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CHAPTER 8: STRUCTURE OF WOODY PLANTS, bark - Edited - Coggle Diagram
CHAPTER 8: STRUCTURE OF WOODY PLANTS
Concepts
Primary Growth
apical meristems
primary tissues
herbaceous plants
taller
(mostly) set vascular capacity
Secondary Growth
vascular cambium
#
secondary tissues
woody plants
cork cambium
#
wider
wood
secondary xylem
bark
#
#
secondary phloem
increasing vascular capacity
Wood in Three Dimensions
sections
Radial section
Tangential section
Transverse (cross) section
pine wood contains only tracheids
oak wood has vessels
Secondary Growth in Roots
roots of conifers and woody angiosperms
vascular cambium
like interfascicular cambium
parenchyma and pericycle cells
starts star-shaped
becomes circular
ray and fusiform initials
sapwood and heartwood
ring porous or diffuse porous
root wood and stem wood similar but not identical
perennial roots
first bark arises in pericycle
endodermis, cortex, and epidermis shed
axial and radial systems
carrots and other root vegetables
wood parenchyma
Having Multiple Bodies in One Lifetime
woody plants
primary and secondary
very different
second grows inside of and destroys part of first
animals
puberty
humans
(also teeth)
eels
molting
exoskeleton
crabs
lobsters
beetles
skin
snakes
metamorphosis
caterpillars
butterflies
moths
maggots
flies
Outer Bark
Cork and the Cork Cambium
circumferential stretching
new cambium
cork cambium
phellogen
cuboidal cells
periclinal divisions
inner cell
remains cork cambium
outer cell
cork cell (phellem)
sometimes produces inside layer of parenchyma
phelloderm
phellogen + phellem + phelloderm = periderm
maturation
encrust with suberin
waterproof and chemically inert
cell death
nothing digestible or nutritious left
some cells convert to sclereids
periderm stretches
cork cells cannot expand much
every few years, new phellogen must be produced
several layers of cork build up
inner and outer bark
outer bark
outside innermost cork cambium
inner bark
secondary phloem between vascular cambium and innermost cork cambium
Lenticels and Oxygen Diffusion
impermeable cork
blocks absorption of Oxygen
interferes with respiration
rounded cork cells
intercellular spaces
diffusion pathway
aerenchymatous cork
lenticels
protrude outward
Initiation of Cork Cambia
first cork cambium arises
stems
color changes from green to tan
first bark
arises in epidermis
contains periderm, and cuticle
very smooth
arises in cortex
contains periderm, cortex, and epidermis
smooth
later bark
arises in scondary phloem
only cork and phloem
Vascular Cambium
Fusiform Initials
parallel wall cell division
periclinal wall
cambium cell
fusiform initial
vascular cell
inner cell
secondary xylem
wood
increase greatly in diameter
pushes cambium outwards
outer cell
secondary phloem
bark
perpendicular wall cell division
anticlinal wall
increases number of cambial cells
increases circumference
of cambium
necessary because xylem pushes out
#
long, tapered cells
Ray Initials
short and cuboidal cells
periclinal cell division
cambial ray initial
vascular cell
xylem parenchyma
phloem parenchyma
produce short cells
storage parenchyma
Initiation of the Vascular Cambium
fascicular cambium
between metaxylem and metaphloem
interfascicular cambium
between vascular bundles
types of cells
fusiform initials
#
ray initials
#
extended each year
Arrangement
of Cambial Cells
ray initials
short verical rows
width
uniseriate
biseriate
multiseriate
fusiform initials
regular horizontal rows
storied cambium
shorter fusiform initials
irregular; no horizontal pattern
nonstoried cambium
fairly constant distribution of ray and fusiform initials
Thinking about the Growth of Wood
plants have localized growth
hair, nails, and skin too
Secondary Xylem (Wood)
Growth Rings
strongly seasonal climates
classic arrangement
early wood
high proportion of wide vessels
or wide tracheids in conifers
high capacity for conduction
late wood
lower proportion of vessels
more mechanical strength
numerous fibers
narrow thick-walled tracheids in conifers
cambium starts dormant
cambium becomes dormant again
annual ring
growth ring
alternate arrangement
vessels form throughout growing season
diffuse porous
vessels restricted mainly to early wood
ring porous
growth rings are indistinct
Heartwood and Sapwood
heartwood
center
darker
drier
more fragrant
sapwood
moister
outer
lighter
water columns break
cannot conduct water
plug
tylosis
decay-resistant heartwood
new layer of sapwood each year
one ring converted to heartwood each year
Types of Wood Cells
tracheids, vessels elements, fibers, sclereids, parenchyma
axial system
derived from fusiform initials
contains tracheary elements
longitudinal conduction of water
fibers
large amount of fibers
hardwoods
basal angiosperms and eudicots
little or no fibers
softwoods
conifers
columns of xylem parenchyma
temporary reservoir of water
radial system
derived from ray initials
woody angiosperms
only parenchyma
rays
functions
conduct material radially over short distances
store carbohydrates during dormant periods
types of ray cells
upright cells
adjacent to axial parenchyma
1 more item...
adjacent to axial tracheid or vessel element
2 more items...
stored starch first to be digested
procumbant cells
no direct connection with axial cells
stored starch not digested until later
conifers
almost exclusive uniseriate
ray parenchyma
ray tracheids
horizontal, rectangular cells
secondary cell walls
circular bordered pits
protoplasts
Reaction Wood
counteracts stress from gravity on lateral branches
angiosperms
upper side of branch
tension wood
fibers exert tension on branch
prevent from drooping
may contract
lifting branch to vertical orientation
Conifers
underside of branch
compression wood
Secondary Phloem (Bark)
#
axial system
conduction up and down stem or root
angiosperms
sieve tube members
companion cells
fibers and nonconducting parenchyma
conifers
sieve cells
fibers and nonconducting parenchyma
radial system
size, shape, and number of rays matches xylem rays
produced by the same ray initals
parenchyma cells used for storage
Anomalous Forms of Growth
Anomalous Secondary Growth
Roots of Sweet Potatoes
increased storage parenchyma
numerous vascular cambia
around individual vessels or groups of vessels
increases rate of cell production
Included Phloem
several eudicots
short period of normal growth
cambium cells differentiate into xylem
cells in oldest secondary phloem become new vascular cambium
normal growth
cycle repeats
protects phloem from pests
Unequal Activity of the Vascular Cambium
some woody vines
two sectors are very active
two sectors are mostly inactive
thin, flat, woody ribbon
flexibility
Secondary Growth in Monocots
Joshua trees and dragon trees
vascular cambium arises just outside outermost vascular bundles
produces only parenchyma
secondary vascular bundles
Unusual Primary Growth
palm trees
trunks don't taper or branch
no secondary growth
trunk is "woody" due to fibers enclosing vascular bundles
establishment growth
stops at some point
Dendrochronology - Tree Ring Analysis
tree rings
climate
different climates have different growth patterns
wider rings happened in optimal years
age of trees
compare to wood used in buildings, etc
date the buildings, etc.
floating sequence
secondary phloem
bark
secondary xylem
vascular cambium
cork (phellem)
cork cambium (phellogen)
periderm
phelloderm
