Chapter 29: Plant Tissues - Goodhue€¦ · ground tissues primary vascular tissues The cellular descendants of apical meristems divide, grow, and differentiate. They form three primary

Chapter 29: Plant Tissues

Shoots and Roots • Shoots (Leaves and Stem)

– Produce food by photosynthesis

– Carry out reproductive functions

• Roots

– Anchor the plant

– Penetrate the soil and absorb water and

dissolved minerals

Shoot Apical Meristem

primary

meristems

active

epidermis, ground

tissues, primary

vascular tissues

forming

epidermis, ground

tissues, primary

vascular tissues

forming

primary

meristems

active

Root Apical Meristem

Fig. 29-3a, p.494

Protoderm

Ground meristem

Procambium

epidermis

ground tissues

primary vascular tissues

The cellular descendants of apical meristems divide, grow, and differentiate. They

form three primary meristems, the activity of which lengthens shoots and roots:

Fig. 29-3a1, p.494

vascular cambium

cork cambium

Lateral Meristems

thickening

Fig. 29-3b, p.494

Angiosperm Body Plan

VASCULAR TISSUES

GROUND TISSUES

SHOOT SYSTEM

ROOT SYSTEM

EPIDERMIS

Ground tissue

system

Vascular tissue

system

Dermal tissue

system

Fig. 29-2, p.494

Monocots and Dicots:

Parallel veins Netlike veins

3 pores 1 pore

4 or 5

floral

parts

3 floral

parts

1 cotyledon 2 cotyledons

Vascular

bundles

dispersed

Vascular

bundles

in ring

Inside seeds, two

cotyledons seed

leaves of embryo

Usually four or

five floral parts

(or multiples of

four or five)

Leaf veins

usually in a

netlike array

Three pores or

furrows in the

pollen grain surface

Vascular bundles

organized as a ring

in ground tissue

Inside seeds, one

cotyledon seed leaf

of embryo

Usually three

floral parts (or

multiples of

threes)

Leaf veins usually

running parallel

with one another

One pre or furrow in

the pollen grain

surface

Vascular bundles

distributed throughout

ground tissue Fig. 29-4, p.495

Parenchyma: A Simple Tissue

• Most of a plant’s soft primary growth

• Pliable, thin walled, many sided cells

• Cells remain alive at maturity and retain

capacity to divide

• Mesophyll is a type that contains

chloroplasts

stem epidermis

simple and complex tissues inside the stem

parenchyma

vessel of

xylem phloem

fibers of

sclerenchyma

Fig. 29-6, p.496

Collenchyma: A Simple Tissue

• Specialized for support for primary tissues

• Makes stems strong but pliable

• Cells are elongated

• Walls thickened with pectin

• Alive at maturity

Collenchyma: A Simple Tissue

• Supports mature plant parts

• Protects many seeds

• Thick, lignified walls

• Dead at maturity

• Two types:

– Fibers: Long, tapered cells

– Sclereids: Stubbier cells

collenchyma parenchyma lignified secondary wall

Fig. 29-7, p.496

Complex Tissues

Composed of a mix of cell types

Xylem

Phloem

Epidermis

Xylem

Conducts water

and dissolved

minerals up the

shoot

Conducting cells

are dead and

hollow at maturity vessel

member tracheids

one

cell’s

wall

pit in

wall

sieve plate

of sieve

tube cell

companion

cell

a b c

Fig. 29-8, p.497

Phloem: A Complex Vascular Tissue

• Transports sugars

down the shoot

• Main conducting

cells are sieve-tube

members

• Companion cells

assist in the loading

of sugars

sieve plate

sieve-tube

member

companion

cell

Epidermis: A Complex Plant Tissue

• Covers and protects plant surfaces

• Secretes a waxy, waterproof cuticle

• In plants with secondary growth,

periderm replaces epidermis

leaf surface cuticle epidermal cell photosynthetic

cell

Fig. 29-9, p.497

Meristems

• 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 at

meristems

new cells

elongate

and start to

differentiate

into primary

tissues

activity at

meristems

new cells

elongate

and start to

differentiate

into primary

tissues

Root apical meristem

Shoot apical meristem

Fig. 29-10a1, p.498

immature leaf

shoot apical meristem

lateral bud forming

vascular tissues

pith

cortex

Fig. 29-10a2, p.498

immature leaf

shoot apical

meristem

descendant

meristems

(orange)

Fig. 29-10b, p.498

Lateral Meristems

• Increase girth of older roots and stems

• Cylindrical arrays of cells

vascular cambium cork

cambium

thickening

Figure 29.20.a

Page 504

immature leaf

shoot apical meristem descendant

meristems

(orange)

Stepped Art

Fig. 29-10b-d, p.498

primary phloem

primary xylem

pith

cortex

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 distributed

throughout the ground

tissue

• No division of ground

tissue into cortex and

pith

Figure 29.11.b

Page 499

cortex

epidermis

vascular

bundle

pith

vessel

in xylem

meristem

cell

sieve tube

in phloem

companion

cell in

phloem

Fig. 29-11a, p.499

Common Leaf Forms

petiole

blade

axillary

bud

node

blade

sheath

node

DICOT MONOCOT

Figure 29.12.a,b

Page 500

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

– Arranged so they don’t shade one another

POPLAR

(Populus)

OAK

(Quercus)

MAPLE

(Acer)

leaflet

RED

BUCKEYE

(Aesculus)

BLACK

LOCUST

(Robina)

HONEY LOCUST

(Gleditsia)

Fig. 29-12c,d, p.500

Leaf Structure

UPPER

EPIDERMIS

PALISADE

MESOPHYLL

SPONGY

MESOPHYLL

LOWER

EPIDERMIS

one stoma

cuticle

O2 CO2

xylem

phloem

Figure 29.14.b

Page 501

leaf blade

leaf vein

stem

Leaf Vein

(one vascular

bundle) cuticle

Upper

Epidermis

Lower

Epidermis

Palisade

Mesophyll

Spongy

Mesophyll

50m

xylem

phloem

cuticle-coated cell

of lower epidermis

one stoma (opening

across epidermia)

Oxygen and

water vapor

diffuse out

of leaf at

stomata.

Carbon

dioxide in

outside air

enters leaf at

stomata.

Water, dissolved mineral ions from roots and stems move into leaf vein (blue arrow)

Photosynthetic

products (pink

arrow) enter

vein, will be

transported

throughout

plant body

Fig. 29-14, p.501

Leaf Veins: Vascular Bundles

• Xylem and phloem; often

strengthened with fibers

• In dicots, veins are netlike

• In monocots, they are parallel

Fig. 29-15a, p.501

Leaf Veins

Fig. 29-15b, p.501

Leaf Veins

Root Systems

Taproot system of

a California poppy

Fibrous root system

of a grass plant Figure 29.19

Page 503

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 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 Figure

29.16.a

Page 502

primary xylem

primary phloem

epidermis

VASCULAR

CYLINDER

cortex

pith

Fig. 29-17, p.503

Fig. 29-18, p.503

Function of Endodermis

• Ring of cells surrounds vascular cylinder

• Cell walls are waterproof

• Water can only enter vascular cylinder by moving

through endodermal cells

• Allows plant to control inward flow

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

new

lateral

root

Fig. 29-19a, p.503

Fig. 29-19b, p.503

Secondary Growth

• Occurs in all gymnosperms, some

monocots, and many dicots

• A ring of vascular cambium produces

secondary xylem and phloem

• Wood is the accumulation of these

secondary tissues, especially xylem

Fig. 29-20, p.504

primary xylem

primary phloem

VASCULAR CAMBIUM

VASCULAR CAMBIUM

secondary xylem

secondary phloem

stem surface

Fig. 29-20b, p.504

Secondary Growth

Figure 29.20.c

Page 504

Ongoing cell divisions

enlarge the inner core of

secondary xylem and

displace vascular cambium

toward the stem

pericycle

procambium

cortex

primary phloem

epidermis

Fig. 29-22a, p.505

endodermis

primary xylem

Woody Roots

vascular cambium produced by pericycle

vascular cambium produced by procambium

secondary xylem

secondary phloem

vascular cambium

vascular ray

cortex, epidermis slough off

crushed primary phloem

pericycle derivatives

epidermis cortex

endodermis pericycle

primary xylem

primary phloem

procambium

Stepped Art

Fig. 29-22, p.505

Fig. 29-23, p.506

A Coast

Redwood

periderm (includes

cork cambium, cork,

new parenchyma)

secondary

phloem

BARK

vascular cambium

HEARTWOOD SAPWOOD

Fig. 29-24a, p.507

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

Fig. 29-25a, p.507

1587–1589 1606–1612

Fig. 29-27c, p.509

Annual Rings Narrow annual rings mark severe drought

years