transportation in plants. moving materials in animals how do most animals move materials around...
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Moving Materials In Plants How do plants move materials around their bodies? How do plants move materials around their bodies? – Vascular bundle Xylem water/ions Xylem water/ions Phloem nutrients/hormones Phloem nutrients/hormones – Narrow tubes made of hollowed out plant cells Only cell walls remain Only cell walls remain What powers the movement? What powers the movement? – Concentration gradients – Gravity – Transpiration What forces work against the movement? What forces work against the movement? – Thickness of fluid – Gravity Why do plants not require a heart? Why do plants not require a heart? – Slower metabolism; don’t require a fast transport of materialsTRANSCRIPT
Transportation In Plants
Moving Materials In Animals• How do most animals move
materials around their body?– Circulatory system – Blood vessels like vein, arteries,
and capillaries • What powers the movement?– Contracting muscles of the heart– Contracting body muscles pinching
veins• What forces work against the
movement?– Thickness of fluid– Gravity
Moving Materials In Plants• How do plants move materials around
their bodies?– Vascular bundle
• Xylem water/ions• Phloem nutrients/hormones
– Narrow tubes made of hollowed out plant cells• Only cell walls remain
• What powers the movement?– Concentration gradients– Gravity– Transpiration
• What forces work against the movement?– Thickness of fluid– Gravity
• Why do plants not require a heart?– Slower metabolism; don’t require a fast
transport of materials
Parts of The Transport System: Roots• Roots designed to absorb water and
minerals from the soil– What minerals do we need?– Nitrates, Phosphates, Mg2+, etc…
• Root cap protective cells to help push through soil
• Root tip mass of rapidly dividing cells so roots can grow
• Epidermal cells outer layer of tissue; have root hairs (thin extensions of outer root cells that absorb water and minerals)
• Cortex stores starch; passes water and minerals to xylem
• Xylem one-way transporting of water/minerals from roots to leaves
• Phloem two-way transporting of sucrose, amino acids, and hormones
Moving Water to the Xylem• How does water get into the
roots?– Absorbed through osmosis by
root hairs• Water must pass through
many layers: epidermis, cortex, endodermis, and pericycle
1) Root hairs Epidermis Cortex: A) Apoplast pathway water passes along space in cell walls B) Symplast pathway water passes through cytoplasm of cells and then through the plasmodemata
Moving Water to the Xylem2) Cortex Endodermis Stele:• Endodermis cells covered in
suberin (waterproof wax); ring forms Casparian strip
• Passage cells cells with no suberin that only allow water through the symplast pathway– Why have this?
• Regulation; filter out unwanted molecules
3) Pericycle Xylem vessels:• Water moves by symplast
pathway towards hollow xylem vessels from the pericycle
• What powers all this movement?– Osmosis
Tissue Layers of Xylem• 4 cell types:1) Vessel elements
– Hollow tubes made from dead plant cells– Coated in lignin (waterproof protein)– Pits non-lignined sections of cell walls; allow
movement of water out by osmosis• Can form unique patterns
2) Tracheids– Primitive vessel elements with tapered ends– Holds water in place by adhesion when
transpiration is slow or stops– Pits help transport water across plant to other
areas3) Fibers
– Dead lignined cells used for support of xylem4) Parenchyma cells
– Living plant cells between vessel elements; support and storage
– Contain no chloroplasts
Parts of The Transport System: Shoots• Shoots designed to support
growing branches/ leafs and transport material
• Vascular bundle main transport system made of phloem, xylem, and cambium
• Cambium produces more phloem/xylem tubes as the diameter of plant grows; supports plant
• Epidermis thin single layer of cells covered with a waxy cuticle to prevent water loss
Parts of The Transport System• Leafs designed to use
water/minerals to do photosynthesis– What is the product of
photosynthesis?• glucose
– Why is glucose changed to sucrose before going to phloem?• Sucrose is more soluble
• Stoma openings in leafs that allow gas exchange– What gases are exchanged?
• O2 and CO2
– What is also lost through the stoma?• Water
Transpiration • Transpiration movement of water from
roots to leaves through the evaporation of water from the leafs– Creates a PULL, or suction
• Where does the strength come from to pull water against gravity?– Hydrogen bonds
• Two forces are needed:1) Cohesion H-bonds between water
molecules; water sticks together2) Adhesion H-bonds between water
molecules and other surfaces; water sticks to xylem vessel
• Mass flow continuous flow of water through xylem– Increases with temp., wind, and
humidity
Pressure Systems• Hydrostatic pressure force pushing
down on top of water in xylem– Reducing this pressure draws xylem
fluid up against gravity– Reduced by the movement of water
out of the xylem into the leaves• Root pressure force of water
flowing into the xylem in the roots– How can roots increase root
pressure?• Raise conc. of solutes in xylem
– Ions are activity transported into the xylem to lower the water potential
– Water moves into xylem from roots by osmosis
Measuring Transpiration• How can we measure
transpiration in plants?1) Measure how much water is
released from plant• Fairly difficult to do
2) Measure how much water is absorbed by plant• Fairly simple to do
• Potometer measures the amount of water absorbed into a plant by the movement of an air bubble a meter– Can expose plant to different
conditions to explore effects of wind, light intensity, temp., and humidity
Transpiration Rate• Plants have constantly monitor
how much H2O is in their leaves. Why?– Need H2O for photosynthesis
• What factors will effect the rate of transpiration?
1) Temperature water evaporation
2) Light intensity increase temp and photosynthesis rate
3) Wind faster evaporation4) Humidity higher % of water in
air means less transpiration
Adapting Transpiration • What environments would cause
the highest transpiration rates?– Hot, dry, and bright areas; deserts
• Xerophytes desert plants1) Smaller leaf surface area less
water loss2) Thick, waxy cuticle less water loss3) Water-storing tissue4) Large root system absorb more
water5) Shiny cuticle reflects sunlight6) Stomata closed during the day
get CO2 at night time
Adapting Transpiration • What environment wouldn’t require
much transpiration regulation?– In or on a body of water
• Hydrophytes grow in or on water1) Few xylem absorb water directly2) No root hairs roots act are anchors3) No cuticle no need to limit water
loss4) Stomata on upper side of leaf5) Air pockets in stem gases diffuse in
water slower, so air pockets increase diffusion rates and can store gases till needed
Adapting Transpiration • What environment is
transpiration most consistent? – Normal temperatures and water
supply• Mesophytes garden plants1) Normal amount of xylem2) Waxy cuticle to lower water loss3) Med. sized root system4) Standard plant adaptations5) Many produce flowers for
pollination
Sap and Water• Sap think sugar solution inside
phloem; used to make syrup – Why is thickness of sap not a
major concern of plants?• Most sap is moving from leafs to
roots and follows with gravity
• Why is the movement of water a major concern for plants?– Must move water upward against
gravity – Only major limit on tree height
• Moss can only grow 1 m tall because it lacks proper xylem
• Giant redwoods 114 m tall!
Moving Nutrients • Translocation transport of soluble
organic substances (assimilates) up and down in a plant
• Phloem tissue:1) Sieve elements2) Companion cells• Transport by mass flow, however it
is an active process• Active loading the moving of
sucrose into sieve elements powered by ATP
• Materials follow a source/sink system:– Source high conc. (leaves)– Sink low conc. (stem/roots)
Phloem Tissue • Sieve elements tube-like cells
similar to xylem but made of living cells– Basic organelles; no nucleus or
ribosomes– Sieve plate porous divider
between each cell that allows free movement of materials
• Companion cells a normal plant cell connected to at least 1 sieve element– Lots of mitochondria and
ribosomes. Why?• Very metabolically active
– Spends ATP to pull in sucrose from other cells; pass on to sieve element through plasmodesmata
Loading Sucrose• Mesophyll cells Companion cells:
– Sucrose is carried by water through symplast pathway or apoplast pathway
• Entering companion cells:– H+ pump uses ATP to push H+ out of
companion cells• Sets up a H+ conc. gradient
– H+ diffuse back in through a co-transport protein; pull sucrose inside with them
• Entering sieve elements:– Sucrose diffuses into sieve elements
through plasmodesmata and join mass flow
• Leaving sieve elements:– Sucrose enters companion cell by
diffusion through plasmodesmata• Entering Root cells:
– Actively pumped into cells and stored in large vacuole is conc. of sucrose is high
Evidence for Loading Sucrose• What characteristics would
you expect to find around the phloem if “active loading” is occurring?
1) Phloem sap has a basic pH (about 8)– H+ pushed out of cell, so inside
becomes more basic2) Electrical potential across the
plasma membrane (-150 mV)– Just like in nerves, high conc. Of
+ ions outside makes electrical potential
3) ATP is high conc.– Need for active transport
Xylem Vs. PhloemCharacteristic Xylem Phloem
Material Transported WaterIons/Minerals
SucroseProteins
Organic Substances Force Powering
TransportTranspiration
CohesionAdhesion
Source/SinkGravity
Direction of Transport Only from roots to leaves
In all directions in plant
Type of Cells In Tissue Mostly dead cells with living cell for support
Only living cells
Reaction To Damage Redirect xylem solution to other xylem
elements
Releases Callose (β 1,3) to clot hole quickly