Wonderful World of Stems

Stinging Hairs

Urtica dioica

Dendrocnide excelsa

Australian Stinging Tree, Dendrocnide excelsa

Dicot vs. Monocot Stems

Fibers (sclerenchyma)

C.s. of a dicotvascular bundle

Vascular Bundles

Fibers for Stem Strength

Vascular Cambium

SecondaryXylem

SecondaryPhloem

VascularCambium

Axial and ray systems

Annual growth rings

•Early wood larger cells•Spring wood

•Late wood smaller cells•Summer wood

Bristlecone Pine

•Dendrochronology dated one at 5,000 years old(and counting!)

1,000 growth rings packed into just 13 cm. of wood

Sequoia semperivirens

•Tallest living organism (112 m.) – the ‘Mendocino Tree’•Weighs 1,600 tons (or 10 blue whales)•Roots only 1.8 m. deep!•Average Sequoia uses 1,100 L of water per day

Castanea

World’s fattest tree at 58 m. diam., found on Mt. Etna, Italy, the “Tree of One Hundred Horses”

Secondary growth - bark

•Epidermis fracturing, with periderm below

Cork cambium

Phellum (cork)(dead)

Phelloderm(living)

•Old periderm often called, “outer bark”

Pine bark

Eucalyptus bark

Lenticels

Girdling

Softwood

Hardwood

Heartwood(inactive)

Sapwood(active)

Transverse = cross sectionRadial + Tangential = longitudinal sections

Wood Knots

Wood grain

Wood Density

Guaiacum officinale

Some plants grow tall without secondary growth:

Stem types StolonRhizome

Bulb

Corm

Stem Types

TuberTendril

Cladode