Transportation In Plants

Moving Materials In Animals How do most animals move materials around their body? How do most animals move materials around their body? – Circulatory system – Blood vessels like vein, arteries, and capillaries What powers the movement? What powers the movement? – Contracting muscles of the heart – Contracting body muscles pinching veins What forces work against the movement? What forces work against the movement? – Thickness of fluid – Gravity

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 materials

Parts of The Transport System: Roots Roots  designed to absorb water and minerals from the soil Roots  designed to absorb water and minerals from the soil – What minerals do we need? – Nitrates, Phosphates, Mg 2+, etc… Root cap  protective cells to help push through soil Root cap  protective cells to help push through soil Root tip  mass of rapidly dividing cells so roots can grow 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) 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 Cortex  stores starch; passes water and minerals to xylem Xylem  one-way transporting of water/minerals from roots to leaves Xylem  one-way transporting of water/minerals from roots to leaves Phloem  two-way transporting of sucrose, amino acids, and hormones Phloem  two-way transporting of sucrose, amino acids, and hormones

Moving Water to the Xylem How does water get into the roots? How does water get into the roots? – Absorbed through osmosis by root hairs Water must pass through many layers: epidermis, cortex, endodermis, and pericycle 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 A) Apoplast pathway  water passes along space in cell walls B) Symplast pathway  water passes through cytoplasm of cells and then through the plasmodemata B) Symplast pathway  water passes through cytoplasm of cells and then through the plasmodemata

Moving Water to the Xylem 2) Cortex  Endodermis  Stele: Endodermis  cells covered in suberin (waterproof wax); ring forms Casparian strip 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 Passage cells  cells with no suberin that only allow water through the symplast pathway – Why have this? Regulation; filter out unwanted molecules Regulation; filter out unwanted molecules 3) Pericycle  Xylem vessels: Water moves by symplast pathway towards hollow xylem vessels from the pericycle Water moves by symplast pathway towards hollow xylem vessels from the pericycle What powers all this movement? What powers all this movement? – Osmosis

Tissue Layers of Xylem 4 cell types: 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 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 areas 3)Fibers  – Dead lignined cells used for support of xylem 4)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 Shoots  designed to support growing branches/ leafs and transport material Vascular bundle  main transport system made of phloem, xylem, and cambium 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 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 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 Leafs  designed to use water/minerals to do photosynthesis – What is the product of photosynthesis? glucose glucose – Why is glucose changed to sucrose before going to phloem? Sucrose is more soluble Sucrose is more soluble Stoma  openings in leafs that allow gas exchange Stoma  openings in leafs that allow gas exchange – What gases are exchanged? O 2 and CO 2 O 2 and CO 2 – What is also lost through the stoma? Water Water

Transpiration Transpiration  movement of water from roots to leaves through the evaporation of water from the leafs 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? Where does the strength come from to pull water against gravity? – Hydrogen bonds Two forces are needed: Two forces are needed: 1)Cohesion  H-bonds between water molecules; water sticks together 2)Adhesion  H-bonds between water molecules and other surfaces; water sticks to xylem vessel Mass flow  continuous flow of water through xylem 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 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 Root pressure  force of water flowing into the xylem in the roots – How can roots increase root pressure? Raise conc. of solutes in xylem 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? How can we measure transpiration in plants? 1)Measure how much water is released from plant Fairly difficult to do Fairly difficult to do 2)Measure how much water is absorbed by plant Fairly simple to do Fairly simple to do Potometer  measures the amount of water absorbed into a plant by the movement of an air bubble a meter 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? Plants have constantly monitor how much H2O is in their leaves. Why? – Need H2O for photosynthesis What factors will effect the rate of transpiration? What factors will effect the rate of transpiration? 1)Temperature  water evaporation 2)Light intensity  increase temp and photosynthesis rate 3)Wind  faster evaporation 4)Humidity  higher % of water in air means less transpiration

Adapting Transpiration What environments would cause the highest transpiration rates? What environments would cause the highest transpiration rates? – Hot, dry, and bright areas; deserts Xerophytes  desert plants Xerophytes  desert plants 1)Smaller leaf surface area  less water loss 2)Thick, waxy cuticle  less water loss 3)Water-storing tissue 4)Large root system  absorb more water 5)Shiny cuticle  reflects sunlight 6)Stomata closed during the day  get CO2 at night time

Adapting Transpiration What environment wouldn’t require much transpiration regulation? What environment wouldn’t require much transpiration regulation? – In or on a body of water Hydrophytes  grow in or on water Hydrophytes  grow in or on water 1)Few xylem  absorb water directly 2)No root hairs  roots act are anchors 3)No cuticle  no need to limit water loss 4)Stomata on upper side of leaf 5)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? What environment is transpiration most consistent? – Normal temperatures and water supply Mesophytes  garden plants Mesophytes  garden plants 1)Normal amount of xylem 2)Waxy cuticle to lower water loss 3)Med. sized root system 4)Standard plant adaptations 5)Many produce flowers for pollination

Sap and Water Sap  think sugar solution inside phloem; used to make syrup 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 Most sap is moving from leafs to roots and follows with gravity Why is the movement of water a major concern for plants? 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 Moss  can only grow 1 m tall because it lacks proper xylem Giant redwoods  114 m tall! Giant redwoods  114 m tall!

Moving Nutrients Translocation  transport of soluble organic substances (assimilates) up and down in a plant Translocation  transport of soluble organic substances (assimilates) up and down in a plant Phloem tissue: Phloem tissue: 1)Sieve elements 2)Companion cells Transport by mass flow, however it is an active process Transport by mass flow, however it is an active process Active loading  the moving of sucrose into sieve elements powered by ATP Active loading  the moving of sucrose into sieve elements powered by ATP Materials follow a source/sink system: 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 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 Companion cells  a normal plant cell connected to at least 1 sieve element – Lots of mitochondria and ribosomes. Why? Very metabolically active 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: Mesophyll cells  Companion cells: – Sucrose is carried by water through symplast pathway or apoplast pathway Entering companion cells: Entering companion cells: – H+ pump uses ATP to push H+ out of companion cells Sets up a H+ conc. gradient Sets up a H+ conc. gradient – H+ diffuse back in through a co- transport protein; pull sucrose inside with them Entering sieve elements: Entering sieve elements: – Sucrose diffuses into sieve elements through plasmodesmata and join mass flow Leaving sieve elements: Leaving sieve elements: – Sucrose enters companion cell by diffusion through plasmodesmata Entering Root cells: 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? 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 basic 2)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. Phloem CharacteristicXylemPhloem Material TransportedWater Ions/Minerals Sucrose Proteins Organic Substances Force Powering Transport Transpiration Cohesion Adhesion Source/Sink Gravity Direction of TransportOnly from roots to leaves In all directions in plant Type of Cells In TissueMostly dead cells with living cell for support Only living cells Reaction To DamageRedirect xylem solution to other xylem elements Releases Callose (β 1,3) to clot hole quickly