What is secondary growth? Growth in girth of woody plants
Tissues derived from cambial layers VASCULAR CAMBIUM produces
secondary xylem and secondary phloem CORK CAMBIUM (phellogen)
produces cork (phellem) and phelloderm tissues
Secondary Xylem (up close and personal) Fibers Tracheids
Vessels Ray parenchyma
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Growth Rings Spring (Early) Wood first cells produced by the
vascular cambium large cells (good growing conditions) Summer
(Late) Wood smaller cells produced toward the end of the growing
season poor conditions (cooler, drier) Radical change in cell size
allows for recognition of annual growth rings
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Bristlecone Pine (oldest of tree species in North America) 4900
+ years old
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Oak Wood in Section Note: thick, multiseriate wood rays
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Other Variations Heartwood darker in color occupies center of
the stem, more dense (stronger) deposit of waste products such as
resins, gums, oils, and tannins Sapwood lighter in color outer
layers, less dense (weaker) contains the sap (dissolved nutrients
and water)
Lenticels Pores in the cork layers which allow for gas exchange
in the periderm
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Uses of Secondary Growth Wood Products Various uses based on
the density of the wood (often in lbs./cubic foot) Furniture,
baseball bats, plywood, pulp products, musical instruments,
particle board, artistic pieces, fuel Other Products rope,
cinnamon, dyes, drugs (quinine), charcoal, cork, maple syrup
Slide 17
Cork Harvesting
Slide 18
Making Maple Syrup 30-50 gallons of sap to make 1 gallon of
syrup