Chapter 9 Mind Map
Concepts
Vascular Cambium
Secondary Xylem
Secondary Phloem
Outer Bark
Secondary Growth in Roots
Anomalous Forms of Growth
tissues derived from meristem
epidermis
cortex
vascular bundles
pith
leaves
primary tissues (listed above)
constitute the primary plant body
can be only plant body that develops (herbs)
can be base for secondary tissues (woody species)
secondary tissues
tissues are wood
constitute the plant's secondary body
examples include trees (pines) and shrubs (roses)
bark/wood
trees gain more and more over time
contain conducting tissues (phloem and xylem)
photosynthetic capacity increases as bark increases
initiation of the vascular cambium
fusiform initials
ray initials
arrangement of cambium cells
vascular cambium
one of the meristems that produces the second plant body
cells between metaxylem and metaphloem don't stop dividing
cells are called fascicular cambium
fascicular cambium
cells are located between metaxylem and metaphloem
continue to divide (in primary plants this division would stop)
interfascicular cambium
some mature parenchyma cells can come out of cell arrest
cells resume division
connects with fascicular cambium on both sides
terms fascicular and interfascicular can only be used for 2-3 years
long, tapered cells
vascular cambium has two parts
fusiform initials
ray initials
typically undergo longitudinal cell division
periclinal wall forms for longitudinal division (parallel wall)
one resulting cell remains fusiform, the other differentiates
occasionally, vascular cambium will divide longitudinally
anticlinal wall forms (perpendicular wall)
similar to fusiform initials
shorter and more cuboidal
also undergo periclinal division
provide mostly storage parenchyma
ray and fusiform initials are organized in specific patterns
ray initial organization
short vertical rows
can be one cell wide (uniseriate)
can be two cells wide (biseriate)
can be many cells wide (multiseriate)
may occur in
regular horizontal rows (stored cambium)
irregular horizontal rows (nonstoried cambium)
if multiple columns of fusiform initials are found, ray initials will form in the middle
the same thing will occur if multiple columns of fusiform initials are found
types of wood cells
secondary xylem
growth rings
heartwood and sapwood
reaction wood
also known as wood
all cells formed to the interior of the vascular cambium
arrangement of secondary xylem reflects initials
axial system is derived from fusiform initials
radial system is derived from ray initials
angiosperm woods / hardwoods
commercially important
wood of all basal angiosperms and eudicots
contain large amounts of fibers
strong, tough, and useful for construction
softwoods
few or no fibers
can be much harder than hardwoods
trees such as pines and redwoods
rays
uniseriate, biseriate, or multiseriate masses
arrangements of parenchyma in woody angiosperms
two types of ray parenchyma cells
upright cells
procumbent cells
ray tracheids
horizontal, rectangular cells
look like parenchyma that have secondary walls
also have circular bordered pits and protoplasts
early wood
also called spring wood
first wood formed
has a high proportion of wide vessels/tracheids
late wood
also called summer wood
has a lower proportion of vessels
contains more numerous fibers/tracheids
transpiration is lessened and cuticle is thickened
annual ring
one year of growth
consists on early and late wood combined
trees may fail to form ring due to cold temperatures
sometimes called growth ring
diffuse porous
growth ring has vessels scattered throughout
examples are yellow birch, aspen, and sugar maple
ring porous
vessels are mainly restricted to early wood
example are red oak, sassafras, and honey locust
heartwood
inner portion of log
drier, more fragrant, and darker
sapwood
outer portion of log
moister and lighter
tylosis
plug formed of protoplasm
occurs in the pits of parenchyma cells
produced in response to stress
develops mostly on the upper side of branches
also called tension wood
formed from vascular cambium
has an axial and radial system
axial system
responsible for conduction up and down the stem or root
contains sieve tube member and companion cells in angiosperms
contains sieve cells in conifers
size, shape, and number of phloem and xylem rays are identical
cork and cork cambium
lenticels and oxygen diffusion
cork cambium
also called phellogen
formed from the reactivation of parenchyma cells
occurs in secondary phloem
all cells are cuboidal
after each division, inner cell remains cork but outer cell becomes cork cell (phloem cell)
may occasionally produce phelloderm
cork cambium, cork cells, and phelloderm make up the periderm
all tissues of the innermost cork cambium comprise the outer bark
all secondary phloem between vascular cambium and outer bark is the inner bark
mature cork cells are round and form spaces for oxygen diffusion
regions of aerenchymatous cork are called lenticels
multiple regions of lenticels allow for the diffusion of oxygen
lenticels contain more layers of cells and protrude outward
initiation of cork cambia
timing of initiation of the first cork cambium is variable
cork cambium may begin forming as early as 1 year old
first cork cambium arises in the cortex
cork cambia and second phloem create outer bark
roots undergo secondary growth similar to stems
secondary vascular cambium arises between primary xylem and primary phloem
new vascular cambium has star shape in beginning
vascular cambium becomes round with development of secondary xylem
some portions of cambium are pushed outward more rapidly
once cambium is circular, unequal growth stops
conductivity of woody roots is different to woody stems
perennial roots also form bark
first cork cambium arises in the pericycle
endodermis, cortex, and epidermis is shed
cork cambium produces protective layer
phelloderm and lenticels are also formed
anomalous secondary growth
unusual primary growth
alternative cambia produce secondary bodies that differ from the common type
different secondary body growth is called anomalous secondary growth
roots of sweet potatoes
storage parenchyma is increased dramatically
numerous vascular cambia arise
xylem and phloem are made mainly of parenchyma
secondary tissues are made of
parenchyma
sieve tubes
some vessels
vascular cambia
multiple cambia can increase storage capacity
included phloem
in several eudicots, ordinary secondary xylem and phloem are produced
after short period, cambium cells stop dividing
cambium cells then differentiate into xylem
oldest secondary phloem then become reactivated
these cells become new cambium
this process continues over and over again
included phloem
secondary phloem
located in-between bands of xylem
unequal activity of the vascular cambium
in some species, vascular cambium has unequal activity
some areas of the cambium are very active while others are mostly inactive
stem becomes a thin, flat, woody ribbon
stem is extremely flexible
secondary growth in monocots
no monocots have secondary growth
some monocots can become woody
in these, vascular cambium arises just outside of outermost vascular bundles
cambium produces only parenchyma
this parenchyma differentiates into secondary vascular bundles
become "woody" because of fibers
palm tree is made entirely of primary tissues
vascular bundles in primary tissues contains
primary xylem
primary phloem
vascular cambium never develops
vascular bundles are enclosed in strong, heavy fibers
each roots add extra vascular bundles
establishment growth
form of primary growth
increase in width and addition of advantageous roots
Secondary Growth in Roots
Vascular Cambium Development
Secondary Tissue Growth and Description
Secondary Phloem in Roots
click to edit
Cork Cambium