THE PLANT BODY THE PLANT BODY
THE PLANT BODYTHE PLANT BODY
MeristemsMeristems
In flowering plants cells originate from In flowering plants cells originate from regions of active cell division known as regions of active cell division known as meristems.meristems.
The cells arising from meristems give The cells arising from meristems give rise to the many different cell types that rise to the many different cell types that make up a plant make up a plant
Types of MeristemsTypes of Meristems
Primary MeristemsPrimary Meristems (also called Apical (also called Apical Meristems) result in primary growth - Meristems) result in primary growth - growth in lengthgrowth in length
Secondary MeristemsSecondary Meristems result in result in secondary growth which in growth in secondary growth which in growth in width (increase in diameter)width (increase in diameter)
Apical meristemsApical meristems
Also known as primary meristemsAlso known as primary meristems Found at the tips of all roots and stems Found at the tips of all roots and stems Contribute to the increase in length of Contribute to the increase in length of
the plant which is called primary growth the plant which is called primary growth Give rise to the leaves, and non-woody Give rise to the leaves, and non-woody
stems and rootsstems and roots
Secondary MeristemsSecondary Meristems
Some plants have additional meristems Some plants have additional meristems that result in increases in diameter that result in increases in diameter which is secondary growth. which is secondary growth. • Vascular cambium Vascular cambium • cork cambium cork cambium
Multicellular OrganismsMulticellular Organisms
In multicellular organisms, certain cells are In multicellular organisms, certain cells are specialized in structure and functionspecialized in structure and function
Tissues are specialized cells that perform Tissues are specialized cells that perform specific functions specific functions
Plants composed of three basic tissues Plants composed of three basic tissues categoriescategories• DermalDermal• GroundGround• VascularVascular
Dermal TissueDermal Tissue
Dermal tissues are the outermost layers Dermal tissues are the outermost layers in a plantin a plant
They protect the plant They protect the plant Two types of dermal tissuesTwo types of dermal tissues• Epidermis Epidermis • PeridermPeriderm
EpidermisEpidermis
Outermost layer In Outermost layer In young plants and young plants and non-woody plants non-woody plants
Single layer of Single layer of flatten cellsflatten cells
Cells secrete Cells secrete cutincutin which makes up the which makes up the cuticlecuticle and and prevents water loss prevents water loss
Epidermal Cell
Cuticle
TrichomesTrichomes
Hairs (trichomes) Hairs (trichomes) may be present on may be present on the epidermis. the epidermis.
Sometime abundant Sometime abundant enough so leaves enough so leaves look fuzzylook fuzzy
Trichomes may also Trichomes may also be glandularbe glandular
Hair
Gland
Guard Cells and StomataGuard Cells and Stomata
Pores known as stomata (singular Pores known as stomata (singular stoma) occur on epidermisstoma) occur on epidermis
Gases exchange occurs through Gases exchange occurs through stomatastomata
A pair of sausage-shaped cells, guard A pair of sausage-shaped cells, guard cells, regulate the opening and closing cells, regulate the opening and closing of the stomataof the stomata
Guard Cells and StomaGuard Cells and Stoma
Guard Cell
Stoma (opening)
PeridermPeriderm
In woody plants when the tree increases In woody plants when the tree increases in diameter, the epidermis cracks and is in diameter, the epidermis cracks and is replaced by peridermreplaced by periderm
The periderm consists: The periderm consists: • Cork cellsCork cells• Cork cambiumCork cambium
Cork CellsCork Cells
Outer bark on mature treesOuter bark on mature trees Dead cells with walls containing Dead cells with walls containing
suberin, a waterproofing fatty suberin, a waterproofing fatty substance. substance.
Prevents water loss from underlying Prevents water loss from underlying tissues tissues
Produced by cork cambiumProduced by cork cambium
Ground tissues Ground tissues
Major tissue of non-woody plant organsMajor tissue of non-woody plant organs Perform a variety of functionsPerform a variety of functions The three types of ground tissue:The three types of ground tissue:• ParenchymaParenchyma• CollenchymaCollenchyma• SclerenchymaSclerenchyma
ParenchymaParenchyma
Almost any shape or sizeAlmost any shape or size Loosely arranged with intercellular Loosely arranged with intercellular
spacesspaces Many different functions: Many different functions: • Photosynthetic cells in leaves and green Photosynthetic cells in leaves and green
stems stems • Storage cells in plant organs for starch, Storage cells in plant organs for starch,
sugar, or watersugar, or water
Parenchyma CellsParenchyma Cells
Intercellularspaces
Parenchyma CellsParenchyma Cells
CollenchymaCollenchyma
Support tissue in young plant organsSupport tissue in young plant organs Found in stems, leaves, and petalsFound in stems, leaves, and petals Elongated cells with unevenly thickened Elongated cells with unevenly thickened
primary cell walls with the walls thickest primary cell walls with the walls thickest at the cornersat the corners
Found tightly packed together just Found tightly packed together just below the epidermisbelow the epidermis
Collenchyma CellsCollenchyma Cells
Longitudinal view
Cross sectionshowingunevenwall thickening
SclerenchymaSclerenchyma
Two cell typesTwo cell types• fibers fibers • sclereids. sclereids.
Non-living at maturityNon-living at maturity Thickened secondary wallsThickened secondary walls
FibersFibers
Elongate cellsElongate cells Function in supportFunction in support Leaf and stem fibers from many plants Leaf and stem fibers from many plants
used for cloth and rope. used for cloth and rope.
Sclereids Sclereids
Various shapesVarious shapes FunctionsFunctions• mechanical support and mechanical support and • protectionprotection
Account for the hardness in nut shells Account for the hardness in nut shells and the grit of pear fruitand the grit of pear fruit
SclerenchymaSclerenchymaX-section of fiber showingthick secondary wall
Fiber
Sclereid x-sectionshowingthicksecondarywall
Sclereids
SclereidsSclereids
Vascular tissues Vascular tissues
XylemXylem - - conducts water and minerals conducts water and minerals from the roots upwardfrom the roots upward
PhloemPhloem - transports organic materials - transports organic materials (sugars) synthesized by the plant(sugars) synthesized by the plant
XylemXylem
Cells conducting water - non-living Cells conducting water - non-living • TracheidsTracheids - long thin cells with tapering - long thin cells with tapering
walls and numerous pits walls and numerous pits • VesselVessel elementselements - short, wide, with - short, wide, with
horizontal end walls with large openings horizontal end walls with large openings • Both cells have secondary walls Both cells have secondary walls
Fibers - non-living - provide supportFibers - non-living - provide support Parenchyma cells - metabolic activity Parenchyma cells - metabolic activity
Tracheids and VesselsTracheids and Vessels
Xylem Cells from Oak WoodXylem Cells from Oak Wood
Primary and Secondary Xylem Primary and Secondary Xylem
Primary xylemPrimary xylem develops from the develops from the apical meristem apical meristem
Secondary xylemSecondary xylem develops from the develops from the vascular cambium. vascular cambium.
In trees secondary xylem is very In trees secondary xylem is very extensiveextensive
PhloemPhloem
Cell Types in phloemCell Types in phloem• Sieve Tube Members - transport sugars Sieve Tube Members - transport sugars • Companion Cells - loading and unloadingCompanion Cells - loading and unloading• Fibers - supportFibers - support• Parenchyma - metabolic activityParenchyma - metabolic activity
Primary and Secondary phloemPrimary and Secondary phloem
Sieve Tube MemberSieve Tube Member
• Living cells with Living cells with only thin primary only thin primary wallswalls
• End walls have End walls have sieve plates (large sieve plates (large pores with large pores with large plasmodesmataplasmodesmata))
End wall with sieveplate
Companion cellsCompanion cells
• Specialized parenchyma cell develops Specialized parenchyma cell develops alongside a sieve tube memberalongside a sieve tube member
• Plasmodesmata connect it to sieve tube Plasmodesmata connect it to sieve tube member member
• Loading and unloading sugars for transportLoading and unloading sugars for transport
Plant Tissues and CellsPlant Tissues and Cells
Tissue TypeTissue Type Cell TypesCell Types FunctionFunction DermalDermal
EpidermisEpidermis epidermal cells epidermal cells protectionprotection Periderm Periderm cork cellscork cells protectionprotection
GroundGround ParenchymaParenchyma parenchyma cells parenchyma cells storage,storage,
photosynthesisphotosynthesis Collenchyma Collenchyma collenchyma cells collenchyma cells supportsupport Sclerenchyma Sclerenchyma sclereids, fibers sclereids, fibers support,support,
protectionprotection
Plant Tissues and CellsPlant Tissues and Cells Tissue TypeTissue Type Cell TypesCell Types FunctionFunction VascularVascular
Xylem Xylem tracheids water tracheids water
vessel elements conductionvessel elements conduction
fibers supportfibers support
parenchyma metabolismparenchyma metabolism
PhloemPhloem sieve tube transport sieve tube transport
member sugarsmember sugars
companion cellscompanion cells loadingloading
fibersfibers supportsupport
parenchyma metabolismparenchyma metabolism
Plant OrgansPlant Organs StemsStems• Support leavesSupport leaves• Conduct water and sugarsConduct water and sugars
RootsRoots• Anchor the plantAnchor the plant• Absorb water and mineralsAbsorb water and minerals
LeavesLeaves• PhotosynthesisPhotosynthesis• TranspirationTranspiration
Herbaceous Dicot StemHerbaceous Dicot Stem
X
P
EpidermisCortex (parenchyma cells)
Pith (parenchyma cells)
Vascular bundle
Cross-section
Monocot StemMonocot StemEpidermis
GroundTissue
Vascular bundle
ScatteredVascular Bundles
RootsRoots
SteleEpidermis
Xylem
Cortex
PhloemEndodermis
root hair
LeafLeaf
X
P
Epidermis
VeinsSpongy mesophyll (parenchyma)
Palisade Mesophyll (parenchyma)
Leaf from LigustrumLeaf from Ligustrum
Secondary Growth in DicotsSecondary Growth in Dicots
5 Year Old Woody Dicot Stem5 Year Old Woody Dicot StemOneannual ring
Periderm (cork)Cortex
Secondary phloem
Vascular Cambium
5 Years of Secondary Xylem
Three Year Old TreeThree Year Old Tree
DendrochronologyDendrochronology
Study of tree rings has added many Study of tree rings has added many fields of studyfields of study
Can tell us about past climatesCan tell us about past climates Can be used to date from archeological Can be used to date from archeological
sites artifacts sites artifacts Tree ring research lab at the University Tree ring research lab at the University
of Arizona of Arizona http://www.http://www.ltrrltrr..arizonaarizona..eduedu//
SummarySummary
Growth, replacement of cells, and Growth, replacement of cells, and asexual reproduction all depend on cell asexual reproduction all depend on cell divisiondivision
Tissues are groups of cells that perform Tissues are groups of cells that perform a common functiona common function
Stems, roots and leaves are made up of Stems, roots and leaves are made up of three basic tissue types: dermal, three basic tissue types: dermal, ground, and vascularground, and vascular