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Biology:
life study of
What is Life?
Properties of Life
Cellular Structure: the unit of life, one or many
Metabolism: photosynthesis, respiration, fermentation,
digestion, gas exchange, secretion, excretion, circulation-processing materials and energy
Growth: cell enlargement, cell number
Movement: intracellular, movement, locomotion
Reproduction: avoid extinction at death
Behavior: short term response to stimuli
Evolution: long term adaptation
Organismal Circulation
Unicellular Organisms
Autotrophic Multicellular Organisms
(Heterotrophic Multicellular Organisms)
Cyclosis in Physarum polycephalum, a slime mold
This organism consists of one
very large cytoplasm
(plasmodium) with many nuclei
and food vacuoles in the cytosol
(coenocytic).
Slime molds can weigh up
toward kilogram range and
moves their blob-like mass
around exclusively by cyclosis.
http://botit.botany.wisc.edu/courses/img/Botany_
130/Movies/Slime_mold.mov
The correct taxonomic
Here you can see, in a thin
affiliation is unclear.
region of cytoplasm, that it moves
It has been treated as
along pathways that are river-like
Fungus and Protist.
in appearance.
Further study is needed
to resolve its position.
Transport is NOT always
What is the ATP source?
unidirectional.
Cyclosis: cytoplasmic streaming…intracellular circulation
Chloroplasts and
other organelles
have surface
proteins with
myosin-like
activity.
Elodea canadensis
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Microfilaments of
actin are found
just under cell
http://www.microscopy-uk.org.uk/mag/imgnov00/cycloa3i.avi
membrane. What is the source of ATP?
ATP and
Calcium allow
myosin to slide
along actin
filaments,
resulting in
circulation of
organelles within
the cell.
Can you be more specific?
If light intensity were reduced, what would be
the prediction on rate of cyclosis based on
your hypothesis?
Figure 36-3 Page 793
The shoot organ
system is
photoautotrophic,
taking in CO2 and
releasing O2 in
daylight.
Diffusion is sufficient
to exchange gases.
But solutes need to
be circulated in the
large plant body as
diffusion is too
slow!!
The root organ
system is
chemoheterotrophic,
taking in O2 and
releasing CO2 in the
darkness of the soil
environment.
Node
Internode
Apical bud
Axillary bud
CO2 in and O2 out
Node
Leaves
Branch
O2 in and CO2 out
Stem
Lateral roots
O2 in and CO2 out
Taproot
Figure 36-3 Page 793
The shoot system
produces
carbohydrates (etc.)
by photosynthesis.
These solutes are
transported to the
roots in the phloem
tissue:
Translocation
Node
Internode
Transpiration
Carbohydrate
etc.
Node
Leaves
Branch
Stem
Transpiration
The root system
removes water and
minerals from the soil
environment. These
solutes are
transported to the
shoot in the xylem
tissue:
Apical bud
Axillary bud
Translocation
Lateral roots
Water and
Minerals
Taproot
Figure 36-3 Page 793
Node
Internode
Because these
pathways involve
solutes in water
passing in the
adjacent tissues of a
narrow vascular
bundle, this is a
circulation system!
Apical bud
Axillary bud
Carbohydrate
etc.
Node
Leaves
Branch
Stem
Transpiration
Translocation
Transpiration and
Translocation
Lateral roots
The water is moving
up the xylem, and
down the phloem,
making a full circuit!
Water and
Minerals
Taproot
Figure 36-18 Page 802
Plants occur in two major groups (and some minor ones)
They differ, in part, in their circulation systems:
Cross section of a eudicot stem
Cross section of a monocot stem
Epidermis
Cortex
Pith
Ground tissue
Vascular bundles
Dicots initially have one
ring of vascular bundles
Monocots rapidly develop
multiple, concentric, rings
of vascular bundles
Monocot stem anatomy
Mature Monocot
Young Monocot
vascular bundles
As a monocot plant grows in diameter, new bundles are
added toward the outside for increased circulation to the
larger plant body.
Monocot stem anatomy
Is this slice from a young or a
mature part of the corn stem?
Let’s take a
closer look at the
vascular tissues
©1996 Norton Presentation Maker, W. W. Norton & Company
Monocot stem anatomy: vascular bundle
Translocation
Transpiration
©1996 Norton Presentation Maker, W. W. Norton & Company
Why must xylem do a lot more transport than phloem?
Dicot circulation: stem anatomy
Dicots start with one ring of bundles…
Let’s take a
closer look at the
vascular tissues
©1996 Norton Presentation Maker, W. W. Norton & Company
Dicot stem anatomy: vascular bundle
phloem fibers
Support of Stem
functional phloem
Translocation
vascular cambium
Cell Divison: More
Xylem and Phloem
xylem Transpiration
As a dicot grows, how does
it add vascular capacity to
become a tree?
©1996 Norton Presentation Maker, W. W. Norton & Company
Dicot stem anatomy: vascular cambium adds secondary tissues
epidermis
cortex
1º phloem
2º phloem
cambium
2º xylem
1º xylem
pith
©1996 Norton Presentation Maker, W. W. Norton & Company
Dicot stem anatomy: vascular cambium adds secondary tissues
©1996 Norton Presentation Maker, W. W. Norton & Company
Each year the vascular cambium make a new layer of
secondary xylem and secondary phloem
Dicot stem anatomy: four year-old stem (3 annual growth rings)
phloem etc.
= bark
All of these
tissues
were
added by
the
vascular
cambium!
xylem = wood
©1996 Norton Presentation Maker, W. W. Norton & Company
Figure 36.29 Page 810
See also part (a)
or less
competition
in forest?
cambium
phloem
or more
competition
in forest?
Figure 36.0 Page 791
periderm
phloem
cambium
= bark
heartwood
pith
Two Xylem Conducting Cells: tracheid developmental sequence
Annular Helical Pitted
When flowering plants are
young, water needs are
limited, tracheids suffice.
The walls are strengthened
with secondary thickenings
including lignin.
Protoxylem have
stretchable annular or
helical thickenings.
Metaxylem have reticulate
or pitted and fully rigid
walls.
Tracheids have end walls
and flow between cells is
through pits.
©1996 Norton Presentation Maker, W. W. Norton & Company
Compare Fig. 36.26 Page 806
Two Xylem Conducting Cells: xylem vessel evolution
plesiomorphic
apomorphic
As flowering plants
age and grow, water
needs increase, and
tracheids need to be
supplemented.
Flowering plants
evolved xylem cells
with larger cell
diameter and
perforated end walls
to increase water
flow.
Vessels have
perforated end walls
or lack end walls, but
lateral flow between
cells is still through
pits.
©1996 Norton Presentation Maker, W. W. Norton & Company
©1996 Norton Presentation Maker, W. W. Norton & Company
Dicot stem anatomy: xylem parenchyma, vessels, and tracheids
The huge vessel transports lots of water longitudinally,
and shows lots of pits for lateral transport
©1996 Norton Presentation Maker, W. W. Norton & Company
Dicot stem anatomy: xylem parenchyma, vessels, and tracheids
The huge vessel transports lots of water longitudinally,
and shows lots of pits for lateral transport
©1996 Norton Presentation Maker, W. W. Norton & Company
Secondary xylem: cross sections of three different species
Vessels, Tracheids have different distribution patterns.
Some produce big vessels only in spring wood
Others produce vessels year-round.
Dicot stem anatomy: woody stem circulation
This sketch is
showing the
importance of
lateral transport.
In both
transpiration and
translocation
materials must
move radially to
the interior and
to the exterior as
well as up and
down the plant.
O2 in and CO2 out
©1996 Norton Presentation Maker, W. W. Norton & Company
©1996 Norton Presentation Maker, W. W. Norton & Company
Dicot stem anatomy: 2-year old stem showing ray and periderm
phloem
Rays transport sugar from the phloem toward the interior…
…to keep pith and xylem parenchyma fueled.
Rays transport water and minerals from the xylem to the exterior…
…to keep the periderm, cortex, and phloem parenchyma hydrated.
Xylem and Phloem: tissues with many cell types but conduction function
toward pith
radial
transport
main
transpiration
flow
toward cortex
main
translocation
flow
©1996 Norton Presentation Maker, W. W. Norton & Company
Mendocino Tree (Coastal Redwood) Sequoia sempervirens
Ukiah, California
112 m tall (367.5 feet)!
This tree is more
than ten times taller
than is “theoretically
possible” based
solely upon the
length of the column
of uncavitated water.
How could this be
achieved?
http://www.nearctica.com/trees/conifer/tsuga/Ssemp10.jpg
Transpiration in a tall tree
has at least 3 critical
components:
Evaporation: pulling up water from above
Capillarity: climbing up of water within xylem
Root Pressure: pushing up water from below
©1996 Norton Presentation Maker, W. W. Norton & Company
Transpiration: root pressure (osmotic “push”)
Solutes from
translocation of
sugars
accumulate in
roots.
guttation
Water from the
soil moves in by
osmosis.
Accumulating
water in the
root rises in the
xylem.
This is not “dew” condensing!
Water escapes
from
hydathodes.
Transpiration: root pressure (osmotic “push”)
The veins (coarse and
fine) show that no cell in
a leaf is far from xylem
and phloem (i.e.water
and food!).
The xylem of the veins
leaks at the leaf margin
in a modified stoma
called the hydathode.
These droplets are
xylem sap.
http://img.fotocommunity.com/photos/8489473.jpg
Root pressure accounts
for maybe a half-meter
of “push” up a tree
trunk.
Capillarity: maximum height of unbroken water column
glass tube
vacuum created
gravity pulls
water down
10.4m
atmospheric pressure
keeps water in tube
water
The small diameter of
vessels and tracheids
and the surface
tension of water
provide capillary
(“climb”).
Cohesion of water,
caused by hydrogen
bonds, helps avoid
cavitation.
A tree taller than
10.4 m would need
some adaptations to
avoid “cavitation”
Conifer stem anatomy: pine xylem tracheids with pits, xylem rays
vascular
cambium
tracheids with pits
In spite of the
limitations of
tracheids-only
xylem, conifers
are among the
tallest of trees!
ray parenchyma
©1996 Norton Presentation Maker, W. W. Norton & Company
Conifer stem anatomy: bordered pits as “check-valve” for flow
P
low
P
high
These pit
features allow
conifers to be
very tall and still
avoid cavitation
in their xylem
cells.
As pressures
change between
adjacent cells,
the torus
movement
blocks
catastrophic flow
that would result
in cavitation.
©1996 Norton Presentation Maker, W. W. Norton & Company
Transpiration: evaporation (“pull”)
water
Water
evaporating
from a porous
clay cap also
lifts the
mercury!
mercury
Transpiration
can lift the
mercury
above its
normal
cavitation
height!
vacuum
76 cm
mercury
Grown in 32PO4 (radioactive phosphorus) 1 hour
“Cold” medium 90 hours
new
growth
black
Is phosphate uptake from soil:
transpiration or translocation?
In xylem or phloem?
©1996 Norton Presentation Maker, W. W. Norton & Company
“Cold” medium 6 hours
Is phosphate mobilization from
lower leaf:
transpiration or translocation?
In xylem or phloem?
Translocation: How solutes move in phloem
High Pressure
Leaf
Root
active
transport
plasmodesmata
Low Pressure
Modified from: ©1996 Norton Presentation Maker, W. W. Norton & Company
Translocation: How solutes move bidirectionally in phloem
Low Pressure
Leaf sugars
amino acids
Developing
leaves,
apical bud,
flowers
fruits
High
Pressure
Low Pressure
Modified from: ©1996 Norton Presentation Maker, W. W. Norton & Company
Lateral
buds,
stems,
roots, root
tip
Transpiration
Evaporation:
Water evaporates from
mesophyll into
atmosphere.
Water molecules are
pulled up the xylem by
virtue of cohesion.
Capillarity:
Water climbs in the
xylem cell walls by
adhesion.
Water molecules
follow by cohesion.
Node
Internode
Apical bud
Axillary bud
Carbohydrate
etc.
Node
Leaves
Branch
Stem
Transpiration
Translocation
Lateral roots
Root Pressure:
Water moves into the
root because of
solutes from phloem.
Pressure pushes the
water up the stem.
Water and
Minerals
Taproot
Figure 36-3 Page 793
Node
Internode
Apical bud
Axillary bud
Carbohydrate
etc.
Node
Leaves
Branch
Stem
Transpiration
Translocation
Lateral roots
Water and
Minerals
Taproot
Figure 36-3 Page 793
Translocation
Leaf = Source
Photosynthesis
produces solutes.
Solutes loaded into
phloem by active
transport.
Water follows by
osmosis, increasing
pressure.
Root (etc.) = Sinks
Solutes removed from
phloem by active
transport.
Water follows by
osmosis, reducing
pressure.
Pressure = Bulk Flow
The pressure gradient
forces phloem sap away
from leaves to all sinks
(bidirectionally).