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Stems

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Stems and their Functions

Nodes and Internodes

Support leaves

Produce carbohydrates

Store minerals

Transports water and solutes

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External Structure

Nodes

Internodes

Buds

Leaf Scar

Bundle Scar

Bud Scale Scar Other Scars

Lenticels

Buds Position or Location

Terminal/Apical Lateral/Axillary

 Adventitious Presence or Absence

of protective covering Protected Naked

Structures into whichthey develop Vegetative Flower Mixed

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Source: http://academic.kellogg.edu/herbrandsonc/bio111/stems.htm

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Internal Structure of Stems

Three tissues

Epidermal Tissue

Trichomes

Vascular Tissue

Xylem

Phloem

Ground Tissue Cortex

Pith

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Transverse section of corn stem (Zea mays) 

http://www.sbs.utexas.edu/mauseth/weblab/webchap11stem/11.1-2.htm

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Transverse section of corn stem (Zea mays) 

http://www.sbs.utexas.edu/mauseth/weblab/webchap11stem/11.5-5.htm

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http://people.hsc.edu/faculty-staff/edevlin/edsweb01/new_pa6.jpg

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Herbaceous eudicot stem cross section

http://www.uic.edu/classes/bios/bios100/labs/herbstems.htm

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https://reader009.{domain}/reader009/html5/0325/5ab770f0caabb/5ab770f5d4573.jpg

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Longitudinal section of axillary meristem of coleus (Coleus) 

http://www.sbs.utexas.edu/mauseth/weblab/webchap6apmer/6.1-4.htm

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Secondary Growth

The VascularCambium

Ray initials

Fusiform initials Secondary Xylem

Kinds of Wood

Bark Secondary Phloem

Periderm

Unusual Growth

Eudicots

Monocots

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Secondary Growth

 Absent in all species of modern ferns

Present in gymnosperms

Present in basal angiosperms and eudicots, but

others are herbs Ordinary type is absent in monocots, but some

have anomalous secondary growth

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https://reader009.{domain}/reader009/html5/0325/5ab770f0caabb/5ab770f7bccba.jpg

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http://www.deanza.edu/faculty/mccauley/6a_site_images/tilia-2yr-670.jpg

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https://reader009.{domain}/reader009/html5/0325/5ab770f0caabb/5ab770fc33413.jpg

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https://reader009.{domain}/reader009/html5/0325/5ab770f0caabb/5ab770fd279a2.jpg

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Radial section of pine wood

The latewood tracheids onthe left are such narrow cellsthat their circular borderedpits must be small to fit ontheir small radial walls.

http://www.sbs.utexas.edu/mauseth/weblab/webchap15wood/15.2-12.htm

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Secondary Xylem: Wood

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Kinds of Wood

Softwood

Nonflowering seedplants

Hardwood Eudicots

Sapwood

Water and dissolvednutrients

Heartwood Waste products

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https://reader009.{domain}/reader009/html5/0325/5ab770f0caabb/5ab770ff21028.jpg

https://reader009.{domain}/reader009/html5/0325/5ab770f0caabb/5ab770ff4e5fc.jpg

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http://4.bp.blogspot.com/_lofizJ7zoB8/R9FV3apXYSI/AAAAAAAABg0/DdA7DbIFZeo/s400/cutting-boards_LRG.jpghttp://www.gardentreeslandscape.com/wp-content/uploads/2011/07/Hardwood-Trees.jpg

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http://www.doitpoms.ac.uk/tlplib/wood/figures/tree_trunk_cut_through_sml.png

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Transverse section. of cactus bark (Acanthocereus sicariguensis) 

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Transverse section of ivy stem with lenticel (Hedera helix) 

http://www.sbs.utexas.edu/mauseth/weblab/webchap17bark/17.3-1.htm

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Unusual Secondary Growth

Eudicots Unusual behavior of a

typical vascularcambium (Daucus) 

Presence of morethan one cambium(Beta vulgaris)

Differential activity of a

vascular cambium( Aristolochia) 

Monocots Dracaena and

Cordyline

Form a vascularcambium just outsidetheir vascular bundles

Monocot cambium

Only one irregularly

shaped type of cell

Parenchymatoussecondary cortex andlignified conjunctivetissue

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The stem of Beta vulgaris  containssome vascular bundles embeddedin a pith-like parenchymatous core,and immediately exarch of this, is abroad band of tissue which is entirelysecondary, which includes acambial zone (CZ).

This micrograph shows one of theprimary bundles, which occur towardsthe center of the beetroot stem, indetail. Note that this vascular bundleis inverted.

http://anubis.ru.ac.za/Main/ANATOMY/betast3.jpghttp://anubis.ru.ac.za/Main/ANATOMY/ANOMALOUS/beta5.jpg

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 Arborescent monocotyledons. (A) Dracaena draco, (B) Dracaena yuccaeifolia, (C) Yucca sp.,

(D) Pandanus sp

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Uses of Secondary Xylem and Phloem

Lumber Pulp and Paper Fuel Charcoal and Related Products Fabrics and Rope Sugar and Spice Dyes Drugs Other Uses

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Modified Stems

Modified Stems thatGrow Aboveground

Stolons or runners

Tendrils and twiningshoots

Searcher shoots

Cladodes orcladophylls

Thorns

Short and long shoots

Succulent stems

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Examples of different kinds of modified stems

http://www.cfwep.org/education/smsp/module07/m0707-content-psstemvt.html

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(A & B) stem tendrils; (C, F, andG) thorns; (D & E) leaf-like stems

http://www.biog1105-1106.org/demos/105/unit4/plant.anatomy.html

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http://www.tutornext.com/system/files/u77/Image_1.GIF

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http://www.preservedgardens.com/images/pressed-foliage/virginia_creeper.jpg

http://3.bp.blogspot.com/_Z_WFblZncWM/TCfvLey8_fI/AAAAAAAAADA/L8BuLYtMZNQ/s1600/Lonicera+morrowi.jpg

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Cladodes of Asparagus sp., resembling leaves

http://www.sci.sdsu.edu/plants/plantsystematics/morph/vegetative/cladode-Asparagus.jpg

Epidendrum ciliare

http://www.orchidflowerhq.com/orchidpictures/Epidendrum-orchid.jpg

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http://www2.puc.edu/Faculty/Gilbert_Muth/art0042.jpg

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https://reader009.{domain}/reader009/html5/0325/5ab770f0caabb/5ab771085cf0d.jpgB. trifoliolata long shoot arising from short shootas the result of damage to the original longshoot apex

http://w3.biosci.utexas.edu/prc/DigFlora/BERB/images/BETR-4Jul-SS2LS.JPG

M difi d St

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Modified Stems

Modified Stems thatGrow Belowground

Bulbs

Rhizomes

Corms

Tubers

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http://www.cobalt-group.com/frontpagewebs/Content/Classify/classifi.htm

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http://www.littleexplorers.com/subjects/plants/gifs/Bulb_bw.GIF

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https://reader009.{domain}/reader009/html5/0325/5ab770f0caabb/5ab7710a904a5.jpg