bi 151 what are plants??? plant morpho-anatomy lecture 1 jade vine shoot and root systems •above...

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Bi 151

Plant Morpho-anatomy

Lecture 1

Plants: General Structural Features

Jan Lorie M. Robil, M.Sc.

What are plants???

Kingdom Plantae (plants)

1. Multicellular

2. Autotrophs (chloroplasts)

3. Cellulose in cell walls

4. Eukaryotic (true nucleus; DNA enclosed

by a membrane)

What are some structural

features of plants?

1. Cellulosic cell walls

2. Chloroplasts

3. Appearance

a. Can include stems, leaves, and roots

b. Some lack true stems, leaves, and roots

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Flowering Plants

ANGIOSPERMS

Magnoliids Eudicots

Monocots

White Champaca

Waling-waling Jade vine

Shoot and Root systems

• above or below ground

• no clear demarcation

• morphology and anatomy are somewhat

continuous

• adventitious parts

Shoot system

Leaf Stem

Basic Morphology

Leaves

Casuarina equisetifolia

Schefflera odorata Alamanda cathartica

Jatropha curcas

Leaves-modifications

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Leaf shape A. Elliptic

B. Obovate

C. Ovate

D. Lanceolate

E. Reniform

F. Cordate

G. Trullate

H. Deltoid

I. Rhomboid

J. Amplexicaul

K. Perfoliate

L. Connate-perfoliate

M. Ensiform

N. Ligulate

O. Sagittate

P. Plated

Leaf shape

Psidium guajava Citrus sp.

Bauhinia purpurea Hibiscus sp.

Leaf venation

Eudicot Miconia sp.

acrodromous venation

Leaf venation

Monocot Bambusa sp.

parallel venation

Stem Stem - modifications

tubers stolon

rhizome tendril

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Roots Plant Cells and Tissues

An Evolutionary Perspective

Plants are structurally complex

• All the cells of a plant are genetically

identical

• But the information is expressed in

different ways in different places at

different times in a synchronized fashion

... but plants arose from structurally simple

ancestors

Plants Arose from the Green Algae

• Silurian Period Over 400 Million Years Ago

Evidence That Plants Arose from

the Green Algae

• Pigmentation

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the Green Algae

• Pigmentation

• Cellulose in their

cell walls


the Green Algae

• Pigmentation

• Cellulose in their cell walls

• Starch stored in the plastid

• Some green algae undergo cell division by means of a phragmoplast


the Green Algae

• Pigmentation

• Cellulose in their cell walls

• Starch stored in the plastid

• Some green algae undergo cell division by means of a phragmoplast

The structural complexity of

plants evolved in response to the

challenges of life on land

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Plants can be

considered simply

as a group of the

green algae that have

become adapted for

life on land.

Challenges for Colonizing the Land

Dehydration

Support

Transport of

Water and Minerals

Transport of

Photosynthate

Fertilization

Solutions (Adaptations)

Dehydration

Support

Transport of

Water and Minerals

Transport of

Photosynthate

Fertilization

Dermal tissue; Cuticle

Secondary Walls

Xylem Tissue

Phloem Tissue

Reproductive organs

Vascular plants are made up of

three tissue systems which are

represented in each plant organ.

Ground Tissue System

• Includes cells and tissues like those found

in the green algae

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Dermal Tissue System

• found in all plants

Dermal tissue of

a hornwort, a

non-vascular

plant

Vascular Tissue System

• Are tissues

that transport

substances

long distances

in a plant.

Green

Algae

All

Plants

Cells and Tissues of the Ground

Tissue System

Parenchyma Sclerenchyma Collenchyma

Parenchyma

• Parenchyma cells are living,

undifferentiated plant cells usually lacking a

secondary cell wall.

• Typically, parenchyma cells are totipotent. – Each cell retains the ability to grow into a

whole plant.

– This makes genetic engineering much easier

with plants than with animals.

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Parenchyma Tissue

• Function

– Growth/Wound Healing/Reproduction

Parenchyma Tissue

• Functions


– Photosynthesis

Parenchyma Tissue

• Functions


– Photosynthesis

– Storage

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Collenchyma Tissue

• Is a simple tissue consisting only of

collenchyma cells

• Collenchyma cells are living cells with

thickened primary walls.

• They never have secondary walls.

Collenchyma Tissue

• Support in herbaceous tissues

• Flexebility

Collenchyma Tissue

• Support in herbaceous tissues

400x

Collenchyma acts in opposition to turgor pressure,

And, together, they lend rigidity to the plant

Sclerenchyma Tissue

• Sclerenchyma (hard) cells develop a secondary wall, and are not involved in transport.

• Sclerenchyma lends integrity to plant tissues, and/or they serve to support and protect the plant.

• There are two types of sclerenchyma cells.

– Fibers

– Sclereids

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Fibers Sclereids

Brachysclereids

Unbranched Sclereids

Branched Sclereids (astrosclereids) Ground Tissue System

• Includes:

– Parenchyma cells and tissue

– Collenchyma cells and tissue

– Sclerenchyma cells and tissue

• These are not exclusively found in the

ground tissue


• In herbaceous plants, an epidermis makes

up the dermal tissue system.

• Cell types of the epidermis

– Basal Cells of the Epidermis


• Basal Cells of the Epidermis of the Shoot

As the cuticle is air-tight as well as water-proof it must

be perforated to allow for gas exchange.

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If these openings are bounded by guard cells

then these are called stomata.


• Herbaceous plants have an epidermis. In

the shoot, the epidermis includes

– basal cells and guard cells


• Mature woody plant

– the epidermis is replaced by a periderm.

Periderms include cork which functions like

the epidermis in retaining water.

The word “cell” was first used in a biological

context in 1665 by Robert Hooke to describe

the units that make up the tissue of a wine cork.

Cork Tissue is Water-proof

Suberin


• Tissues and structures

– Herbaceous growth (primary)

• Epidermis (including basal cells and guard cells)

– Cuticle (cutin)

– Wood growth (secondary)

• Periderm with cork tissue

– Suberin

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Green

Algae

All

Plants

Vascular

tissue is

necessary

for a plant

to become

tall.

Vascular plants

have cells with secondary

walls that include lignin

But why not simply remain short?

Because of competition for light.

The Vascular Tissue System

includes two types of tissues .

Xylem Phloem

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• complex tissues

– they are made up of more than one cell type.

– Simple tissues are made of one cell type such

as parenchyma, collenchyma and

sclerenchyma tissues.

Xylem

• Moves water

and minerals

up the plant

• and provides

support to

the plant.

Phloem

Moves

photosynthate

(usually sucrose)

around the plant

MacArthur Highway through Dau, Mabalacat, Pampanga Province, Luzon Island, Philippines

Evolution of Xylem and Phloem

The evolution of phloem is not specific to the challenges of

life on land, but was simply a response to the challenge of

becoming a large photo-autotroph.

Large photo-autotrophs invariably need to fuel a significant

amount of non-photosynthetic tissue.

The evolution of xylem is a direct response to the unique

challenges of life on land relating to water transport and

support.

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Xylem

• Xylem is a complex tissue that includes tracheary elements

– Tracheary elements are dead at maturity and have always have a secondary wall.

– Water moves through these cells by mass flow.

– The pressure inside tracheary elements is less than the ambient pressure and the secondary walls prevent the cells from collapsing.

Cohesion-Tension Theory

• Water is pulled up the tracheary elements,

because water molecules stick together

(cohere) via hydrogen bonds

• adhesion of water molecules to inner cell

wall surface

Role of Secondary Walls

• Secondary walls keep

the tracheary

elements from

collapsing

• help support the plant

• forms pits (holes) in

the wall

Vessel elements in an

elongating plant stem

Tracheary Elements

• Two types

– Vessels

– Tracheids

• both have pits (holes)

• but only vessels have

perforations A perforation is an area between

tracheary elements where both the

primary and secondary wall has

been removed.

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Vessels

• Vessels have independently evolved in six

different plant groups.

– Flowering plants have them (Angiosperms)

– Conifers Don’t (Gymnosperms)

Phloem

• a complex tissue that includes sieve

elements

Sieve Cells (Conifers) Sieve-Tube Elements

(Angiosperms)

Sieve-Tube Elements

• made up of

sieve-tube members

– have sieve plates

– and are associated

with companion cells

Gymnosperms have a

different type of sieve

element called a sieve cell

- Associated with albuminous cells


Xylem

Always includes tracheary elements

May have

Parenchyma

Tracheids and/or vessel elements

Fibers


Phloem Always has sieve elements

May also have

If sieve-tube members then also companion cells

If sieve cells then also albuminous cells

Parenchyma cells

Fibers

bi 151 what are plants??? plant morpho-anatomy lecture 1 jade vine shoot and root systems •above...

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