cells tapered at each end Thecell walls between adjoining tracheidshave pits through which water anddissolved minerals flow
Vessel elements are tubular cellsthat transport water throughout theplant They are wider and shorter thantracheids and have openings in theirend walls as shown in Figure 235 Insome plants mature vessel elementslose their end walls and water and dis-solved minerals flow freely from onecell to another
Although almost all vascular plantshave tracheids vessel elements aremost commonly found in anthophytesConifers have tracheids but no vesselelements in their vascular tissuesThis difference in vascular tissuescould be one reason why anthophytesare the most successful plants on Earth Anthophyte vessel elements arethought to transport water more effi-ciently than tracheids because watercan flow freely from vessel element tovessel element through the openings intheir end walls
You can learn more about vasculartissues in the MiniLab on this pageWhat other types of tissues are foundin vascular plants To answer thisquestion look at Figure 236 on thenext page
Sugars and other organic com-pounds are transported throughout avascular plant within the phloem
608 PLANT STRUCTURE AND FUNCTION
Figure 235Tracheids and vessel elements are the conductingcells of the xylem These cells die when theymature but their cell walls remain
Tracheid
Vessel element
ObserveExamining Plant Tissues Pipes arehollow Their shape or structure allowsthem to be used efficiently in trans-porting water Plant vascular tissueshave this same efficiency in structure
Procedure Snap a celery stalk in half and remove
a small section of ldquostringy tissuerdquo from itsinside
Place the material on a glass slide Add several drops ofwater Place a second glass slide on top CAUTION Usecaution when handling a microscope and glass slides
Press down evenly on the top glass slide with your thumbdirectly over the plant material
$ Remove the top glass slide Add more water if neededAdd a coverslip
Examine the celery material under low-and high-powermagnification Diagram what you see
^ Repeat steps 2ndash5 using some of the soft tissue inside thecelery stalk
Analysis1 Describe Write a description of the stringy tissue under
low- and high-power magnification2 Describe Write a description of the soft tissue under
low- and high-power magnification3 Explain Does the structure of these tissues suggest their
functions
EnvisionGeorge Mattei
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A Plantrsquos Body PlanFigure 236There seems to be an almost endless variety ofvascular plants Regardless of their diversity andnumerous adaptations all vascular plants havethe same basic body plan They are composed ofcells tissues and organs Critical Thinking Whatare the different types of meristems andhow do they help produce new plant systems and subsystems
231 PLANT CELLS AND TISSUES 609
Apical meristem
Leaves
Vascular tissues
Stem
Apical meristems
Cells Most new plant cells are produced by cell divisions in regions of a plant calledmeristems Meristematic cells continuallydivide After each cell division one of the two new cells remains meristematic and the other begins to differentiate Two types of meristemsmdashapical and lateralmdashproducedifferent cell types Apical meristems producecells that add length to stems and rootsLateral meristems produce cells that increasestem and root diameters
AA
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Vascular plants
Tissues Plants have four types of tissuesdermal vascular ground and meristematicDermal tissues cover the plant body Vasculartissues transport water food and dissolvedsubstances throughout the plant Photosynthesisstorage and secretion are functions of groundtissue Meristematic tissues produce most of aplantrsquos new cells
Organs The major plant organs are stems leaves androots They differ in structure among plant divisions butshare common functions A stem is a plant organ thatprovides structural support and contains vascular tissuesLeaves and reproductive structures grow from stemsUsually leaves are the organs in which photosynthesisoccurs Leaf form differs among plants Roots anchor aplant in soil or on another plant or structure Most rootsabsorb water and dissolved substances that then aretransported in vascular tissues throughout the plant
Hans ReinhardOKAPIAPhoto Researchers
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Phloem is made up of tubular cellsjoined end to end as shown in Figure 237 It is similar to xylembecause phloem also has long cylin-drical cells However these cellscalled sieve tube members are aliveat maturity Sieve tube members areunusual because they contain cyto-plasm but do not have a nucleus orribosomes Next to each sieve tubemember is a companion cellCompanion cells are nucleated cellsthat help with the transport of sugarsand other organic compoundsthrough the sieve tubes of thephloem In anthophytes the end wallsbetween two sieve tube members arecalled sieve plates The sieve plateshave large pores that allow sugar andorganic compounds to move fromsieve tube member to sieve tubemember Phloem can transport mate-rials from the roots to the leaves alsoYou can learn more about vascular tis-sues in Problem-Solving Lab 231
The vascular phloem tissue ofmany plants contains fibers Althoughthe fibers are not used for transportingmaterials they are important becausethey provide support for the plant
Ground tissueGround tissue is composed mostly
of parenchyma cells but it may also include collenchyma and scle-renchyma cells It is found through-out a plant and often is associatedwith other tissues The functions ofground tissue include photosynthesisstorage and support The cells ofground tissue in leaves and somestems contain numerous chloroplaststhat carry on photosynthesis Groundtissue cells in some stems and rootscontain large vacuoles that storestarch grains and water Cells such asthose shown in Figure 238 are oftenseen in ground tissue
Companion cell
Sieve plate
Sieve tube member
Figure 237 Phloem tissue carries sugars and other organic compounds throughoutthe plant
Figure 238 The numerous chloroplasts in this ground tissue produce food for the plant
610 PLANT STRUCTURE AND FUNCTION
Chloroplasts Color-enhanced LMMagnification 400
Michael EichelbergerVisuals Unlimited
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Meristematic tissuesA growing plant produces new cells
in areas called meristems Meristemsare regions of actively dividing cellsMeristematic cells are differentlyshaped parenchyma cells with largenuclei There are several types ofmeristems two types are shown inFigure 236 on page 609
Apical meristems are found at ornear the tips of roots and stems Theyproduce cells that allow the roots andstems to increase in length Lateralmeristems are cylinders of dividingcells located in roots and stems Theproduction of cells by the lateralmeristems results in an increase inroot and stem diameters Most woodyplants have two kinds of lateral meris-temsmdashvascular cambium and corkcambium The vascular cambiumproduces new xylem and phloem cellsin the stems and roots The corkcambium produces cells with toughcell walls These cells cover the sur-face of stems and roots The outerbark of a tree is produced by the corkcambium
A third type of lateral meristem isfound in grasses corn and othermonocots This meristem adds cellsthat lengthen the part of the stembetween the leaves These plants donot have a vascular or a cork cambium
Understanding Main Ideas1 Describe the distinguishing characteristics of the
three types of plant cells2 Identify and analyze the function of vascular tissue
Name the two different types of vascular tissue3 Explain the function of stomata4 Draw a plant and identify and indicate where the
apical meristems would be located How do theyfunction differently from lateral meristems in thedevelopment of a plant
Thinking Critically5 Explain what type of plant cell you would expect
to find in the photosynthetic tissue of a leaf Whatis another name for the photosynthetic tissue
6 Compare and Contrast Compare and contrastthe cells that make up the xylem and the phloemFor more help refer to Compare and Contrast inthe Skill Handbook
SKILL REVIEWSKILL REVIEW
231 PLANT CELLS AND TISSUES 611
Apply ConceptsWhat happens if vascular tissue is interrupted Antho-phytes have tissues within their organs that transport materialsfrom roots to leaves and from leaves to roots What happens ifthis pathway is experimentally interrupted
Solve the ProblemA thin sheet of metal was insertedhalfway through the stem of a liv-ing tree as shown in the diagramOne day later the following analy-sis was madebull Concentration of water and dis-
solved minerals directly belowthe metal sheet was higher thanabove the metal sheet
bull Concentration of sugar directlyabove the metal sheet washigher than directly below themetal sheet
Thinking Critically1 Explain What is the function of phloem Why was the
concentration of sugars different on either side of themetal sheet
2 Explain What is the function of xylem Why was the con-centration of dissolved minerals and water different oneither side of the metal sheet
3 Analyze How would the experimental findings differ if themetal sheet were inserted only into the bark of the tree
Higherwater anddissolved minerallevels
Highersugarlevels
Metalplate
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612 PLANT STRUCTURE AND FUNCTION
RootsRoots are plant organs that anchor a plant usually absorb water and
dissolved minerals and contain vascular tissues that transport materialsto and from the stem As shown in Figure 239 roots may be short orlong and thick and massive or thin and threadlike The surface area of aplantrsquos roots can be as much as 50 times greater than the surface area of
its leaves Most roots grow in soilbut some do not
The type of root system is geneti-cally determined but can varybecause of environmental factorssuch as soil type moisture and tem-perature There are two main typesof root systemsmdashtaproots andfibrous roots Carrots and beets aretaproots which are single thickstructures with smaller branchingroots Taproots accumulate and storefood Fibrous roots systems havemany small branching roots thatgrow from a central point
Some plants such as the corn inFigure 2310 have a type of root
Roots Stems and Leaves
(t)KS Studios (bl)Mark DouetTony Stone Images (br)John D CunninghamVisuals Unlimited
Figure 239 The taproot of a carrot plantcan store large quantities offood and water (A) The fibrousroots of grasses absorb waterand anchor the plant (B)
AA BB
232SECTION PREVIEWObjectivesIdentify and comparethe structures of rootsstems and leavesDescribe and comparethe functions of rootsstems and leaves
Review Vocabularyorgan group of two or
more tissues organizedto perform complexactivities within anorganism (p 210)
New Vocabularycortexendodermispericycleroot capsink translocationpetiolemesophyll transpiration
Do you like to eat plant organsUsing Prior Knowledge The next timeyou eat a salad look closely at its con-tents Did you know that most of theitems you are eating are plant organsLettuce and spinach are leaves Carrotsand radishes are roots Asparagus is astem Bean and alfalfa sprouts includeimmature leaves stems and roots Thereare more than one-quarter million kinds ofplants on Earth and their organs exhibit anamazing varietyExperiment After reading the first two sections of this chapter design an investigation to demonstrate how vascular tissue is common to roots stems and leaves Show your plan to yourteacher and get permission to perform the investigation Be sure to follow all labora-tory safety rules Share your findings with your class
Salad of rootsstems and leaves
Objective 402 Analyze the processes by which organisms representativeof the following groups accomplish essential life functions including hellipnon vascular plants gym-nosperms and angiosperms Transport excretion respiration regulation nutrition synthesis reproduction growth and development
North Carolina Objectives
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83122955
called prop roots which originateabove ground and help support a plantMany climbing plants have aerial rootsthat cling to objects such as walls andprovide support for climbing stemsWhen bald cypress trees grow inswampy soils they produce modifiedroots called pneumatophores whichare referred to as ldquokneesrdquo The kneesgrow upward from the mud and even-tually out of the water Knees helpsupply oxygen to the roots
The structure of rootsIf you look at the diagram of a root
in Figure 2311 you can see that aroot hair is a tiny extension of an epi-dermal cell Root hairs increase thesurface area of a root that contacts thesoil They absorb water oxygen anddissolved minerals The next layer is apart of the ground tissue called thecortex which is involved in the trans-port of water and dissolved mineralsinto the vascular tissues The cortex is
made up of parenchyma cells thatsometimes store food and water
At the inner limit of the cortex liesthe endodermis a layer of cells withwaterproof cell walls that form a sealaround the rootrsquos vascular tissues
Zea MaysVisuals Unlimited
Cortex
Epidermis
Root hair
EndodermisPericycle
Endodermalcells Waterproof
seal
Figure 2311Water and dissolved minerals moveinto the root along two pathways
Dissolved minerals and waterenter root hairs and travelthrough and between thecells of the cortex
Minerals dissolved in water can flowbetween the parenchyma cells directlyinto the root cortex then through thecells of the endodermis
Figure 2310As a corn plant growsprop roots grow from thestem and help keep thetall and top-heavy plantupright
232 ROOTS STEMS AND LEAVES 613
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The waterproof seal of the endodermisforces water and dissolved minerals thatenter the root to pass through the cellsof the endodermis Thus the endoder-mis controls the flow of water and dis-solved minerals into the root Next tothe endodermis is the pericycle It isthe tissue from which lateral roots ariseas offshoots of older roots
Xylem and phloem are located inthe center of the root The arrange-ment of xylem and phloem tissues asshown in Figure 2312 accounts forone of the major differences betweenmonocots and dicots In dicot rootsthe xylem forms a central star-shapedmass with phloem cells between the rays of the star Monocot rootsusually have strands of xylem thatalternate with strands of phloemThere is sometimes a central core ofparenchyma cells in the monocot rootcalled a pith
Root growthThere are two areas of rapidly divid-
ing cells in roots where the productionof new cells initiates growth The rootapical meristem produces cells that
614 PLANT STRUCTURE AND FUNCTION
pericycle from theGreek words perimeaning ldquoaroundrdquoand kykos meaningldquocirclerdquo In vascularplants the pericy-cle can producelateral rootsendodermis fromthe Greek wordsendon meaningldquowithinrdquo and dermis meaningldquoskinrdquo In vascularplants the endo-dermis is the inner-most layer of cellsof the root cortex
Runk-SchoenbergerGrant Heilman Photography
Figure 2313Roots develop by both cell division and elon-gation As the number and size of cellsincreases the root grows in length and width
Phloem
Pericycle
Endodermis
Root cap
Apical meristem
Root hairs
Xylem
Figure 2312The root structures of dicots andmonocots differ inthe arrangementof xylem andphloem
The xylem in this dicot root is arranged in acentral star-shaped fashion The phloem isfound between the points of the star
A In this monocot there are alternating strandsof xylem and phloem that surround a core ofparenchyma cells
B
Xylem
Phloem
Parenchyma
Stained LM Magnification 20 Stained LM Magnification 15
0612-0621 C23 S2 BDOL-829900 8404 1113 AM Page 614
cause a root to increase in length Asthese cells begin to mature they dif-ferentiate into different types of cellsIn dicots the vascular cambium devel-ops between the xylem and phloemand contributes to a rootrsquos growth byadding cells that increase its diameter
Each layer of new cells producedby the root apical meristem is left far-ther behind as new cells are addedand the root grows forward throughthe soil The tip of each root is covered by a protective layer ofparenchyma cells called the root capAs the root grows through the soilthe cells of the root cap wear awayReplacement cells are produced bythe root apical meristem so the roottip is never without its protective cov-ering Examine Figure 2313 on theprevious page to see if you can locateall the structures of a root
StemsStems usually are the aboveground
parts of plants that support leaves andflowers They have vascular tissuesthat transport water dissolved miner-als and sugars to and from roots andleaves Their form ranges from thethin herbaceous stems of basil plantsto the massive woody trunks of treesGreen herbaceous stems are soft andflexible and usually carry out somephotosynthesis Petunias impatiensand carnations are other examples ofplants with herbaceous stems Treesshrubs and some other perennialshave woody stems Woody stems arehard and rigid and have cork and vas-cular cambriums
Some stems are adapted to storingfood This can enable the plant tosurvive drought or cold or growfrom year to year Stems that act asfood-storage organs include cormstubers and rhizomes A corm is ashort thickened underground stem
surrounded by leaf scales A tuber is aswollen underground stem that hasbuds from which new plants cangrow Rhizomes also are undergroundstems that store food Some examplesof these food-storing stems are shownin Figure 2314
232 ROOTS STEMS AND LEAVES 615(t)JR WaalandiUniversity of WashingtonBPS (c)Image reprinted from The Visual Dictionary of Plants with permission from Dorling Kindersley Publishing (b)Robert amp Linda Mitchell
A white potato is a tuberA
This gladiolus cormis a thickenedunderground stemfrom which rootsleaves and flowerbuds arise
B
The rhizome ofan iris growshorizontallyunderground
C
Figure 2314 Plants can use food stored in stems to survivewhen conditions are less than ideal
0612-0621 C23 S2 BDOL-829900 8404 1113 AM Page 615
Internal structure Both stems and roots have vascular
tissues However the vascular tissues instems are arranged differently from thatof roots Stems have a bundled arrange-ment or circular arrangement of vascu-lar tissues within a surrounding mass ofparenchyma tissue As you can see inFigure 2315A and B monocots anddicots differ in the arrangement of vas-cular tissues in their stems In mostdicots xylem and phloem are in a circleof vascular bundles that form a ring inthe cortex The vascular bundles ofmost monocots are scattered through-out the stem
Woody stemsMany conifers and perennial dicots
produce thick sturdy stems as shownin Figure 2315C that may last severalyears or even decades As the stems ofwoody plants grow in height they alsogrow in thickness This added thick-ness called secondary growth resultsfrom cell divisions in the vascular cam-bium of the stem The xylem tissueproduced by secondary growth is alsocalled wood In temperate regions atreersquos annual growth rings are the lay-ers of vascular tissue produced eachyear by secondary growth Theseannual growth rings can be used toestimate the age of the plant The vas-cular tissues often contain scle-renchyma fibers that provide supportfor the growing plant
As secondary growth continues theouter portion of a woody stem devel-ops bark Bark is composed of phloemcells and the cork cambium Bark is atough corky tissue that protects thestem from damage by burrowinginsects and browsing herbivores
Stems transport materialsWater sugars and other com-
pounds are transported within thestem Xylem transports water and
616 PLANT STRUCTURE AND FUNCTIONCarolina BiologicalVisuals Unlimited
Figure 2315 Stems have vascularbundles
Cork
Phloem
Annual growth rings
Vascularcambium
Xylem
Woody stems are composedprimarily of dead xylem cells
C
The vascular bundlesin a monocot arescattered through-out the stem as seenin this cross section
A
As seen in this crosssection youngherbaceous dicotstems have separatebundles of xylem andphloem that form aring In older stemsthe vascular tissuesform a continuouscylinder
B
Color-enhanced LM Magnification 4
Color-enhanced LM Magnification 2
0612-0621 C23 S2 BDOL-829900 8404 1114 AM Page 616
dissolved minerals from the roots tothe leaves Water that is lost throughthe leaves is continually replaced bywater moving in the xylem Waterforms an unbroken column within thexylem As water moves up throughthe xylem it also carries dissolvedminerals to all living plant cells
The contents of phloem are pri-marily dissolved sugars but phloemalso can transport hormones virusesand other substances The sugarsoriginate in photosynthetic tissuesthat are usually in leaves Any portionof the plant that stores these sugars iscalled a sink such as the parenchymacells that make up the cortex in theroot The movement of sugars in thephloem is called translocation (transloh KAY shun) Figure 2316 showsthe movement of materials in the vas-cular tissues of a plant
Growth of the stemPrimary growth in a stem is similar
to primary growth in a root Thisincrease in length is due to the produc-tion of cells by the apical meristem
which lies at the tip of a stem As men-tioned earlier secondary growth or anincrease in diameter is the result of celldivisions in the vascular cambium orlateral meristem Meristems located atintervals along the stem called nodesgive rise to leaves and branches
LeavesThe primary function of the leaves
is photosynthesis Most leaves have arelatively large surface area thatreceives sunlight Sunlight passesthrough the transparent cuticle andepidermis into the photosynthetic tis-sues just beneath the leaf surface
Leaf variationWhen you think of a leaf you
probably think only of a flat broadgreen structure This part of the leafis called the leaf blade Sizes shapesand types of leaves vary enormouslyThe giant Victoria water lily thatgrows in some of the rivers of Guyanahas floating circular leaves that canbe more than two meters in diameter
232 ROOTS STEMS AND LEAVES 617
Water
Water lostthrough leaves
Xylem
Phloem
SugarSourceof sugars
Sieve plateCompanion cell
Sink
Figure 2316Xylem carries waterup from roots toleaves Phloem trans-ports sugars fromphotosynthetic tissuesto sinks locatedthroughout the plant
The open ends of xylem vessel cellsform complete pipelike tubes
A Sugars in the phloem of this carrot plant are moving to sinks
B
0612-0621 C23 S2 BDOL-829900 8404 1114 AM Page 617
The leaves of duckweed a commonfloating plant of ponds and lakes aremeasured in millimeters Some plantspecies commonly produce differentforms of leaves on one plant
Some leaves such as grass bladesare joined directly to the stem Inother leaves a stalk joins the leafblade to the stem This stalk which ispart of the leaf is called the petiole(PE tee ohl) The petiole contains vas-cular tissues that extend from thestem into the leaf and form veins Ifyou look closely you will notice theseveins as lines or ridges running alongthe leaf blade
Leaves vary in their shape andarrangement on the stem A simpleleaf is one with a blade that is notdivided When the blade is dividedinto leaflets it is called a compoundleaf Figure 2317 gives some exam-ples of the variety of leaf shapes
The arrangement of leaves on astem can vary Leaves can grow fromopposite sides of the stem in an alter-nating arrangement If two leavesgrow opposite each other on a stemthe arrangement is called oppositeThree or more leaves growing arounda stem at the same position is called awhorled arrangement
Leaf structureThe internal structure of a typical
leaf is shown in Figure 2318 Thevascular tissues are located in themidrib and veins of the leaf Justbeneath the epidermal layer are twolayers of mesophyll Mesophyll (MEH
zuh fihl) is the photosynthetic tissueof a leaf It is usually made up of twotypes of parenchyma cellsmdashpalisademesophyll and spongy mesophyllThe palisade mesophyll is made up ofcolumn-shaped cells containingmany chloroplasts These cells arefound just under the upper epidermis
618 PLANT STRUCTURE AND FUNCTION(l)Runk-SchoenbergerGrant Heilman Photography (c)Aaron Haupt (r)Runk-SchoenbergerGrant Heilman Photography
StomataGuard cell
PhloemXylem
Vascularbundle
Palisademesophyll
Cuticle
Spongy mesophyll
Lower epidermis
Upperepidermis
Figure 2318 The tissues of a leaf areadapted for photosynthe-sis gas exchange limitingwater loss and transport-ing water and sugars
Figure 2317Leaf shapes vary butmost are adapted toreceive sunlight
The needlelike leaves of theevergreen yew can receivesunlight year round
B
The tulip poplar is a deciduoustree with broad distinctivesimple leaves
C
The leaves of thewalnut are compoundwith many leaflets
A
0612-0621 C23 S2 BDOL-829900 8404 1115 AM Page 618
and receive maximum exposure tosunlight Most photosynthesis takesplace in the palisade mesophyllBelow the palisade mesophyll is thespongy mesophyll which is com-posed of loosely packed irregularlyshaped cells These cells usually aresurrounded by many air spaces thatallow carbon dioxide oxygen andwater vapor to freely flow around thecells Gases can also move in and outof a leaf through the stomata whichare located in the upper andor lowerepidermis
TranspirationYou read previously that leaves
have an epidermis with a waxy cuticleand stomata that help reduce waterloss Guard cells are cells that sur-round and control the size of a stomaas shown in Figure 2319 The loss ofwater through the stomata is calledtranspiration Learn more abouthow a plantrsquos surroundings may influ-ence rate of transpiration in Problem-Solving Lab 232 on this page
Stoma
Chloroplast
Epidermalcells
Guardcell
Thickenedwalls
Water
The guard cells have flexiblecell walls
A When water enters the guardcells the pressure causes themto bow out opening the stoma
B As water leaves the guard cells thepressure is released and the cellscome together closing the stoma
C
Figure 2319 Guard cells regulate the size of the open-ing of the stomata according to theamount of water in the plant
Draw ConclusionsWhat factors influence the rate of transpiration Plantslose large amounts of water during transpiration This processaids in pulling water up from roots to stem to leaves where itcan be used in photosynthesis
Solve the ProblemA student was interestedin seeing if a plantrsquos surroundings mightaffect its rate of waterloss A geranium plantwas set up as a control A second geranium wassealed within a plasticbag and a third gera-nium was placed infront of a fan All threeplants were placed under lights The studentrsquos experimental data are shown in the graph
Thinking Critically1 Infer Which line A B or C might best represent the stu-
dentrsquos control data Explain2 a Infer Which line might best represent the data with
the plant sealed within a bag Explainb Identify What abiotic environmental factor was being
tested 3 Infer Which line might best represent the data with the
plant in front of a fan Explain4 Conclude Write a conclusion for the studentrsquos experiment
Rate of Water Loss
Wat
er lo
ss
Time
A
B
C
0612-0621 C23 S2 BDOL-829900 8404 1115 AM Page 619
(bl)G
RR
ober
ts (
bc)D
rW
mM
Har
low
Pho
to R
esea
rche
rs (
br)A
lfred
Pas
ieka
Sci
ence
Pho
to L
ibra
ryP
hoto
Res
earc
hers
AA
BB
CC
The opening and closing of guardcells regulate transpiration As you readabout how guard cells work look againat the diagrams in Figure 2319 Guardcells are cells scattered among the cellsof the epidermis The walls of thesecells contain fiberlike structures Whenthere is more water available in sur-rounding cells than in guard cells waterenters guard cells by osmosis Thesefiberlike structures in the cell walls ofguard cells prevent expansion in widthnot in length Because the two guardcells are attached at either end thisexpansion in length forces them to bowout and the stoma opens When there isless water in surrounding tissues waterleaves the guard cells The cells returnto their previous shape which reducesthe size of the stoma The proper func-tioning of guard cells is importantbecause plants lose up to 90 percent ofall the water they transport from theroots by transpiration
Venation patternsOne way to distinguish among dif-
ferent groups of plants is to examine thepattern of veins in their leaves Theveins of vascular tissue run through themesophyll of the leaf As shown inFigure 2320 leaf venation patternsmay be parallel netlike or dichoto-mous You can learn more about leafvenation in the MiniLab shown here
Figure 2320Leaf venation patterns help distinguish between monocots and dicotsLeaves of corn plants have parallel veins (A) a characteristic of manymonocots Leaves of lettuce plants are netlike (B) a characteristic ofmany dicots Leaves of ginkgoes are dichotomously veined (C)
Compare and Contrast Observing Leaves Identifying leaf characteristics can helpyou identify plants Use these leaf images to complete thisfield investigation
ProcedureCAUTION Keep your hands away from your mouth whiledoing this investigation Wash your hands thoroughly afteryou complete your work With your teacherrsquos permission examine leaves on five dif-
ferent plants on your school campus or observe preservedleaves Do not use conifers
Sketch a leaf from each plant Beside each sketch labelthe leaf as simple or compound list its venation and writethe word that describes its arrangement on the stem
Analysis1 Collect and Organize Data As a class place leaves hav-
ing the same three characteristics into groups List thecharacteristics and count the number of leaves in eachgroup Display class results in a bar graph
2 Infer Why would a botanist compare and contrast leafstructure
Leaf type Leaf venation Leaf arrangement
Simple Palmate Opposite
CompoundPinnate Alternate
Parallel Whorled
0612-0621 C23 S2 BDOL-829900 8404 1116 AM Page 620
Leaf modificationsMany plants have leaves with struc-
tural adaptations for functions besidesphotosynthesis Some plant leaveshave epidermal growths as shown inFigure 2321A that release irritantswhen broken or crushed Animalsincluding humans learn to avoidplants with such leaves Cactus spinesare modified leaves that help reducewater loss from the plant and provideprotection from predators
Carnivorous plants like the pitcherplant in Figure 2321B have leaveswith adaptations that can trap insectsor other small animals Other leafmodifications include tendrils thecurly structures on sweet peas the
overlapping scales that enclose andprotect buds and the colorful bractsof poinsettias
Leaves often function as water orfood storage sites The leaves of Aloevera shown in Figure 2321C storewater This adaptation ensures thelong-term survival of the plant whenwater resources are scarce A bulbconsists of a shortened stem a flowerbud and thickened immature leavesFood is stored in the bases of theleaves Onions tulips narcissus andlilies all grow from bulbs
Evaluate the signifi-cance of leaf structural adaptationsto their environments
Understanding Main Ideas1 Compare and contrast the arrangement of xylem
and phloem in dicot roots and stems2 Infer where you would expect to find stomata in a
plant with leaves that float on water such as awater lily Explain
3 Describe the primary function of most leaves List some other functions of leaves
4 Explain how guard cells function and regulate thesize of a stoma
Thinking Critically5 Compare and contrast the function and structure
of the epidermis and the endodermis in a vascularplant
6 Get the Big Picture Construct a table that sum-marizes the structure and functions of roots stemsand leaves For more help refer to Get the BigPicture in the Skill Handbook
SKILL REVIEWSKILL REVIEW
232 ROOTS STEMS AND LEAVES 621
(l)A
ndre
w S
yred
Sci
ence
Pho
to L
ibra
ryP
hoto
Res
earc
hers
(c)
Imag
e re
prin
ted
from
The
Vis
ual D
ictio
nary
of
Pla
nts
with
per
mis
sion
fro
m D
orlin
g K
inde
rsle
y P
ublis
hing
(r)Alan amp Linda DetrickPhoto Researchers
Figure 2321Modified leaves servemany functions in addi-tion to photosynthesis
The surface of a tomato leaf hasglandular hairs that help repelinsects and other predators
A
The leaves of the pitcherplant are modified fortrapping insects
B
The leaves of Aloe vera are adapted tostore water in a dry desert environment
C
LM Magnification 350
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0612-0621 C23 S2 BDOL-829900 8404 1056 PM Page 621
233SECTION PREVIEWObjectivesIdentify the major typesof plant hormonesIdentify and analyze thedifferent types of plantresponses
Review Vocabularystimulus anything in an
organismrsquos internal orexternal environmentthat causes the organ-ism to react (p 9)
New Vocabularyhormoneauxingibberellincytokininethylenetropismnastic movement
Plant HormonesPlants like animals have hormones that regulate growth and develop-
ment A hormone is a chemical that is produced in one part of an organ-ism and transported to another part where it causes a physiological changeOnly a small amount of the hormone is needed to make this change
Auxins cause stem elongationThe group of plant hormones called
auxins (AWK sunz) promotes cell elongationIndoleacetic (in doh luh SEE tihk) acid(IAA)mdasha naturally occurring auxinmdashis pro-duced in apical meristems of plant stems IAAweakens the connections between the cellu-lose fibers in the cell wall which allows a cellto stretch and grow longer The combinationof new cells from the apical meristem andincreasing cell lengths leads to stem growthAuxin is not transported in the vascular sys-tem It moves from one parenchyma cell tothe next by active transport
Plant Responses
EnvisionPriscilla Connell
Shoot tip
Budsinhibited
Buds grow into side branches
Shoot tip removed
AA BB
622 PLANT STRUCTURE AND FUNCTION
Humans and Plants Respond to SunlightUsing an Analogy You step outside into the bright sunlight and immedi-ately raise your hand to shade your eyes You react quickly to the bright sunlight Plants react to sunlight too Often however plant responses to things in their environment are so slow that they can only be cap-tured by time-lapse photography When filmed in this way the flower heads of sunflowers can be seen mov-ing with the sunrsquos apparent movement across the sky In this section you will read about other plant stimuli and responsesMake and Use Tables As you read this section make a table of plant stimuli and responses Include the source of the stimulus and describe how the plant responds When studying this chapter use the table to review this section
Sunflowers
Figure 2322Auxin produced in the tip ofthe main shoot inhibits thegrowth of side branches (A)Once the tip is removed theside branches start to grow (B)
Objective 403 Assess describe and explain adaptations affecting survival and reproductive success Structural adaptations in plants and animals(form to function)
North Carolina Objectives
0622-0631 C23 S3 BDOL-829900 8404 1115 AM Page 622
BDOL-233
null
40544434
Auxins have other effects on plantgrowth and development Auxin pro-duced in the apical meristem inhibits thegrowth of side branches Removing thestem tip reduces the amount of auxinpresent and allows the development ofbranches as shown in Figure 2322
Auxin also delays fruit formation andinhibits the dropping of fruit from theplant When auxin concentrationsdecrease the ripened fruits of sometrees fall to the ground and deciduoustrees begin to shed their leaves
Infer how a fruitgrower might use auxins
Gibberellins promote growthThe group of plant growth hor-
mones called gibberellins (jih buhREH lunz) causes plants to grow tallerbecause like auxins they stimulate cellelongation Unlike auxins gibberellinsare transported in vascular tissueMany dwarf plants such as those inFigure 2323 are short because theplant does not produce gibberellins orits cells are not receptive to the hor-mone If gibberellins are applied to thetip of a dwarf plant it will grow tallerGibberellins also increase the rate ofseed germination and bud develop-ment Farmers have learned to use gib-berellins to enhance fruit formationFlorists often use gibberellins toinduce flower buds to open
Cytokinins stimulate cell division
The hormones called cytokinins(si tuh KI nihnz) stimulate mitosis andcell division Cytokinins stimulate theproduction of proteins needed formitosis and cell division Most cyto-kinins are produced in root meristemsThis hormone travels up the xylem toother parts of the plant The effects ofcytokinins are often enhanced by thepresence of other hormones
Ethylene gas promotes ripeningThe plant hormone ethylene (EH
thuh leen) is a simple gaseous com-pound composed of carbon andhydrogen It is produced primarily byfruits but also by leaves and stemsEthylene is released during a specificstage of fruit ripening It causes cellwalls to weaken and become softEthylene speeds the ripening of fruitsand promotes the breakdown of com-plex carbohydrates to simple sugarsIf you have ever enjoyed a ripe redapple you know that it tastes sweeterthan an immature fruit
Many farmers use ethylene toripen green fruits or vegetables afterthey have been picked as shown inFigure 2324
233 PLANT RESPONSES 623
auxin from theGreek word auxeinmeaning ldquotoincreaserdquo Auxincauses stem elon-gation by increasingcell length
(t)R
unk-
Sch
oenb
erge
rG
rant
Hei
lman
Pho
togr
aphy
(bl)EnvisionOsentoski amp Zoda (br)A Louis GoldmanPhoto Researchers
Figure 2323 The bean plants in thispicture are geneticdwarfs The two plantson the right weretreated with gibberellinand have grown to anormal height
Figure 2324 Tomatoes are usually pickedwhen they are green then theyare treated with ethyleneMost of the tomatoes you seein grocery stores have beenripened in this manner
0622-0631 C23 S3 BDOL-829900 8404 1117 AM Page 623
Lightsource
Elongated cells
Plant ResponsesWhy do roots grow down and most
stems grow up Although a plantlacks a nervous system and usuallycannot make quick responses to stim-uli it does have mechanisms thatenable it to respond to its environ-ment Plants grow reproduce andreposition their roots stems andleaves in response to environmentalconditions such as gravity light tem-perature and amount of darkness
Tropic responses in plantsAt the beginning of this section
you read that the flower heads of sun-flowers slowly respond to the sunrsquosapparent movement across the skyTropism is a plantrsquos response to anexternal stimulus The tropism iscalled positive if the plant growstoward the stimulus The tropism iscalled negative if the plant growsaway from the stimulus
The growth of a plant toward light iscalled phototropism It is caused by anunequal distribution of auxin in theplantrsquos stem There is more auxin onthe side of the stem away from thelight This results in cell elongationbut only on that side As these cellslengthen the stem bends toward thelight as shown in Figure 2325A Youcan learn more about phototropism inthe Problem-Solving Lab on this page
There is another tropism associatedwith the upward growth of stems andthe downward growth of roots Gravi-tropism is plant growth in response togravity Gravitropic responses are ben-eficial to plants Roots that grow downinto the soil are able to anchor theplant and can take in water and dis-solved minerals Stems usually exhibit anegative gravitropism
Some plants exhibit another tropismcalled thigmotropism which is agrowth response to touch The tendrils
Jim W GracePhoto Researchers
Figure 2325Phototropism is the growthresponse of a plant towardlight (A) Thigmotropism isa growth response totouch (B)
624
AA
BB
Draw a ConclusionHow do plant stems respond to light While working with young oat plants Charles Darwin made discoveries about the response of young plant stems to light that helped explainwhy plants undergo phototropism Scientists now know that this response is the result of an auxin that causes rapid cell elongation to occur along one side of a young plant stem However auxins were unknown during Darwinrsquos time
Solve the ProblemStudy the before and after diagrams The three plants areyoung oat stems Note that the light source is directed at theplants from one side
Thinking Critically1 Interpret Scientific Illustrations Which diagram (or
diagrams) supports the conclusion that light is the stimulusfor phototropism Explain
2 Interpret Scientific Illustrations Which diagram (or diagrams) supports the conclusion that the stem tip is thestimulus for phototropism Explain
3 Conclude Where might the auxin responsible for phototropism be produced Explain
BeforeA B C A B C
After
Opaquecover
0622-0631 C23 S3 BDOL-829900 8404 1118 AM Page 624
Understanding Main Ideas1 Define a hormone
2 Compare and contrast tropic responses and nasticmovements
3 Explain how a plant can bend toward sunlightWhat term describes this response
4 Name one plant hormone and describe how itfunctions
5 Explain why gardeners often remove stem tips ofchrysanthemum plants during early summer
Thinking Critically6 One technique that has been used for years to
ripen fruit is to put a ripened banana in a paperbag with the unripe fruit Infer what happensinside the bag
7 Experiment Explain how you would design anexperiment to investigate the effects of differentcolors of light on the phototropism of a plant For more help refer to Experiment in the SkillHandbook
SKILL REVIEWSKILL REVIEW
233 PLANT RESPONSES 625(tl)Christi CarterGrant Heilman Photography (bl)Christi CarterGrant Heilman Photography (tr)Runk-SchoenbergerGrant Heilman Photography
of the vine in Figure 2325B havecoiled around a fence after makingcontact during early growth
Because tropisms involve growththey are not reversible The positionof a stem that has grown severalinches in a particular direction cannotbe changed But if the direction ofthe stimulus is changed the stem willbegin growing in another direction
Nastic responses in plantsA responsive movement of a plant
that is not dependent on the directionof the stimulus is called a nasticmovement An example of a nasticmovement is the movement ofMimosa pudica leaflets when they are
touched as shown in Figure 2326AThis is caused by a change in waterpressure in the cells at the base ofeach leaflet A dramatic drop in pres-sure causes the cells to become limpand the leaflets to change orientation
Another example of a nasticresponse is the sudden closing of thehinged leaf of a Venusrsquos-flytrap Figure 2326B If an insect triggerssensitive hairs on the inside of theleaf the leaf snaps shut Nasticresponses that are due to changes incellular water pressure are reversiblebecause they do not involve growthThe Mimosa pudica and Venusrsquos-flytrap leaves return to their originalpositions once the stimulus ends
AA BB
Figure 2326When leaflets ofMimosa pudica aretouched they moveinward (A) Trigger hairsmust be touched toclose the hinged leaf ofa Venusrsquos-flytrap (B)Infer How do theseadaptations helpensure the long-termsurvival of eachspecies
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0622-0631 C23 S3 BDOL-829900 8404 1102 PM Page 625
626 PLANT STRUCTURE AND FUNCTION
Before YouBegin
If asked to count the totalnumber of stomata on aleaf you might answer bysaying ldquothatrsquos an impossi-ble taskrdquo It may not benecessary for you to counteach and every stomaSampling is a techniquethat is used to arrive at ananswer that is close to theactual number You willuse a sampling techniquein this BioLab
1
2
3
4
5
Total
Average
Number of StomataTrial
Data Table 1
Determining the Number of Stomata on a Leaf
Problem How can you count the total number of stomata on a leaf
Objectives In this BioLab you will Measure the area of a leaf Observe the number of stomata seen under a high-power
field of view Calculate the total number of stomata on a leaf Use the Internet to collect and compare data from other
students
Materials microscope rulerglass slide coverslipwater and dropper green leaf from an onion single-edged razor blade plant
Safety PrecautionsCAUTION Wear latex gloves when handling an onion
Skill HandbookIf you need help with this lab refer to the Skill Handbook
1 Copy Data Table 1 and Data Table 22 To calculate the area of the high-power field of view
for your microscope go to Math Skills in the SkillHandbook Enter the area in Data Table 2
3 Obtain an onion leaf and carefully cut it open lengthwiseusing a single-edged razor blade CAUTION Be carefulwhen cutting with a razor blade
4 Measure the length and width of your onion leaf inmillimeters Record these values in Data Table 2
5 Remove a small section of leaf and place it on a glassslide with the dark green side facing DOWN
6 Add several drops of water and gently scrape away all greenleaf tissue using the razor blade An almost transparentlayer of leaf epidermis will be left on the slide
PROCEDUREPROCEDURE
PREPARATIONPREPARATION
0622-0631 C23 S3 BDOL-829900 8404 1120 AM Page 626
LM Magnification 200
7 Add water and a coverslip to the epidermis Observe under low-power magnification and locate an area where guard cells and stomata can be seen clearly CAUTION Use caution when handling a microscope microscope slides and coverslips
8 Switch to high-power magnification9 Count the number of stomata in your field of view
This is Trial 1 Record your count in Data Table 110 Move the slide to a different area Count the number
of stomata in this field of view This is Trial 2 Record your count in Data Table 1
11 Repeat step 10 for Trials 3 4 and 5 Calculate the average number of stomata observed
12 Calculate the total number of stomataon the entire onion leaf by followingthe directions in Data Table 2
13 Clean allequipment as instructed by yourteacher and return everything to itsproper place Dispose of leaf tissueand coverslips properly Wash yourhands thoroughly
CLEANUP AND DISPOSAL
Area of high-power field of view
Length of leaf portion in mm
Width of leaf portion in mm
Calculate area of leaf (length width)
Calculate number of high-power fields of view on leaf (area of leaf the area of one high-power field of view)
Calculate total number of stomata (numberof high-power fields of view average number of stomata from Data Table 1)
_____ mm2
_____ mm
_____ mm2
_____
_____
Data Table 2
_____ mm
ANALYZE AND CONCLUDEANALYZE AND CONCLUDE
1 Communicate Compare your data with those of your classmates Offerseveral reasons why your total number of stomata for the leaf may not beidentical to your classmates
2 Predict Would you expect all plants to have the same number of stomataper high-power field of view Explain your answer
3 Compare and Contrast What are theadvantages to using sampling techniquesWhat are some limitations
4 Analyze the following pro-cedures from this experiment and explainhow you can change them to improve theaccuracy of your dataa five trials in Data Table 1b calculating the area of your high-power
field of view
ERROR ANALYSISInterpret Data Find this BioLab using thelink below and post your data in the datatables provided for this activity Using theadditional data from other students on theInternet analyze the combined data andcomplete your graph
233 PLANT RESPONSES 627Andrew SyredScience Photo LibraryPhoto Researchers
ncbdolglencoecominternet_lab
0622-0631 C23 S3 BDOL-829900 8404 1103 PM Page 627
628 PLANT STRUCTURE AND FUNCTION
Red Poppyby Georgia OrsquoKeeffe (1887ndash1986)
ldquoWhen you take a flower in your hand andreally look at itrdquo OrsquoKeeffe said cupping herhand and holding it close to her face ldquoitrsquosyour world for the moment I want to givethat world to someone else Most people inthe city rush around so they have no time tolook at a flower I want them to see itwhether they want to or notrdquo
American artist GeorgiaOrsquoKeeffe attracted
much attention when thefirst of her many floralscenes was exhibited inNew York in 1924Everything about thesepaintingsmdashtheir colorsize point of view andstylemdashoverwhelmed theviewerrsquos senses just as theircreator had intended
In describing her huge paintingsof solitary flowers Georgia OrsquoKeeffe said ldquoI decided that I wasnrsquot going to spend my lifedoing what had already been donerdquo Indeed shedid do what had not been done by paintingenormous poppies lilies and irises on giant can-vases Her use of colors and emphasis on shapessuggests nature rather than copying it with pho-tographic realism Her work can be described asabstract ldquoI found that I could say things withcolor and shapes that I couldnrsquot say in any otherwaymdashthings that I had no words forrdquo she said
The viewerrsquos eye is drawn into theflowerrsquos heart In this early representation ofone of her familiar poppies OrsquoKeeffe directedthe viewerrsquos eye down into the poppyrsquos center bycontrasting the light tints of the outer ring ofpetals with the darkness of the poppyrsquos center
The viewerrsquos eye is drawn to the center of theflower much as the flower naturally attracts aninsect for reproduction purposes The over-whelming size and detailed interiors ofOrsquoKeeffersquos flowers give an effect similar to aphotographerrsquos close-up camera angle
During her long life OrsquoKeeffe created hun-dreds of paintings Her subjects included the flow-ers for which she is perhaps most famous as wellas other botanical themes Her paintings of NewMexico deserts are characterized by sweepingforms that portray sunsets rocks and cliffs
Georgia OrsquoKeeffe died in New Mexico in1986 She is remembered for her bold vividpaintings that are indeed larger than life
(l)Paul StrandNational Portrait Gallery Smithsonian InstitutionArt Resource NY (r)Art Resource NYThe Georgia OrsquoKeeffe FoundationArtists Rights Society New York
Critique Itrsquos easy to identify the flowers inOrsquoKeeffersquos paintings but can they be consideredscientific models Look at the poppy flower photo-graph on page 957 of this book Write a critiquethat evaluates each of these modelsmdashOrsquoKeeffersquospoppy and the photographmdashaccording to its ade-quacy in representing a poppy flower
To find out more about Georgia OrsquoKeeffevisit ncbdolglencoecomart
0622-0631 C23 S3 BDOL-829900 8404 1105 PM Page 628
Section 231
Section 232
Key Concepts Most plant tissues are composed of
parenchyma cells collenchyma cells and sclerenchyma cells
Dermal tissue is a plantrsquos protective covering Xylem moves water and dissolved minerals
up from roots and throughout the plantPhloem transports sugars and organiccompounds throughout the plant
Ground tissue often functions in food production and storage
Meristematic tissues undergo cell divisionsMost plant growth results from new cellsproduced in the meristems
Vocabularyapical meristem (p 611)collenchyma (p 606)companion cell (p 610)cork cambium (p 611)epidermis (p 607)guard cell (p 607)meristem (p 611)parenchyma (p 605)phloem (p 610)sclerenchyma (p 606)sieve tube member
(p 610)stomata (p 607)tracheid (p 608)trichome (p 607)vascular cambium
(p 611)vessel element (p 608)xylem (p 608)
Plant Cells andTissues
Vocabularycortex (p 613)endodermis (p 613)mesophyll (p 618)pericycle (p 614)petiole (p 618)root cap (p 615)sink (p 617)translocation (p 617)transpiration (p 619)
CHAPTER 23 ASSESSMENT 629(t)Microfiled Scientific LTDScience Photo LibraryPhoto Researchers (c)Runk-SchoenbergerGrant Heilman Photography (b)Runk-SchoenbergerGrant Heilman Photography
To help you reviewplant structure and function use theOrganizational Study Fold on page 605
STUDY GUIDESTUDY GUIDE
Vocabularyauxin (p 622)cytokinin (p 623)ethylene (p 623)gibberellin (p 623)hormone (p 622)nastic movement
(p 625)tropism (p 624)
PlantResponses
Section 233
Roots Stemsand Leaves
Color-enhanced SEM Magnification 200
Key Concepts Roots anchor plants and contain vascular
tissues Root hairs absorb water oxygenand dissolved minerals A root cap coversand protects each root tip
Stems provide support contain vasculartissues and produce leaves Some stemsare underground
Leaves undergo photosynthesis A stoma is an opening in the leaf epidermis is sur-rounded by two guard cells and takes inand releases gases Veins in leaves are bundles of vascular tissues
Key Concepts Plant hormones affect plant growth and
functions Tropisms are growth responses to external
stimuli Some nastic responses are caused by
changes in cell pressure
ncbdolglencoecomvocabulary_puzzlemaker
0622-0631 C23 S3 BDOL-829900 8404 1106 PM Page 629
630 CHAPTER 23 ASSESSMENT
Review the Chapter 23 vocabulary words listed inthe Study Guide on page 629 For each set ofvocabulary words choose the one that does notbelong Explain why it does not belong
1 parenchymamdashsclerenchymamdashapical meristem2 vessel elementmdashsieve tube membermdash
companion cell3 stomatamdashvascular cambiummdashepidermis4 root capmdashtranslocationmdashsink5 cytokininmdashhormonemdashtropism
6 The tissue that makes up the protective covering of a plant is ________ tissueA vascular C groundB meristematic D dermal
7 This root cross sectionwith a core of vasculartissue is typical of________ plantsA horsetailB monocotC dicotD moss
8 A cambium and a meristem are examples of________ tissuesA support C growthB protective D transport
9 One of the primary structural differencesbetween dicot roots and stems is the________A arrangement of vascular tissues in roots
and stemsB presence of stomata in roots C lack of an epidermis in stemsD presence of an apical meristem in stems
only10 The ripening of fruit is stimulated by the
presence of ________A gibberellinB ethyleneC auxinD cytokinin
11 Which diagram correctly shows the func-tioning of guard cells
A
B
12 Which terms complete this concept mapA tracheids and
vessel elementsB companion cells
and fibersC tracheids and
sieve tubesD companion cells
and sieve tubes
13 Open Ended In late winter some sugarmaple trees have holes drilled in their trunksin order to collect their sap a sugary fluidThis sap is processed to make maple syrupExplain the source of the sap and identify theplant system and subsystem that contains it
14 Open Ended How does the endodermiscontrol the flow of water and ions into rootvascular tissues
15 Compare and Contrast Identify and ana-lyze characteristics of plant systems and subsystems
16 More than5000 products are made from the vasculartissues of about 1000 tree species in theUnited States Investigate the production oflumber paper fuel charcoal and its prod-ucts fabrics maple syrup spices dyes anddrugs that come from vascular tissues Visit
to research these topics Prepare and present a poster or multimedia presentation of your findings
REAL WORLD BIOCHALLENGE
Water
Water
Water istransported in
is composed of
6xylem
ncbdolglencoecom
ncbdolglencoecomchapter_test
0622-0631 C23 S3 BDOL-829900 8404 1107 PM Page 630
Multiple ChoiceUse data in the graph below to answer questions17 and 18
17 Copper is an important soil micronutrientfor plants According to the graph the cop-per concentration that resulted in the wood-iest stem is ________A 3 ppmB 05 ppmC 15 ppmD 4 ppm
18 Without enough copper branches of someconifers twist as they grow If you were atree grower and some of your conifer treesrsquobranches were twisted and bent what is thecorrect course of action to take firstA Water the trees moreB Apply fertilizerC Test the soil to determine
nutrient levelsD Apply a pesticide
Leaf samples from the same plant species werecollected from four different locations Stomatawere counted and averaged and the data weregraphed as shown below Use the graph toanswer questions 19 and 20
19 In which location might there be the mostrainfallA State AB State BC State CD State D
20 How might the number of stomata correlatewith the amount of rainfallA more stomata less rainfallB no stomata no rainfallC more stomata more rainfallD fewer stomata more rainfall
Nu
mb
er o
f st
om
ata
leaf
Origin of leavesState A State B State C State D
Comparison of Numbers of Stomata
Rat
ing
Copper concentrationparts per million (ppm)
0
0 1 2 3 4
1
2
3
4
Stem Woodiness
Constructed ResponseGrid InRecord your answers on your answer document
21 Open Ended Sometimes foresters kill selected trees to reduce competition for limited environ-mental resources They often use a process called girdling that involves removing a band of barkand some wood from around the trunk of a tree Once this circle of material is removed the treeeventually dies Explain why this can happen
22 Open Ended In the last decade over three million acres of privately owned forested land hasbeen converted to agricultural uses real estate development and other uses Describe whatmight be the biological and ecological results of these changes
CHAPTER 23 ASSESSMENT 631ncbdolglencoecomstandardized_test
The assessed North Carolina objective appears next to the question
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0622-0631 C23 S3 BDOL-829900 8404 1108 PM Page 631
- Biology The Dynamics of LifemdashNorth Carolina Edition
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- Contents in Brief
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- The North Carolina Biology Handbook
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- Correlations to the North Carolina Objectives
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- North Carolina Objectives to Biology The Dynamics of Life
- Biology The Dynamics of Life to North Carolina Objectives
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- How to Master the North Carolina Objectives
- End-of-Course Test Practice Countdown
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- Table of Contents
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- Unit 1 What is biology
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- Chapter 1 Biology The Study of Life
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- Section 11 What is biology
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- MiniLab 11 Predicting Whether Mildew Is Alive
- Careers in Biology Nature Preserve Interpreter
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- Section 12 The Methods of Biology
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- MiniLab 12 Testing for Alcohol
- Problem-Solving Lab 11
- Inside Story Scientific Methods
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- Section 13 The Nature of Biology
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- Problem-Solving Lab 12
- MiniLab 13 Hatching Dinosaurs
- Internet BioLab Collecting Biological Data
- Biology and Society Organic Food Is it healthier
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- Chapter 1 Assessment
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- BioDigest What is biology
- Unit 1 Standardized Test Practice
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- Unit 2 Ecology
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- Chapter 2 Principles of Ecology
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- Section 21 Organisms and Their Environment
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- MiniLab 21 Salt Tolerance of Seeds
- Problem-Solving Lab 21
- Careers in Biology Science Reporter
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- Section 22 Nutrition and Energy Flow
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- Problem-Solving Lab 22
- Physical Science Connection Conservation of Energy
- Physical Science Connection Conservation of Mass
- MiniLab 22 Detecting Carbon Dioxide
- Inside Story The Carbon Cycle
- Design Your Own BioLab How can one population affect another
- Biology and Society The EvergladesmdashRestoring an Ecosystem
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- Chapter 2 Assessment
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- Chapter 3 Communities and Biomes
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- Section 31 Communities
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- MiniLab 31 Looking at Lichens
- Problem-Solving Lab 31
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- Section 32 Biomes
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- Physical Science Connection Salinity and Density of a Solution
- Problem-Solving Lab 32
- MiniLab 32 Marine Plankton
- Inside Story A Tropical Rain Forest
- Investigate BioLab Succession in a Jar
- Connection to Literature Our National Parks by John Muir
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- Chapter 3 Assessment
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- Chapter 4 Population Biology
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- Section 41 Population Dynamics
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- MiniLab 41 Fruit Fly Population Growth
- Inside Story Population Growth
- Problem-Solving Lab 41
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- Section 42 Human Population
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- Problem-Solving Lab 42
- MiniLab 42 Doubling Time
- Investigate BioLab How can you determine the size of an animal population
- Connection to Chemistry Polymers for People
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- Chapter 4 Assessment
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- Chapter 5 Biological Diversity and Conservation
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- Section 51 Vanishing Species
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- MiniLab 51 Field Investigation
- Problem-Solving Lab 51
- Physical Science Connection Environmental Impact of Generating Electricity
- Physical Science Connection Wave Energy
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- Section 52 Conservation of Biodiversity
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- MiniLab 52 Conservation of Soil
- Problem-Solving Lab 52
- Internet BioLab Researching Information on Exotic Pets
- Connection to Art Photographing Life
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- Chapter 5 Assessment
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- BioDigest Ecology
- Unit 2 Standardized Test Practice
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- Unit 3 The Life of a Cell
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- Chapter 6 The Chemistry of Life
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- Section 61 Atoms and Their Interactions
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- Problem-Solving Lab 61
- Physical Science Connection Chemical Bonding and the Periodic Table
- Physical Science Connection Conservation of Mass in Chemical Reactions
- Careers in Biology WeedPest Control Technician
- MiniLab 61 Determine pH
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- Section 62 Water and Diffusion
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- Physical Science Connection The Structure of Water Molecules
- Physical Science Connection Density of Liquids
- Problem-Solving Lab 62
- MiniLab 62 Investigate the Rate of Diffusion
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- Section 63 Life Substances
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- Inside Story Action of Enzymes
- Design Your Own BioLab Does temperature affect an enzyme reaction
- BioTechnology The Good News and the Bad News About Cholesterol
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- Chapter 6 Assessment
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- Chapter 7 A View of the Cell
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- Section 71 The Discovery of Cells
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- Physical Science Connection Lenses and the Refraction of Light
- MiniLab 71 Measuring Objects Under a Microscope
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- Section 72 The Plasma Membrane
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- Problem-Solving Lab 71
- Physical Science Connection Solubility and the Nature of Solute and Solvent
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- Section 73 Eukaryotic Cell Structure
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- Problem-Solving Lab 72
- MiniLab 72 Cell Organelles
- Physical Science Connection Conservation of Energy
- Inside Story Comparing Animal and Plant Cells
- Investigate BioLab Observing and Comparing Different Cell Types
- Connection to Literature The Lives of a Cell by Lewis Thomas
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- Chapter 7 Assessment
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- Chapter 8 Cellular Transport and the Cell Cycle
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- Section 81 Cellular Transport
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- MiniLab 81 Cell Membrane Simulation
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- Section 82 Cell Growth and Reproduction
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- Problem-Solving Lab 81
- Problem-Solving Lab 82
- Inside Story Chromosome Structure
- MiniLab 82 Seeing Asters
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- Section 83 Control of the Cell Cycle
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- Problem-Solving Lab 83
- Investigate BioLab Where is mitosis most common
- Connection to Health Skin Cancer
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- Chapter 8 Assessment
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- Chapter 9 Energy in a Cell
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- Section 91 The Need for Energy
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- Problem-Solving Lab 91
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- Section 92 Photosynthesis Trapping the Suns Energy
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- MiniLab 91 Separating Pigments
- MiniLab 92 Use Isotopes to Understand Photosynthesis
- Inside Story The Calvin Cycle
- Biotechnology Careers Biochemist
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- Section 93 Getting Energy to Make ATP
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- Inside Story The Citric Acid Cycle
- Problem-Solving Lab 92
- MiniLab 93 Determine if Apple Juice Ferments
- Internet BioLab What factors influence photosynthesis
- Connection to Chemistry Plant Pigments
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- Chapter 9 Assessment
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- BioDigest The Life of a Cell
- Unit 3 Standardized Test Practice
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- Unit 4 Genetics
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- Chapter 10 Mendel and Meiosis
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- Section 101 Mendels Laws of Heredity
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- MiniLab 101 Looking at Pollen
- Problem-Solving Lab 101
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- Section 102 Meiosis
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- Problem-Solving Lab 102
- MiniLab 102 Modeling Crossing Over
- Inside Story Chromosome Mapping
- Internet BioLab How can phenotypes and genotypes of plants be determined
- Connection to Math A Solution from Ratios
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- Chapter 10 Assessment
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- Chapter 11 DNA and Genes
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- Section 111 DNA The Molecule of Heredity
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- Problem-Solving Lab 111
- Inside Story Copying DNA
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- Section 112 From DNA to Protein
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- Problem-Solving Lab 112
- MiniLab 111 Transcribe and Translate
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- Section 113 Genetic Changes
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- Physical Science Connection Gamma Radiation as a Wave
- Careers in Biology Genetic Counselor
- Problem-Solving Lab 113
- MiniLab 112 Gene Mutations and Proteins
- Investigate BioLab RNA Transcription
- BioTechnology Scanning Probe Microscopes
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- Chapter 11 Assessment
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- Chapter 12 Patterns of Heredity and Human Genetics
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- Section 121 Mendelian Inheritance of Human Traits
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- MiniLab 121 Illustrating a Pedigree
- Problem-Solving Lab 121
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- Section 122 When Heredity Follows Different Rules
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- Problem-Solving Lab 122
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- Section 123 Complex Inheritance of Human Traits
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- Inside Story The ABO Blood Group
- Problem-Solving Lab 123
- MiniLab 122 Detecting Colors and Patterns in Eyes
- Design Your Own BioLab What is the pattern of cytoplasmic inheritance
- Connection to Social Studies Queen Victoria and Royal Hemophilia
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- Chapter 12 Assessment
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- Chapter 13 Genetic Technology
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- Section 131 Applied Genetics
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- Problem-Solving Lab 131
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- Section 132 Recombinant DNA Technology
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- MiniLab 131 Matching Restriction Enzymes to Cleavage Sites
- Inside Story Gel Electrophoresis
- Problem-Solving Lab 132
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- Section 133 The Human Genome
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- MiniLab 132 Storing the Human Genome
- Biotechnology Careers Forensic Analyst
- Problem-Solving Lab 133
- Investigate BioLab Modeling Recombinant DNA
- BioTechnology New Vaccines
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