9.1 Transport in the Xylem of Plants - BioNinjabioninja.com.au/worksheets/topic 9.1 worksheet...
Transcript of 9.1 Transport in the Xylem of Plants - BioNinjabioninja.com.au/worksheets/topic 9.1 worksheet...
9.1 TransportintheXylemofPlants
PlantStructure
Labelthediagramoftheleaftissueofaplant
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Explainthelocationofthemesophyll(palisadeandspongy)andvascularbundlewithintheleaf
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VascularBundle:……………………………………………………………………………………………………………………………..
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Identifythefollowingplanttissues(monocotvsdicot;rootvsstem)
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Vascular bundle
Xylem
Phloem
Epidermis (lower)
Waxy cuticle
Guard cell
Stoma
Palisade mesophyll
Spongy mesophyll
On the upper surface of the leaf, the cells are packed tight and rich in chloroplasts
This increases light absorption for photosynthesis
On the lower surface of the leaf, the cells are interspersed by space and near stomata
This increases gas exchange for photosynthesis
Vascular bundles exist centrally between the two layers (allowing equal access)
Have xylem for water transport to leaf & phloem for food transport from leaf
Monocot root Monocot stem Dicot root Dicot stem
XylemStructure
Describethestructureofthexylem
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Drawthestructureofprimaryxylemvesselsinstems
Transpiration
Definetranspiration
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Differentiatebetweenfibrousandtaprootsystems
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Xylem Phloem
Lignin Meta Proto Pit Cellwall
Xylem Phloem
MICROSCOPE DRAWING
Inner lining is composed of dead cells that have fused into a continuous tube
These cells lack a cell membrane, allowing water to enter the xylem freely
The cell walls have thickened cellulose and are reinforced with lignin (annular or spiral)
The outer layer is perforated (has pores), enabling water movement out of xylem
Transpiration is the loss of water vapour from the leaves and stems of the plant
Fibrous roots are thin and very spread out
Tap roots penetrate deeply (for stability) and have many connected lateral branches
Explaintheuptakeofmineralionsintotherootbydirectandindirectactivetransport
DirectActiveTransport
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IndirectActiveTransport
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Outlinetheroleofstomatainregulatingthelevelofevaporationfromtheleaf
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Definecohesionandadhesion
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Explainhowwateristransportedaroundtheplantviaatranspirationstream
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Protein pumps use ATP to translocate ions against their concentration gradient
Proton pumps expel H+ ions into the soil, displacing the cationic minerals from clay
Displaced minerals will passively diffuse into the root (along a concentration gradient)
Anionic minerals may bind to the H+ ions and be reabsorbed with the proton
The transpiration rate can be regulated by the guard cells
which flank the stomata
Guard cells occlude the opening when flaccid
Guard cell turgor is regulated by abscisic acid
Water molecules stick together (by H-bonding)
Water molecules form polar associations with the wall of the xylem vessel
Some of the light energy absorbed by leaves changes into heat, converting water to vapour
The vapour diffuses out and is evaporated, creating a negative pressure gradient in leaves
New water is drawn via the xylem from roots (which enters from soil via osmotic uptake)
Water rises up (against gravity) through xylem vessels via mass flow due to cohesion and adhesion
The flow of water from the roots to the leaf (via the xylem) is called the transpiration stream
Explainhowabioticfactorsaffecttherateoftranspirationinatypicalterrestrialplant
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Identifyfouradaptationsinxerophytesandhalophytesthathelpreduceorincreasetranspiration
Xerophyte Halophyte
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Issue
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Adaptations
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Listthreewayswatertransportcanbemodelledinxylem
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Describehowpotometerscanbeusedtomeasuretranspirationrates
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Increasing ambient temperature causes an increase in the rate of transpiration
Higher temperatures lead to an increase in the rate of evaporation within the mesophyll
Increasing the light intensity to which a plant is exposed increases the rate of transpiration
Increasing light exposure causes more stomata to open to facilitate photosynthetic gas exchange
Increasing the level of wind exposure causes an increase in the rate of transpiration
Wind / air circulation removes water vapour from near the leaf, effectively reducing proximal humidity
Increasing the humidity is predicted to cause a decrease in the rate of transpiration
Less vapour will diffuse from the leaf if there is more vapour in the air
Arid / dry and high temperatures Saline (salty soil / water)
Increased water loss via evaporation
Reduced water uptake via roots
Reduced water uptake due to hypertonic
soil conditions (+ high levels of salt uptake)
Reduced leaves (⬇ evaporation)
Thick cuticles (prevents water loss)
Stomata in pits (traps water vapour)
CAM physiology (open stomata at night)
Cellular sequestration (salt in vacuoles)
Tissue partitioning (leaf abscission)
Salt excretion (active salt removal)
Root level exclusion (avoid salt uptake)
Capillary tubing
Porous pots
Filter paper
Potometers estimate transpiration rate by measuring the rate of water loss or uptake by a plant
They record the distance moved by an air bubble or meniscus to indicate the rate of water uptake