Figure 35.10 Review of General Plant Cell Structure

Shoot System

Root System

Root system

- anchors the plant

- penetrates the soil and absorbs water and minerals

- stores food

Shoot system

- produces sugars by photosynthesis

- carries out reproduction

Shoot and Root Systems

water & minerals

sugar

SHOOT SYSTEM

ROOT SYSTEM

Shoot and root systems are interdependent

Plant Tissue Systems

VASCULAR TISSUES

GROUND TISSUES

SHOOT SYSTEM

ROOT SYSTEM

EPIDERMIS

• Ground tissue system

• Vascular tissue system

• Dermal tissue system

Meristems – Where Cells For New Organs Originate

• Regions where cell divisions produce plant growth

• Apical meristems– Lengthen stems and roots– Responsible for primary growth

• Lateral meristems– Increase width of stems– Responsible for secondary growth

Apical Meristems

activity atmeristems

new cellselongateand start todifferentiateinto primarytissues

procambium primary vascular tissues

protoderm epidermis

Cells that form at apical meristems:

ground meristem ground tissues

Lengthen shoots and roots

Lateral Meristems

vascular cambium secondary vascular tissues

periderm cork cambium

thickening

Increases girth of older roots and stems

Cylindrical arrays of cells

Figure 35.7 The three tissue systems

The Three Tissue Systems in Plants

Simple Tissues

Made up of only one type of cell

Parenchyma

Collenchyma

Sclerenchyma

collenchymaparenchyma sclerenchyma

Morphology of Three Simple Tissue Types

Figure 35.11 The three major categories of plant cells

Parenchyma: A Simple Tissue

• Comprises most of a plant’s soft primary growth

• Cells are pliable, thin walled, many sided

• Cells remain alive at maturity

and retain capacity to divide

• Mesophyll is a type of

parenchyma that contains

chloroplasts

Collenchyma: A Simple Tissue

• Specialized for support for primary tissues

• Cells are elongated, with walls (especially corners)

thickened with pectin

• Makes stems strong

but pliable

• Cells are alive at maturity

Sclerenchyma: A Simple Tissue

• Supports mature plant parts• Protects many seeds• Cells have thick, lignified walls and are

dead at maturity• Two types:

– Fibers: Long, tapered – cells– Sclereids: Stubbier cells

Complex Tissues

Composed of a mix of cell types

Xylem

Phloem

Epidermis

Xylem

• Conducts water and dissolved minerals

• Conducting cells are dead and hollow at maturity vessel

membertracheids

Figure 35.8 Water-conducting cells of xylem

Phloem: A Complex Vascular Tissue

• Transports sugars

• Main conducting cells are sieve-tube members

• Companion cells assist in the loading of sugars

sieve plate

sieve-tubemember

companioncell

Figure 35.9 Food-conducting cells of the phloem

Figure 36.17 Pressure flow in a sieve tube

Epidermis: A Complex Plant Tissue

- Covers and protects plant

surfaces

- Secretes a waxy,

waterproof cuticle

-In plants with

secondary growth, periderm

replaces epidermis

Monocots and Dicots – same tissues, different

features

Parallel veinsNetlike veins

3 pores1 pore

4 or 5 floral parts

3 floral parts

1 cotyledon 2 cotyledons

Vascular bundles dispersed

Vascular bundles in ring

Stems –

organs consisting of an alternatingsystem of nodes, the points at which leaves are attached, and internodes, the stem segments between nodes.

• the main functions of the stems includeconducting sugars and water and holdingleaves up into the sunlight

Monocot and Dicot Stems (Two Divisions of Angiosperms)

Dicot StemMonocot Stem

Bud = undeveloped shoot of meristematic tissue

Internodespaces betweenleaf attachments

Leaves

Axillary bud at node(can form lateral shoots)

Longitudinal section of terminal bud

Shoot Development

ground meristem

primary xylempithprocambriumcortex

procambrium

protoderm

shoot apicalmeristem

primary phloem

Internal Structure of a Dicot Stem

- Outermost layer is epidermis

- Cortex lies beneath epidermis

- Ring of vascular bundles separates the cortex from the pith

- The pith lies in the center of the stem

Internal Structure

of a Monocot

Stem

• The vascular

bundles are

scattered

throughout the

ground tissue

• No division of

ground tissue into

cortex and pith

Secondary Growth

• Occurs in perennials

• A ring of vascular cambium produces

secondary xylem and phloem

• Wood is the accumulation of these

secondary tissues, especially xylem

Woody Stemperiderm (consists ofcork, cork cambium,and secondary cortex)

secondaryphloem

BARK

HEARTWOOD

SAPWOOD

vascular cambium

Figure 35.23 Anatomy of a tree trunk

Annual Rings• Concentric rings of secondary xylem• Alternating bands of early and late

wood• Early wood

–Xylem cells with large diameter, thin walls

• Late wood–Xylem cells with smaller diameter,

thicker walls

Types of Wood• Hardwood (oak, hickory)

–Dicot wood–Xylem composed of vessels,

tracheids, and fibers• Softwood (pine, redwood)

–Gymnosperm wood–Xylem composed mostly of

tracheids–Grows more quickly

Adapted for Photosynthesis

• Leaves are usually thin

– High surface area-to-volume ratio

– Promotes diffusion of carbon dioxide in, oxygen out

• Leaves are arranged to capture sunlight

– Are held perpendicular to rays of sun

– Arrange so they don’t shade one another

Leaf StructureUPPER

EPIDERMIS

PALISADEMESOPHYLL

SPONGYMESOPHYLL

LOWEREPIDERMIS

one stoma

cuticle

O2CO2

xylem

phloem

Stoma with guard cells

Figure 35.19 Leaf anatomy

Mesophyll:Photosynthetic Tissue

• A type of parenchyma

tissue

• Cells have chloroplasts

• Two layers in dicots

–Palisade mesophyll

–Spongy mesophyll

Parenchyma

Collenchyma

Leaf Veins: Vascular Bundles

• Xylem and phloem –

often strengthened with fibers

• In dicots, veins are netlike

• In monocots, they are parallel

Root Structure

• Root cap covers tip

• Apical meristem produces the cap

• Cell divisions at the apical meristem cause the root to lengthen

• Farther up, cells differentiate and mature

root apical meristem

root cap

Root SystemsTap

Fibrous

Lateral Rootsgrow from the Tap Root

Primary Growth of a Root

pericycle

phloem

xylem

root hair

endodermis

epidermis

cortex

xylem

phloem

endodermis

pericycle

cortex epidermis

Cross Section of a Root

Internal Structure of a Root

• Outermost layer is epidermis

• Root cortex is beneath the epidermis

• Endodermis, then pericycle surround

the vascular cylinder

• In some plants, there is a central pith

Root Hairs and Lateral Roots

• Both increase the surface area of a

root system

• Root hairs are tiny extensions of

epidermal cells

• Lateral roots arise from the pericycle

and must push through the cortex

and epidermis to reach the soil

newlateralroot

Figure 35.16 The formation of lateral roots

Lateral Root

Figure 36.7 Lateral transport of minerals and water in roots

Figure 36.6 Compartments of plant cells and tissues and routes for lateral transport

Transport Proteinsin the plasma membrane regulatetraffic between the cytosol and the cellwall

The symplast is the continuum of cytosolconnected by

plasmodesmata.The apoplast is the continuumof cell walls and extracellular

spaces.

Figure 35.15 Organization of primary tissues in young roots

PropRoots

Pandanus Tree WithProp Roots

Prop Roots

Buttress Roots

BanyanTree WithAerial Roots