chapter 35

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint TextEdit Art Slides forBiology, Seventh Edition

Neil Campbell and Jane Reece

Chapter 35Chapter 35

Plant Structure, Growth, and Development


Figure 35.1 Fanwort (Cabomba caroliniana)


Figure 35.2 An overview of a flowering plant

Reproductive shoot (flower)

Terminal bud

NodeInternode

Terminalbud

Vegetativeshoot

BladePetiole

Stem

Leaf

Taproot

Lateral roots Rootsystem

Shootsystem

Axillarybud


Figure 35.3 Root hairs and root tip


Figure 35.4 Modified roots

(a) Prop roots (b) Storage roots (c) “Strangling” aerialroots

(d) Buttress roots (e) Pneumatophores


Figure 35.5 Modified stems

Rhizomes. The edible base of this ginger plant is an example of a rhizome, a horizontal stem that grows just below the surface or emerges and grows along thesurface.

(d)

Tubers. Tubers, such as these red potatoes, are enlarged ends of rhizomes specializedfor storing food. The “eyes” arranged in a spiral pattern around a potato are clusters of axillary buds that markthe nodes.

(c)

Bulbs. Bulbs are vertical,underground shoots consistingmostly of the enlarged bases of leaves that store food. You can see the many layers of modified leaves attached to the short stem by slicing an onion bulb lengthwise.

(b)

Stolons. Shown here on a strawberry plant, stolons are horizontal stems that grow along the surface. These “runners”enable a plant to reproduce asexually, as plantlets form at nodes along each runner.

(a)

Storage leaves

Stem

Root Node

Rhizome

Root


Figure 35.6 Simple versus compound leaves

Petiole

(a) Simple leaf. A simple leafis a single, undivided blade.Some simple leaves are deeply lobed, as in anoak leaf.

(b) Compound leaf. In acompound leaf, theblade consists of multiple leaflets.Notice that a leaflethas no axillary budat its base.

(c) Doubly compound leaf. In a doubly compound leaf, each leaflet is divided into smaller leaflets.

Axillary bud

Leaflet

Petiole

Axillary bud

Axillary bud

LeafletPetiole


Figure 35.7 Modified leaves(a) Tendrils. The tendrils by which this

pea plant clings to a support are modified leaves. After it has “lassoed” a support, a tendril forms a coil that brings the plant closer to the support. Tendrils are typically modified leaves, but some tendrils are modified stems, as in grapevines.

(b) Spines. The spines of cacti, such as this prickly pear, are actually leaves, and photosynthesis is carried out mainly by the fleshy green stems.

(c) Storage leaves. Most succulents, such as this ice plant, have leaves modified for storing water.

(d) Bracts. Red parts of the poinsettia are often mistaken for petals but are actually modified leaves called bracts that surround a group of flowers. Such brightly colored leaves attract pollinators.

(e) Reproductive leaves. The leaves of some succulents, such as Kalanchoe daigremontiana, produce adventitious plantlets, which fall off the leaf and take root in the soil.


Figure 35.8 The three tissue systems

Dermaltissue

Groundtissue Vascular

tissue


Figure 35.9 Examples of Differentiated Plant CellsPARENCHYMA CELLS

COLLENCHYMA CELLS

SCLERENCHYMA CELLS

SUGAR-CONDUCTING CELLS OF THE PHLOEM

WATER-CONDUCTING CELLS OF THE XYLEM

Parenchyma cells 60 m

80 m

5 m

25 m

Cell wall

Sclereid cells in pear

Fiber cells

Cortical parenchyma cells

Collenchyma cells

Vessel Tracheids 100 m

Tracheids and vessels

Vesselelement

Vessel elements withpartially perforated end walls

Pits

Sieve-tube members:longitudinal view

Companioncell

Sieve-tubemember

Sieveplate

Nucleus

Cytoplasm Companioncell

30 m

15 m

Tracheids


Figure 35.10 An overview of primary and secondary growth

In woody plants, there are lateral meristems that add secondary

growth, increasing the girth of

roots and stems.

Apical meristems add primary growth,

or growth in length.

Vascularcambium

Corkcambium

Lateralmeristems

Root apicalmeristems

Primary growth in stems

Epidermis

Cortex

Primary phloem

Primary xylem

Pith

Secondary growth in stems

PeridermCorkcambium

CortexPrimary phloem

Secondaryphloem

Vascular cambium

Secondaryxylem

Primaryxylem

Pith

Shoot apicalmeristems(in buds)

The Corkcambium addssecondarydermal tissue.

The vascularcambium addssecondaryxylem andphloem.


Figure 35.11 Three years’ past growth evident in a winter twig

This year’s growth(one year old)

Last year’s growth(two years old)

Growth of twoyears ago (threeyears old)

One-year-old sidebranch formedfrom axillary budnear shoot apex

Scars left by terminalbud scales of previouswinters

Leaf scar

Leaf scar

Stem

Leaf scar

Bud scale

Axillary buds

Internode

Node

Terminal bud


Figure 35.12 Primary growth of a root

Dermal

Ground

Vascular

Key

Cortex Vascular cylinder

Epidermis

Root hair

Zone ofmaturation

Zone ofelongation

Zone of celldivision

Apicalmeristem

Root cap

100 m


13.12 Time Lapse Root


Figure 35.13 Organization of primary tissues in young roots

Cortex

Vascularcylinder

Endodermis

Pericycle

Core ofParenchymacells

Xylem

50 m

Endodermis

Pericycle

Xylem

Phloem

Key

100 m

Vascular

GroundDermal

Phloem

Transverse section of a root with parenchymain the center. The stele of many monocot roots is a vascular cylinder with a core of parenchymasurrounded by a ring of alternating xylem and phloem.

(b)Transverse section of a typical root. In theroots of typical gymnosperms and eudicots, aswell as some monocots, the stele is a vascularcylinder consisting of a lobed core of xylemwith phloem between the lobes.

(a)

100 m

Epidermis


Figure 35.14 The formation of a lateral root

Cortex

Vascularcylinder

Epidermis

Lateral root

100 m

1 2

3 4

Emerginglateralroot


Figure 35.15 The terminal bud and primary growth of a shoot

Apical meristem Leaf primordia

Developingvascularstrand

Axillary budmeristems

0.25 mm


Figure 35.16 Organization of primary tissues in young stems

EpidermisVascularbundle

Cortex

Pith

Ground tissueconnecting pith to cortex

XylemPhloem

Sclerenchyma(fiber cells)

Groundtissue

Epidermis

Vascularbundles

Key

Dermal

GroundVascular

1 mm 1 mm

(a) A eudicot stem. A eudicot stem (sunflower), withvascular bundles forming a ring. Ground tissue towardthe inside is called pith, and ground tissue toward theoutside is called cortex. (LM of transverse section)

(b) A monocot stem. A monocot stem (maize) with vascularbundles scattered throughout the ground tissue. In such anarrangement, ground tissue is not partitioned into pith andcortex. (LM of transverse section)


Figure 35.17 Leaf anatomyKey

to labels

DermalGround

Vascular

Guardcells

Stomatal pore

Epidermalcell

50 µm

Surface view of a spiderwort(Tradescantia) leaf (LM)

(b)Cuticle

Sclerenchymafibers

Stoma

Upperepidermis

Palisademesophyll

Spongymesophyll

Lowerepidermis

Cuticle

Vein

Guard cells

Xylem

Phloem

Guard cells

Bundle-sheathcell

Cutaway drawing of leaf tissues(a)

Vein Air spaces Guard cells

100 µmTransverse section of a lilac(Syringa) leaf (LM)

(c)


Figure 35.18 Primary and secondary growth of a stem (layer 1)

(a) Primary and secondary growth in a two-year-old stem

Pith

Primary xylemVascular cambium

Primary phloem

Epidermis

Cortex

1



Vascular cambium

4 First cork cambium

Pith


Primary phloem

Epidermis

Cortex

2

1

Growth

Primary xylem

Secondary xylemPrimary phloem

Cork

Phloem ray3 Xylem

ray

Secondary phloem




Vascular cambiumPith

Primary xylemSecondary xylem

Vascular cambium

Secondary phloem

Primary phloem

Periderm(mainly cork cambiaand cork)

PithPrimary xylem

Vascular cambium

Primary phloemCortex

Epidermis

Vascular cambium

4 First cork cambium

Secondary xylem(two years ofproduction)

Pith


Primary xylem

Epidermis

Cortex

2

1

6

Growth

Primary xylem

Secondary xylem

Secondary phloem

Primary phloem

Cork

Phloem ray3 Xylem

ray

Growth

9 Bark

8 Layers of periderm

7 Cork

5 Most recentcork cambium


Secondary phloem


Secondary phloemVascular cambiumLate wood

Early woodSecondaryxylem

Corkcambium

CorkPeriderm

(b) Transverse sectionof a three-year-old stem (LM)

Xylem ray

Bark

0.5 mm0.5 mm


Figure 35.19 Cell division in the vascular cambiumVascularcambium

C X CP

C

XC

XC

P

P

PC

XX P

CX

X

CC

Types of cell division. An initial can divide transversely to form two cambial initials (C) or radially to form an initial and either a xylem (X) or phloem (P) cell.

(a)

Accumulation of secondary growth. Although shown here as alternately adding xylem and phloem, a cambial initial usuallyproduces much more xylem.

(b)


Figure 35.20 Anatomy of a tree trunk

Growth ring

Vascularray

Heartwood

Sapwood

Vascular cambium

Secondary phloem

Layers of periderm

Secondaryxylem

Bark


Figure 35.21 Arabidopsis thaliana

Cell organization and biogenesis (1.7%)DNA metabolism (1.8%)

Carbohydrate metabolism (2.4%)Signal transduction (2.6%)

Protein biosynthesis (2.7%)

Electron transport(3%)

Proteinmodification (3.7%)

Proteinmetabolism (5.7%)

Transcription (6.1%)

Other metabolism (6.6%)

Transport (8.5%)

Other biologicalprocesses (18.6%)

Unknown(36.6%)


Figure 35.22 The plane and symmetry of cell division influence development of form

Division insame plane

Single file of cells forms

Plane ofcell division

Division inthree planes

Cell divisions in the same plane produce a single file of cells, whereas cell divisions in three planes give rise to a cube.(a)

Cube forms

Nucleus

Asymmetrical

cell division

Developingguard cells

Unspecializedepidermal cell


Guard cell“mother cell”


An asymmetrical cell division precedes the development of epidermal guard cells, the cells that border stomata (see Figure 35.17).(b)


Figure 35.23 The preprophase band and the plane of cell division

Preprophase bandsof microtubules

Nuclei

Cell plates

10 µm


Figure 35.24 The orientation of plant cell expansion

Cellulosemicrofibrils

Vacuoles

Nucleus

5 µm


Figure 35.25 The fass mutant of Arabidopsis confirms the importance of cytoplasmic microtubules to plant growth

Wild-type seedling

fass seedling

Mature fass mutant(a)

(b)

(c)


Figure 35.26 Establishment of axial polarity


Figure 35.27 Overexpression of a homeotic gene in leaf formation


Figure 35.28 Control of root hair differentiation by a homeotic gene

When epidermal cells border a single corticalcell, the homeotic gene GLABRA-2 is selectivelyexpressed, and these cells will remain hairless.(The blue color in this light micrograph indi-cates cells in which GLABRA-2 is expressed.)

Here an epidermal cell borders twocortical cells. GLABRA-2 is not expressed,and the cell will develop a root hair.

The ring of cells external to the epi-dermal layer is composed of rootcap cells that will be sloughed off asthe root hairs start to differentiate.

Corticalcells

20 µm


Figure 35.29 Phase change in the shoot system of Acacia koa

Leaves produced by adult phaseof apical meristem

Leaves produced by juvenile phaseof apical meristem


Figure 35.30 Organ identity genes and pattern formation in flower development

Normal Arabidopsis flower. Arabidopsisnormally has four whorls of flower parts: sepals (Se), petals (Pe), stamens (St), and carpels (Ca).

Abnormal Arabidopsis flower. Reseachers haveidentified several mutations of organ identity genes that cause abnormal flowers to develop. This flower has an extra set of petals in place of stamens and an internal flower where normal plants have carpels.

(a)

(b)

Ca

St

Pe

Se

Pe

Pe

Se

Pe

Se


Figure 35.31 The ABC hypothesis for the functioning of organ identity genes in flower development

Sepals

PetalsStamens

Carpels

C geneactivityB + C

geneactivity

A + Bgene

activity

A geneactivity

(a) A schematic diagram of the ABChypothesis. Studies of plant mutationsreveal that three classes of organ identitygenes are responsible for the spatial patternof floral parts. These genes are designated A,B, and C in this schematic diagram of a floralmeristem in transverse view. These genesregulate expression of other genesresponsible for development of sepals,petals, stamens, and carpels. Sepals developfrom the meristematic region where only Agenes are active. Petals develop where bothA and B genes are expressed. Stamens arisewhere B and C genes are active. Carpels arisewhere only C genes are expressed.

Activegenes:

Whorls:

StamenCarpel

Petal

SepalWild type Mutant lacking A Mutant lacking B Mutant lacking C

(b) Side view of organ identity mutant flowers. Combining the modelshown in part (a) with the rule that if A gene or C gene activity is

missing, the other activity spreads through all four whorls, we can explain thephenotypes of mutants lacking a functional A, B, or C organ identity gene.

A A C C C C A A CCCCCCCC A A C C C C A A A B B A A B B AB B B B B B B B A A A A

AB

C

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