2* Growth Flashcards
1* growth =
axial lengthening
2* growth =
lateral widening
most stems with 2* growth have a
eustele
vascular cambium produces
2* X (wood) & 2* P (inner bark)
vascular cambium forms from
fascicular cambium (in the bundles) & the interfascicular cambium
interfascicular cambium forms from
1* ray (parenchyma)
fascicular cambium froms from
procambium
fascicular cambium location
in vascular bundles
in the pith ray…
…parenchyma despecializes & becomes meristematic
vascular cambium is a type of
lateral mersitem (usually for the life of the organ)
axial region function =
transport along the organ
radial region has
rays
rays function =
radial transport & storage
in between rays =
axial regions
rays continue into
2* P
pine wood axial regions =
ONLY tracheids (no vessels)
pine wood rays are made up of (2)
parenchyma & short tracheids
pine wood rays are…
…uniseriate = 1 cell thick
pine wood has large
resin ducts that look like vessels but ARE NOT VESSELS
pine wood smaller diameter xylem cells helps
prevent cavitation (emboli)
narrow xylem cells =
late wood (preparing for winter / low nutrient season)
thick xylem cells =
early wood (spring / high nutrient season)
pine wood tracheids have
bordered pits
bordered pits of conifers have
margo & torus (most others don’t)
pine/conifer/redwood wood =
soft wood
soft wood =
wood without fibers
bordered pit function
when negative pressure from air bubble (emboli) tries to enter another cell, pits have margo membrane (with thin microfibrils) and torus (middle) that block pits from air bubble entering
margo and torus to limit
the spread of emboli
2 types of flowering plant wood:
ring-porous
diffuse-porous
ring porous wood only occurs in
plants with vessels (usually flowering plants)
different sized larger “pores” in ring-porous wood =
vessels
ring porous wood early wood vs late wood:
- early: huge vessels / thick fiber cw’s (hard)
- late: big vessels / thin fiber cw’s (softer)
early wood huge vessels means
higher chance of embolism
in angiosperms (flowering plants), most cells in axial regions =
fibers (for support)
in angiosperms, rays can be
multiseriate = >1 cell thick
in angiosperms, all ray cells are
parenchyma
diffuse porous wood examples
cottonwood, willows, tropical rainforest
ring porous wood example
oak
diffuse porous wood vessel sizes
are all about the same
diffuse porous wood fiber cw’s & diameter
thickness changes with season
diffuse porous wood vessels have
simple perforation plates on vessel elements
diffuse porous wood majority of axial regions (longitudinal/radial) =
& radial regions =
fibers
& rays
if all cells in the axial regions look the same =
pine/non-flowering wood
2* phloem has same cells as
those in 1* phloem
pine 2* P have
2* sieve cells in cw
pine 2* P wood axial cells =
tracheids
pine 2* P young stem shows
old cortex still
pine 2* P radial regions =
ray parenchyma
angiosperm 2* P have
STM + companion cells
what is lost in 2* growth?
older bark (including 2* P)
2* X vs 2* P growth amount ratio =
10 : 1
10 wood cells : 1 inner bark cell
periderm function
replaces epidermis
periderm is found in
woody plants
periderm formation:
cork cambium (phellogen) initiates just inside epidermis
cork cells are
dead at maturity
cork cw’s have
suberin
cork parenchyma aka
can be
phelloderm
photosynthetic
cork parenchyma function
storage & photosynthesis
cork cambium is often
bifacial
cork cambium separates
cork (outside) & cork parenchyma (inside)
mature periderm exhibits?
& especially where?
proliferation (rapid growth)
especially in cork cells
mature periderm have
lenticels = openings in the periderm that allow for diffusion of gases in & out of stems)
