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
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