Plant Structure

Willow shoot

Plant Parts

Monocot vs Dicot

1. Dermal tissue

2. Vascular tissue

3. Ground tissue

Plant organs are composed of three tissue systems:

Plant Cell StructurePlant Cell StructurePlant Cell StructurePlant Cell Structurecell wallcell wallcell wallcell wall

chloroplastchloroplastchloroplastchloroplast

nucleusnucleusnucleusnucleus

central vacuolecentral vacuolecentral vacuolecentral vacuole

Cell Wall StructureCell Wall StructureCell Wall StructureCell Wall Structure

middle lamellamiddle lamellamiddle lamellamiddle lamella

primary cell wallprimary cell wallprimary cell wallprimary cell wall

secondary cell wallsecondary cell wallsecondary cell wallsecondary cell wall

Cell Wall StructureCell Wall StructureCell Wall StructureCell Wall Structure

plasmodesmataplasmodesmataplasmodesmataplasmodesmata

Plant Cell TypesPlant Cell TypesPlant Cell TypesPlant Cell Types• XylemXylem

–TracheidsTracheids

–Vessel elementsVessel elements

• PhloemPhloem–Sieve-tube Sieve-tube

membersmembers

–Companion cellCompanion cell

• XylemXylem–TracheidsTracheids

–Vessel elementsVessel elements

• PhloemPhloem–Sieve-tube Sieve-tube

membersmembers

–Companion cellCompanion cell

Vascular tissue:

• runs continuous throughout the plant

• transports materials between roots and shoots.– Xylem transports water and dissolved minerals

upward from roots into the shoots. (water the xylem)

– Phloem transports food from the leaves to the roots and to non-photosynthetic parts of the shoot system. (feed the phloem)

Vascular Tissue

The water conducting elements of xylem are the tracheids and vessel elements.

Xylem

XylemXylemXylemXylem• TracheidsTracheids

– CharacteristicsCharacteristics• tapered elongated cellstapered elongated cells• connect to each other through pitsconnect to each other through pits• secondary cell walls strengthened with secondary cell walls strengthened with

ligninlignin• dead at functional maturitydead at functional maturity

– FunctionsFunctions• transport of water plus dissolved mineralstransport of water plus dissolved minerals• supportsupport

• TracheidsTracheids– CharacteristicsCharacteristics

• tapered elongated cellstapered elongated cells• connect to each other through pitsconnect to each other through pits• secondary cell walls strengthened with secondary cell walls strengthened with

ligninlignin• dead at functional maturitydead at functional maturity

– FunctionsFunctions• transport of water plus dissolved mineralstransport of water plus dissolved minerals• supportsupport

XylemXylem• Vessel ElementsVessel Elements

–CharacteristicsCharacteristics• shorter and wider than tracheidsshorter and wider than tracheids• possess thinner cell walls than tracheidspossess thinner cell walls than tracheids• Aligned end-to-end to form long Aligned end-to-end to form long

micropipesmicropipes• dead at functional maturitydead at functional maturity

–FunctionsFunctions• transport of water plus dissolved transport of water plus dissolved

mineralsminerals• supportsupport

• Vessel ElementsVessel Elements–CharacteristicsCharacteristics

• shorter and wider than tracheidsshorter and wider than tracheids• possess thinner cell walls than tracheidspossess thinner cell walls than tracheids• Aligned end-to-end to form long Aligned end-to-end to form long

micropipesmicropipes• dead at functional maturitydead at functional maturity

–FunctionsFunctions• transport of water plus dissolved transport of water plus dissolved

mineralsminerals• supportsupport

Water conducting cells of the xylem

• Food and minerals move through tubes formed by chains of cells, sieve-tube members.–sieve plates

–companion cell

Phloem

PhloemPhloemPhloemPhloem• Sieve-tube MembersSieve-tube Members

– CharacteristicsCharacteristics• living cells arranged end-to-end to form food-living cells arranged end-to-end to form food-

conducting cells of the phloemconducting cells of the phloem• lack lignin in their cell wallslack lignin in their cell walls• mature cells lack nuclei and other cellular mature cells lack nuclei and other cellular

organellesorganelles• alive at functional maturityalive at functional maturity

– FunctionsFunctions• transport products of photosynthesistransport products of photosynthesis

• Sieve-tube MembersSieve-tube Members– CharacteristicsCharacteristics

• living cells arranged end-to-end to form food-living cells arranged end-to-end to form food-conducting cells of the phloemconducting cells of the phloem

• lack lignin in their cell wallslack lignin in their cell walls• mature cells lack nuclei and other cellular mature cells lack nuclei and other cellular

organellesorganelles• alive at functional maturityalive at functional maturity

– FunctionsFunctions• transport products of photosynthesistransport products of photosynthesis

PhloemPhloemPhloemPhloem• Companion CellsCompanion Cells

– CharacteristicsCharacteristics• living cells adjacent to sieve-tube membersliving cells adjacent to sieve-tube members• connected to sieve-tube members via connected to sieve-tube members via

plasmodesmataplasmodesmata

– FunctionsFunctions• support sieve-tube memberssupport sieve-tube members• may assist in sugar loading into sieve-tube may assist in sugar loading into sieve-tube

membersmembers

• Companion CellsCompanion Cells– CharacteristicsCharacteristics

• living cells adjacent to sieve-tube membersliving cells adjacent to sieve-tube members• connected to sieve-tube members via connected to sieve-tube members via

plasmodesmataplasmodesmata

– FunctionsFunctions• support sieve-tube memberssupport sieve-tube members• may assist in sugar loading into sieve-tube may assist in sugar loading into sieve-tube

membersmembers

Food conducting cells of the phloem

Ground tissue fills the interior of the plant. It contains three basic cell types:

– Parenchyma cells

– Collenchyma cells

– Sclerenchyma cells

Ground Tissue

Dermal tissue

Vascular tissue

Ground tissue

ParenchymaParenchyma• CharacteristicsCharacteristics

– least specialized cell typeleast specialized cell type– only thin primary cell wall is presentonly thin primary cell wall is present– possess large central vacuolepossess large central vacuole– generally alive at functional maturitygenerally alive at functional maturity

• FunctionsFunctions– make up most of the ground tissues of the plantmake up most of the ground tissues of the plant– storagestorage– photosynthesisphotosynthesis– can help repair and replace damaged organs by can help repair and replace damaged organs by

proliferation and specialization into other cellsproliferation and specialization into other cells

• CharacteristicsCharacteristics– least specialized cell typeleast specialized cell type– only thin primary cell wall is presentonly thin primary cell wall is present– possess large central vacuolepossess large central vacuole– generally alive at functional maturitygenerally alive at functional maturity

• FunctionsFunctions– make up most of the ground tissues of the plantmake up most of the ground tissues of the plant– storagestorage– photosynthesisphotosynthesis– can help repair and replace damaged organs by can help repair and replace damaged organs by

proliferation and specialization into other cellsproliferation and specialization into other cells

ParenchymaParenchyma

CollenchymaCollenchymaCollenchymaCollenchyma

• CharacteristicsCharacteristics– possess thicker primary cell walls the that possess thicker primary cell walls the that

of parenchymaof parenchyma– no secondary cell wall presentno secondary cell wall present– generally alive at functional maturitygenerally alive at functional maturity

• FunctionsFunctions– provide support without restraining growthprovide support without restraining growth

• CharacteristicsCharacteristics– possess thicker primary cell walls the that possess thicker primary cell walls the that

of parenchymaof parenchyma– no secondary cell wall presentno secondary cell wall present– generally alive at functional maturitygenerally alive at functional maturity

• FunctionsFunctions– provide support without restraining growthprovide support without restraining growth

CollenchymaCollenchyma

SclerenchymaSclerenchymaSclerenchymaSclerenchyma

• CharacteristicsCharacteristics– have secondary cell walls strengthened have secondary cell walls strengthened

by ligninby lignin– often are dead at functional maturityoften are dead at functional maturity– two forms: two forms: fibers and sclereidsfibers and sclereids

• FunctionsFunctions– rigid cells providing support and rigid cells providing support and

strength to tissuesstrength to tissues

• CharacteristicsCharacteristics– have secondary cell walls strengthened have secondary cell walls strengthened

by ligninby lignin– often are dead at functional maturityoften are dead at functional maturity– two forms: two forms: fibers and sclereidsfibers and sclereids

• FunctionsFunctions– rigid cells providing support and rigid cells providing support and

strength to tissuesstrength to tissues

• Two other sclerenchyma cells, fibers and sclereids, are specialized entirely in support.– Fibers are long, slender and tapered,

and usually occur in groups.• Those from hemp fibers are used for making

rope and those from flax for weaving into linen.

– Sclereids, shorter than fibers and irregular in shape, impart the hardness to nutshells and seed coats and the gritty texture to pear fruits.

Fiber CellsFiber Cells

SclereidsSclereids

• Meristems– embryonic tissue.– These cells divide to generate additional cells. – Initials- generative cells that remain in the

meristem.– Derivatives- Those that are displaced from the

meristem,and continue to divide for some time until the cells they produce begin to specialize within developing tissues.

Plant Growth & Development

• Apical meristems: located at the tips of roots and in the buds of shoots, supply cells for the plant to grow in length.

–Primary growth• initial root and shoot growth

• produced by apical meristem

• elongation occurs

• restricted to youngest parts of the plant, i.e, tips of roots & shoots

Locations of Meristematic TissuesLocations of Meristematic TissuesLocations of Meristematic TissuesLocations of Meristematic Tissues

–Secondary growth: thickening of roots and shoots.• Produced by lateral meristems

• Develop in slightly older regions of roots and shoots

• Examples: vascular and cork cambium.

• Lateral meristems: allow the plant to increase in girth

Locations of Meristematic TissuesLocations of Meristematic Tissues

MeristemsMeristems

Types of Primary MeristemsTypes of Primary MeristemsTypes of Primary MeristemsTypes of Primary Meristems

• ProtodermProtoderm: : forms dermal tissue systemforms dermal tissue system

• ProcambiumProcambium: : forms vascular tissue systemforms vascular tissue system

• Ground MeristemGround Meristem: : forms ground tissue systemforms ground tissue system

• ProtodermProtoderm: : forms dermal tissue systemforms dermal tissue system

• ProcambiumProcambium: : forms vascular tissue systemforms vascular tissue system

• Ground MeristemGround Meristem: : forms ground tissue systemforms ground tissue system

• Root Cap: covers root tip & protects the meristem as the root pushes through the abrasive soil during primary growth.– The cap also secretes a lubricating slime.

• Growth in length is concentrated near the root’s tip, where three zones of cells at successive stages of primary growth are located.– zone of cell division– zone of elongation– zone of maturation

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Primary Growth in Roots

• The procambium gives rise to the stele, which in roots is a central cylinder of vascular tissue where both xylem and phloem develop.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Stele

Dicot Root Monocot Root

Monocot Root

Anatomy

Monocot Root

Anatomycortexcortex

epidermisepidermis

endodermisendodermis

pithpith

phloemphloemxylemxylem

pericyclepericyclecortexcortex

pithpith

stelestele

Dicot Root Anatomy

Dicot Root Anatomy

cortexcortex

epidermisepidermis

endodermisendodermis

phloemphloem

xylemxylem

pericyclepericycle

cortexcortex

stelestele

Plant Shoot

Primary Growth of the Shoot

Primary Growth of the Shoot

Stem Anatomy

Monocot StemDicot Stem

Monocot Stem

Anatomy

Monocot Stem

Anatomy

epidermisepidermis

vascular bundlesvascular bundles

ground tissueground tissue

xylemxylem

phloemphloem

parenchyma

sclerenchyma

Dicot Stem Anatomy

Dicot Stem Anatomy

vascularcambiumvascularcambium

xylemxylem

pithpith

cortexcortex

epidermisepidermis

vascular bundlevascular bundle

phloemphloem

Anatomy of a Tree TrunkAnatomy of a Tree Trunk• After several years

of secondary growth, several zones are visible in a stem.

Leaf AnatomyLeaf Anatomy

Typical Dicot Leaf X-Section

Palisade Parenchyma

Spongy Parenchyma

Vascular bundles

Epidermis

Cuticle

Stoma

Guard Cells

Typical Monocot Leaf X-Section

Xylem

Phloem

Bulliform Cells Stoma

EpidermisMidvein Vein Bundle sheath cell

Leaf Stomata: Allow Gas Exchange

Guard cells

Stoma