Leaf anatomy
Leaf anatomy
• Leaves start as
outgrowths
from apical
meristem: leaf
primordia.
Leaf anatomy
• 3 primary
meristems
– protoderm:
becomes
__________
– procambium:
becomes
___________
– ground
meristem:
becomes
____________.
• Epidermis:
note cuticle,
stomata
• Veins with
vascular
tissues
(__________
• __________)
• Supply water
& nutrients,
remove sugars
for transport
elsewhere.
Leaf anatomy
Leaf anatomy
• Mesophyll
– Parenchyma
tissue layers
(palisade and
spongy: do
____________.
Monocot vs dicot anatomy
• Stem: Dicot with bundles __________. Pith
and cortex present.
• Monocot: scattered vascular bundles. No
_______________.
Monocot vs dicot anatomy
• Root: Dicot, < 6 phloem patches, no pith
Monocot vs dicot anatomy
• Root: Monocot, many _____________, pith
present
Monocot vs dicot summary
• Note root system type: dicot often with single
major root axis (taproot system), monocot
lacking this (fibrous root system)
Plant Growth Phenomena
• Hormones: molecules produced in small
amounts that change _________________
• _________
• Can inhibit or stimulate processes to occur
• 5 major types:
–
–
–
–
–
auxins
cytokinins
gibberellins
ethylene
abscisic acid
Auxins
• Promote stem
elongation and growth
• Example,
___________.
Bending of stem
toward light
Auxins
• Also involved in ______________: suppression
of lateral meristems by apical meristem
Auxins
• Can stimulate production of
______________ roots (roots
produced on stem or leaf)
• Useful in rooting cuttings
(asexual plant reproduction)
Cytokinins
• Stimulate cell division where auxin is
also present
• Acts as ____________ hormone (keeps
detached leaves green).
Gibberellins
• Promote stem elongation
• Mutant plants with low amounts are _________
(internode lengths short)
Ethylene
• Promotes fruit ripening
• Stimulates ____________ (dropping) of leaves,
flowers
Abscisic acid
• Induces formation of
winter buds (bud
scales, dormant
meristem)
• Involved in opening
and closing of
_____________
• Can cause seed
dormancy
Other plant growth phenomena
• Gravitropism:
response of stem/root
to gravity
• Stems bend away
from gravity
(___________
gravitropism)
• Roots bend toward
gravity (_________
gravitropism)
Other plant growth phenomena
• Mechanism
unclear. May
involve ________
________ called
statoliths (in root
cap of root, in
parenchyma cells
of stem)
Other plant growth phenomena
• Thigmotropism: response
of plant to __________
• Examples: Many tendrils
grow toward stimulus and
wrap around object
Turgor movement
• Not growth: involves
loss of water pressure
(turgor pressure) in
some cells
• Can be reversed
• May involve rapid
movement (electrical
signal)
• Ex, sensitive plant
QuickTi me™ a nd a Cinep ak decompre ssor are n eede d to see thi s pi ctu re.
Flowering
• Some plants use daylength as
flowering cue
• Can measure length of night
(photoperiod) by pigment
called ______________
• Long day plants:
flower when night
is ________ than
some critical time
• Short day plants:
flower when night
is _______ than
some critical time
• Day neutral
plants: don’t use
photoperiod as
flowering cue
Flowering
Flowering
• Use: Can make some plants bloom when we
want them
• Ex, poinsettia. A short-day plant that growers
make flower for Christmas holidays.
Plant transport
• Phloem: sugars and water (often from leaf to root)
• Xylem: water and minerals from root to shoot
• Movement driven by _____________: measure of
tendency of water to move from one place to
another
Plant transport
• Water potential is affected by:
– solutes (high solutes = ______ tendency to move)
– pressure (high pressure = ______ tendency to move)
– tension (pull: high tension = ______ tendency to move).
Water transport
• Xylem: water and minerals from root to shoot
• How much of water remains in plant? <____%!
Water transport
• Transpiration: evaporation of water from leaves
• Driven by _______ from leaves. Water under
tension. Water potential high in soil and low in
air.
Water transport
• Driven by pull
from leaves.
Water under
tension. Water
potential high in
soil and low in
air.
Water transport
• Transpiration greatly controlled by stomata
• Stomata open in ________ but can close if plant
lacks sufficient water.
Stomata!
Sugar transport
• Phloem: sugars and water
• Flow from ______ to _____
• Pressure flow mechanism
Sugar transport
• Source: lots of sugar
dissolved in water.
Generates pressure as
water flows in to
_______ sugar
• Sink: little sugar
dissolved in water. Low
pressure as water flows
out
• Creates ___________
gradient that moves
fluid thru sieve tubes.
Sugar transport
• Result: sugar flows to
wherever demand is
high
Secondary Growth
Secondary Growth
• Two types of growth
• Primary growth: up and
down. Generated by apical
meristems. Form _________
tissues
• Secondary growth: growth in
girth. Generated by lateral
(secondary meristems). Form
__________ tissues.
• All plants do primary growth
• Woody plants do __________
growth
Secondary Growth
• Lateral meristems
– 1) ______________: makes
new phloem and xylem
– Called ________ phloem and
xylem tissues (vs. primary
phloem and xylem made
directly from procambium)
– Function: xylem takes water
+ minerals to leaves, phloem
takes sugars to roots
Secondary Growth
• Lateral meristems
– 2) ___________: makes new
cell type, cork cell. Cork cells
with primary wall
impregnated with waxy
material (_______). Dead at
maturity. Forms waterproof
layer on outside of body to
replace epidermis.
– _________: Tissue composed
of cork cells and made by
cork cambium. Also is a
secondary tissue.
Secondary Growth
• Stem cross section
Secondary Growth
• Vascular bundles contain __________________
• Located between primary xylem and phloem
• Meristematic: can still do _______________
Secondary Growth
• Residual procambium cells start to divide
• Produce new cells ______________
Secondary Growth
• Parenchyma cells between bundles also start to divide
• Together form solid ring of cells, all dividing laterally
• This is __________________
Secondary Growth
• Vascular cambium makes secondary xylem on
__________, secondary phloem on __________
• Note how cambium moves outward over time
Secondary Growth
• Note arrangement of primary phloem and secondary
phloem, primary xylem and secondary xylem
Secondary Growth
• Secondary xylem may contain:
–
–
–
–
1) Vessel elements
2) Tracheids
3) ____________
4) Fibers
• Secondary phloem may contain:
–
–
–
–
1) Sieve tube elements
2) Companion cells
3) Parenchyma
4) ___________
Secondary Growth
• Two
Secondary Growth
• Later secondary growth
Secondary Growth
• First cork cambium: Forms under ___________
Secondary Growth
• Cork cambium: Makes files of cork cells to
outside. Forms first __________. Epidermis
cut off from rest of stem and dies.
Secondary Growth
• Problem: cork cells are
dead at maturity. Cork
layer cannot _________ as
vascular cambium
continues to grow.
• Solution: form new ______
______ in cortex under old
one
• After time, several
__________ build up
(yellow lines). Newest
(inner) one cuts off water
to layers beyond it and they
_______.
Secondary Growth
• Periderm replaces epidermis. How get _______
into stem?
Secondary Growth
• Lenticels: Loosely packed __________. Allow
oxygen to diffuse into stem to support living
cells there.
Secondary Growth
• Note ____ made by
vascular cambium:
Form ________
transport system
(often parenchyma
cells)
• In phloem: phloem
ray
• In xylem: xylem
ray (wood ray)
Secondary Growth
• In temperate zone, cambium activity varies
between _____ and ______ in growing season
• Spring: big cells (_______ wood).
• Summer: small cells (_______ wood).
• Form growth ring (tree ring): one season’s growth
• Ex, pine (mostly tracheids)
Secondary Growth
• Ex, oak (note vessels, thick-walled _________)
Secondary Growth
• Young tree section: Note rays here (phloem and
xylem)
• Also note growth rings: early and late wood
• How old was this stem when cut?
Secondary Growth
• In older tree: wood
is secondary xylem
• Heartwood: old
non-functional
xylem
• ________: younger
often functional
xylem
Secondary Growth
• Bark: From vascular
cambium outward
• ___________: From
current cork
cambium outward
(all is dead)
• __________: From
vascular cambium to
current cork
cambium. Contains
functional secondary
phloem
Secondary Growth
• Removing inner bark
is deadly: girdling
tree often will kill it
• Why? Roots ______
• Why? No ________
from leaves.
Secondary Growth
• Flow chart, showing how primary and
secondary tissues develop in stem
Secondary Growth
• Note that roots of woody plants also do secondary
growth
• Vascular cambium forms from __________
• First cork cambium forms in _____________.
Secondary Growth
• So outer cortex and epidermis are sloughed off
and lost
Uses of Growth Rings
• 1) Fire frequency
• Break in bark (_________)
allows fire to burn through
vascular cambium into
wood
• Leaves burned layer
• If tree survives, can have
record of fires in wood.
Ponderosa pine, WY
Uses of Growth Rings
• 1) Fire frequency
• Helpful information
when trying to
determine “natural”
frequency of fires for
managing forests.
Uses of Growth Rings
• 2) Climate patterns (___________________)
• Width of rings can indicate growth conditions
for tree (rainfall, etc.)
• Can reconstruct climate information
• Oldest reconstructions go back 8,000 yr B.C.
Uses of Growth Rings
• 2) Climate patterns
• Oldest
reconstructions from
bristlecone pine
wood go back as far
as ________ yr B.C.