Botany Unit 2 Wood and Bark

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wood
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Terms in this set (27)
wood
secondary xylem
wood functions
conduct water
storage
water
carbohydrates
support in trees
vascular cambium
adds secondary xylem and phloem
cell types
fusiform initials
ray initials
fusiform initials
tapered
rectangle
produce axial system
fusiform initials in xylem
gives rise to
vessel elements
tracheids
axial parenchyma
fibers
fusiform initials in phloem
gives rise to
sieve tube elements
axial parenchyma
companion cells
fibers
ray initials
round cells
gives rise to rays in
xylem
phloem
axial system
cells with vertical axes
originate from the fusiform initials
includes the bulk of the wood
vessel elements
tracheids
fibers
axial parenchyma
radial system
consists of the rays
composed of ray parenchyma cells with horizontal axes
originate from the ray initials
function
allow for horizontal movement of food and water
store water, starch, lipids, etc.
gymnosperm wood
conifers, pine trees, fir trees, etc.
simple axial system
tracheids with prominent bordered pits
frequent resin ducts
lack vessels
angiosperm woodflowering plant trees and shrubs complex axial system vessel elements tracheids fibers axial parenchymagrowth ringsform in trees of temperate regions due to water availibilityearly (spring) woodwater abundant vessels numerous and wide in diameterlate (summer) woodwater less abundant vessels less numerous and narrow in diametersapwoodfunctional xylem that is actively conducting water problem non-conducting xylem serves as a route for fungal and bacterial diseasesheartwoodnon-functional wood that has ceased conducting need to be sealed off to prevent infections tyloses gummosis may store waste products these changes cause the wood to change colortylosesparenchyma cells next to a vessel element grows through pits backs up the old vessel elementgummosisparenchyma next to vessel element secrete gummy substances into the vesselbarksecondary phloem and periderm replaces epidermis takes over functions of epidermis protection gas exchangeouter barkperiderm dead tissuesinner barkphloem living tissueperidermsecondary tissue that replaces the cortex and epidermis multiple layers of periderm each layer formed by a phellogen layer only innermost layer is livingphellogenmeristematic layer derivatives produce phellem layers (cork cambium)phellemdead and suberized (cork cells)lenticelarea of bark surface with loosely packed spongy cells large intercellular spaceslenticel functionallow gas to enter the outer bark circulate to inner barkphellodermtissue formed inwardly by the cork cambium inner part of the periderm