Roots, Stems, and Leaves

Life before reproduction

• Reproduction is essential to a species’ success

• Plants have to grow to the point that they are mature enough, and healthy enough, to reproduce.

• Roots, stems, and leaves are the workhorse structures of plants.

Roots

• Obtain water and dissolved nutrients from soil and mycorrhyzae

• Anchor plant• Are point of contact

for mycorrhizal fungi

Types of roots

• Primary root - from embryo

• Secondary roots –from primary root

• Adventitious roots –from leaf nodes– May be modified for

support or defense or …

Aerial root

Adventitous roots

Root structures

• Tap roots – from primary root

• Fibrous roots – from adventitious or secondary roots

• Tuberous roots – thickened ROOTS– Tubers are thickened

stems Stem, not root

Tuberous root

http://www.museums.org.za/bio/images/enb7/enb07429x_beetroot.jpghttp://trc.ucdavis.edu/egsutter/plb171/VisualMaterial/largePhotoSStruc/TubersPic/tuber-potato99lable.jpg

Rhizomes: underground stems, not roots• Rhizomes have nodes and

reduced leaves

• Rhizomes often root at nodes

• Rhizomes enable a plant to spread and reproduce

• Rhizomes are most common in mesic and wet habitats

Stems

• Hold up above ground parts of plant; transmit signals

• Have leaves and may have branches

• Woody or herbaceous• Leaves and branches may be

– Opposite– Alternate– Whorled (Verticillate)

• May have hairs, prickles, thorns, spines

Prickles

AlternateSpines

Caudex (pl.: caudices)

• Woody stem that does not or only scarcely extends above ground

Woody stems also have …

• Lenticels • Leaf scars• Bark

http://www.science.siu.edu/plant-biology/PLB304/TwigPics/AcerSaccharinum.jpg

http://www.virtualherbarium.org/treepuzzle/chars/LENTICELS_ABUNDANCE.html

http://home.tiscali.nl/picturesandadicons/dtp/1024x768dtp3/Bark.jpg

Leaves – absolutely vital

• Evaporation surface (essential to nutrient transport)

• Energy converters– Absorb sunlight– Take in CO2 from air– Release O2 as by-

product

• Food and shelter for others

http://www.huntington.org/BotanicalDiv/TitanPix/leaves.jpg

Leaf structure

• Simple– Lobed, Divided,

pinnatifid, palmatifid, pedate, cleft, parted

http://www.discoverlife.org/nh/tx/Plantae/Dicotyledoneae/Aceraceae/Acer/saccharinum/images/JP80036_61.Simple_leaf_position:Opposite.320.jpg

http://www.esb.utexas.edu/mbierner/bio406d/images/pics/ast/Ambrosia%20psilostachya%20lf2.jpg

Compound

• Palmately• Pinnately

– Odd pin

– Even pinnate

Flat, revolute, involute

Revolute

Leaf margins

• Entire, Crenate, Dentate, Serrate

• Crispate or undulate• Spinose

Crenate margins

Dentate margins

Serrate margins

Crisped leaf

Undulate leaves

Spinose leaf

Leaf apices

http://www.eeob.iastate.edu/classes/botany306/terminology/vegetative/images/leaves/apices.jpg

Leaf bases and attachment

http://www.inhs.uiuc.edu/~kenr/prairieplant.terminology/leaf_bases1.jpg