wonderful world of stems. stinging hairs urtica dioica
TRANSCRIPT
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