Wonderful World of Stems Stinging Hairs Urtica dioica

Wonderful World of Stems

Stinging Hairs Urtica dioica

Dendrocnide excelsa Australian Stinging Tree, Dendrocnide excelsa

Dicot vs. Monocot Stems

Fibers (sclerenchyma)

Vascular Bundles C. s. of a dicot vascular bundle

Fibers for Stem Strength

Vascular Cambium

Secondary Xylem Vascular Cambium Secondary Phloem

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

Phellum (cork) (dead) Cork cambium Phelloderm (living) • Epidermis fracturing, with periderm below

• Old periderm often called, “outer bark”

Pine bark Eucalyptus bark

Lenticels

Girdling

Softwood

Hardwood

Heartwood (inactive) Sapwood (active)

Transverse = cross section Radial + Tangential = longitudinal sections

Wood Knots

Wood grain

Wood Density Guaiacum officinale

Some plants grow tall without secondary growth:

Rhizome Stem types Bulb Corm Stolon

Stem Types Cladode Tuber Tendril