Plant Cells

The Body’s OrganizationEach level represents a different compartment

Cells

Tissues

Tissue Systems

Organs

Organelles

Organism

What is a Cell?

What is a Cell?• The smallest unit that conforms to the

definition of life

1. Reproduction

2. Response to stimuli

3. Metabolism

4. Movement

5. Complexity of Organization

6. Adaptation to the environment

Major Evolutionary Events in the Origin of Life

Primordial Soup

First CellsProkaryotes

“the animation of matter”3.5 bya

Eukaryotic Cells1.7 bya

Multicellular Organisms700-500 mya

Eubacteria

Archaebacteria

Animal

Fungi

Plant

Protist

Commonancestor

Domains:

Kingdoms:

Eubacteria Archaea Eukarya

Fig. 1.10

There are Two Groups of Cells

• Bacterial Cells (Prokaryotic cells)– The first cell to have evolved– Relatively small and less complex than the…

• Eukaryotic Cells– On average 100X larger than a bacterial cell– Contains organelles: internally more

complex

The Bacterial Cell

Cyanobacteria

The Cyanobacteria are capable of photosynthesis. It is believed that they are responsible for the first oxygen levels in the early atmosphere.

Cyanobacterium: Oscillatoria sp.

Anatomy of a Eukaryotic Plant Cell

Organelles of the cell

1. Cell wall

2. Cell membrane

3. Cytoplasm

4. Cytoskeleton

5. Nucleus– chromosomes

6. Mitochondria

7. Plastids

a. Chloroplast

b. Amyloplast

c. Chromoplast

8. Vacuole

Cell Walls

• Made of carbohydrates (cellulose)

• Protection and structure

• All cells, except animal cells, have cell walls

The Cell Wall• Cell walls are:

– Structural – Provide defense against invading pathogens– Provide pathways for communications

between cells• Structural components:

1. cellulose

2. hemicellulose (glue that holds cellulose fibers together)

3. pectin (stiffens fruit jellies)

4. Proteins

• Cell wall organization– Growing plant cells produce

a primary cell wall, which stretches as the cell grows

– A secondary cell wall may then be produced, inside the primary wall• Strong, thick

– Secondary cell walls set limits to cell growth

• Middle Lamella is the area between adjacent plant cells and is made of pectin

The cell membrane

The cell membrane

• Semi-fluid cell boundary (thick oil)

• controls passage in/out of cell

• Made of 2 lipid layers with proteins on its surface and embedded within the layers

Cytoplasm

• A rich “soup” of carbohydrates, proteins, fats and nucleic acids

• Sometimes referred to as protoplasm

• Watery or gelatin-like substance in which all organelles are suspended

Nucleus

• “Control center”• Genetic

information stored as chromosomes

• The Genome: all the genetic material in a cell

• Nuclear Pores allow passage between the nucleus and the cytoplasm

Plant Chromosomes

Humans 2n = 46

Corn 2n = 20

Cotton 2n = 52

Wheat 6n = 42

Redwood tree 2n = 66

Sugar Cane 2n = 80

The CYTOSKELETON

• Extensive network of protein fibers

• Functions in• internal support• provides internal

structure to the cell• transport of organelles

and protein vesicles• cell motility

– cilia– flagella

View of Cytoskeleton

• Network of protein fibers

• Provides structure and shape to the cell

• Movement of the cell

• Internal movement of organelles and other molecules

Flagella

The MightyMitochondrion! Powerhouse

of the Cell

ATP= energy

Mitochondria• “powerhouse of the

cell”• ATP production• Cell “breathing” is

called cellular respiration

• The mitochondrion has its own Genome

Cellular respiration: converts sugars to energy (ATP)

Plastids• Contain

pigments or storage products

1. Chloroplasts

2. Chromoplasts

3. Amyloplasts

Cells of a red pepper

Chloroplast • Vary in size and

shape

• Thylakoids– where photosynthesis

takes place

• Stroma– Calvin cycle– sugar synthesis

• The chloroplast has its own genome

Photosynthesis converts light energy to chemical energy (sugars)

Chloroplasts of Elodea

and Spyrogyra

Amyloplasts store Starch

Vacuoles• stores water, ions,

and nutrients • receptacles for waste

products• regulates turgor

pressure through osmosis

The Central Vacuole of Plant Cells

Eubacteria

Archaebacteria

Animal

Fungi

Plant

Protist

Commonancestor

Domains:

Kingdoms:

Eubacteria Archaea Eukarya

The Algae

• Many Algae live life as a single cell, but some are

• Multicellular like the seaweeds

• Members of Kingdom Protista

• Primary producers of aquatic ecosystems

Spirogyra

• Watersilk• Float in masses at the

surface of quiet waters• Contain ribbon-shaped

chloroplasts• Each chloroplast

contains a pyrenoid• Pyrenoids contain

enzymes for starch synthesis

Euglena

• They live in fresh water streams and ponds, and are especially common in warm seasons when they may form a green scum on the surfaces of small ponds or drainage ditches.

• Euglenas have spindle-shaped bodies, and range in size from 1/1000 to 1/100 of an inch (0.025 to 0.254 millimeter) long.

Volvox• Volvox is a colonial algae• It is a complete hollow ball of cells. • Note the smaller daughter colonies

that are beginning to form within the parent body.

• Each cell has 2 flagella which helps the entire colony swim.

Diatoms

• Best known and economically most important algae– Cold and warm waters– Fresh and marine– Damp cliffs, sides of

buildings, bark of trees, bare soil

• The cell resides inside a glass box

Diatoms

What often looks like an oil slick is a bio-film of diatoms

Diatoms: Melosera

Plant Tissues

• Parenchyma• Collenchyma• Sclerenchyma

– fibers and sclerids

• Vessels• Tracheids• Sieve tube

members• Companion cells• Egg (ovum)• Sperm

Examples of the Different Types of

Plant Cells

The Parenchyma Cell

• The generic plant cell• Most abundant and

versatile• Function:

– storage• flesh of fruit• storage in roots and

seeds

– basic metabolism

• They can change and become other cells (differentiation)

• Alive at maturity• Primary cell wall

The Collenchyma

Cell

• “glue” cells• Flexible support• Found in growing

shoots, stems, & leaves

• Differentiate from parenchyma cells

• Alive at maturity• Primary and

secondary cell walls• Ex: resilient strings

found in celery

Nucleus(b) Cytoplasm Vacuole

Thickened cornerof cell wall

Sclerenchyma• Rigid cells• Function: support

and strengthen non extending regions of a plant like mature stems

• Thick, non stretchable secondary cell walls

• Dead at maturity• Two Types:

1. Fibers– long, slender, occur in

strands– Cotton– Hemp– Flax (Linen)

2. Sclerids– short, varying shape,

occur in groups– Gristle in pears

Plants Eggs and Sperm

CellsTissues

• Like animal cells, plant cells are organized into tissues

• Tissues are groups of cells that form a structural and functional unit– Simple tissues have one cell type– Complex tissues have two or more cell

types

Tissues Tissue System

• Tissues are organized into tissue systems

• Vascular plants have three tissue systems– Ground tissue

• Energy transformation, storage and support

– Vascular tissue• Water and nutrient conduction system

– Dermal tissue• Covering for the plant body

Apical Meristem

protoderm

procambium

ground meristem

dermal

vascular

ground

epidermis

periderm

xylem

phloem

parenchyma

collenchyma

sclerenchyma

parenchyma

tracheids

vessels

parenchyma

fibers

sieve tube members

companion cells

parenchyma

fibers

parenchyma

collenchyma

sclereids

fibers

Primary Meristem Tissue System Tissues Cells

Cell Differentiation in Plants

• Building a House

1. Foundation is laid

2. Construction of the frame

3. Installation of plumbing, heating, etc

4. Waterproof walls and roof

5. Food stored in appropriate places

• Building a plant1. Meristems give rise to all

tissues2. Three tissue systems give

rise to the major organs of a plant

3. Installation of the vascular tissue (plumbing)

4. Installation of dermal tissues– covering, skin

5. Installation of ground tissue– parenchyma

Meristems• Meristems are regions of cell division• Main difference between animals and plants• Birds and mammals stop growing at maturity,

although certain cells get replenished (skin)• Plants have the ability to keep growing their

entire lives• Meristems make it possible to grow a new

plant from a cutting • Growth in plants is the counterpart (to some

extent) to movement in animals

Apical Meristems• Shoot apical

meristem• Root apical meristem• Found at the tips of

roots and shoots• Increase the length of

a plant

Apical meristems give rise to:

• Three primary meristems1. Ground meristem

– Give rise to ground tissues

2. Protoderm– Give rise to “skin”

coverings

3. Procambium– Give rise to plumbing

of the plant

Other Meristems:Lateral meristems

• Secondary Growth

• Add girth (width) by producing wood and bark

Other Meristems:Intercalary Meristems

• Why grass keeps growing back after you cut it.

• Grasses and related plants do not have lateral meristems

• Intercalary meristems add to the plants length

The Tissue Systems Give Rise to the Organs of a Plant

• Tissues that “ground” the plant

• Fundamental tissues of a plant

1. parenchyma

2. collenchyma

3. sclerenchyma

Ground Tissue

Ground Tissues: Parenchyma

• cells assume various shapes and sizes

• contain starch grains or other storage granules

• oils• tannins (tanning or dyeing

substances)• crystals• various other secretions

Collenchyma

Parenchyma

Ground Tissues: Collenchyma• are alive at maturity

• cell walls are thicker and more uneven

• typically longer than wide

• tend to be found under the epidermis

• provide flexible support

Sclerenchyma

• Tissues (cells) have thick, tough secondary cell walls made of lignin

• Dead at maturity

• Function in support1. sclerids

2. fibers

Fibers are used for clothing

• Cotton• Linen• Bamboo• Hemp

The Dermal and Vascular Tissue Systems are made of Complex Tissues

• Tissues that are made of more than one cell type

• Dermal Tissues– epidermis – endodermis

• Vascular tissues– Xylem – Phloem

Dermal Tissues

• dermal tissues cover the organs of a plant. They are analogous to skin.

• epidermis• outermost layer of cells• usually one cell layer thick• epidermal cells have a layer of cutin (cuticle)

– resistant to bacteria and other disease organisms

Cuticle Wax

• Wax Myrtle• Myrica cerifera• waxes

obtained from boiling the leaves is used to make bayberry candles

Epidermis is made of many types of cells1. Guard cells form stomata

2. Trichomes– Outgrowths – ‘hairs’– Some leaf trichomes use to keep

animals away – Some used to eliminate salt– Some thought to increase

reflection to reduce stem/leaf temperature

– Root hairs are a type of trichome, increase surface area to increase uptake of nutrients

3. Glands

Root Hairs are extensions of

epidermal cells

Dermal Tissues: Epidermis

• Glands secrete substances that protect the plant

• secrete nectar• digestive glands• Sundews• trigger hairs of a

Venus Flytrap

Prickles grow out of the epidermis

Complex Tissue: Vascular Tissues• Xylem Tissue

– transports water and dissolved substances through the plant to all its organs

1. parenchyma cells

2. fibers

3. tracheids

4. vessels

5. rays

Xylem

• Tracheids• Have thick secondary cell walls• dead at maturity• tapered at the end• contain pits

– areas where no 2° cell wall is laid down

Xylem • Vessels• Have thick

secondary cell walls• dead at maturity• long tubular cells

with grate-like openings at the end

• contain pits– areas where no 2°

cell wall is laid down

Cell wall

Lumen

(a) (b)

Pits

End wall withperforations

Tracheid Vessel

Many cone bearing trees and other non-flowering plants

• Xylem is made of tracheids only

• soft wood of pines• tracheids often

have spiral thickenings on them

• Vessels make the wood of flowering trees “hard” wood

Complex Tissue:Vascular Tissues

• Phloem Tissue– transports dissolved food

(sugars) through the plant to all its organs

1. sieve tube members

2. companion cells

3. parenchyma

4. fibers

5. rays

phloem

Companion cell

(c) (d)

Plasmodesma

Lateral sievearea

Phloemparenchyma

cells

Sieve tubemember

Sieve plate

Sieve Tube MemberPhloem tissue

Sieves and Sieve tube cells

Phloem: Companion cells• Companion cells are

“companions” to sieve tube cells

• Because sieve tube cells have no nuclei, the companion cells provide all the nutrients to the sieve tube cell