Transport In Plants

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Describe the structure of the Xylem Tissues?
They are long and hollow. Made of dead cells lined on top of each other, with the middle cell walls and membrane broken down to create a hollow tube (ridges of old cell walls can be seen). Walls made of cellulose with extra lignin implanted to give s
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What do xylem do?
They carry water and dissolved minerals UP from roots to leaves.
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Descrbe the Phloem Tissue
Living. Transport dissolved products of photosynthesis (sucrose and amino acids) from where they are made (source) to where they are needed for growth or storage (sink). Flows both ways.
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Describe a root hair cell?
A cell that has an extension of the wall wich increases the surface area for max. absorbtion of water and dissolved minerals.
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Define the term Transpiration.
The loss of water vapour (by evaprtn.) from the leaves through the stoma.
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How does Transpiration work?
Water moves through the plant from the roots to the leaves and is lost to the air as water vapour, or is used by leaf cells in photosynthesis.
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Define the Transpiration stream.
The continuous movement of water from roots to leaves. As water evaps from leaves (tranp) water from the bottom is pulled up creating a constant stream of water.
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Factors affecting Transpiration?
Light Intensity, Humidity, Wind speed, Temperature, Water supply (drought)
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Water uptake process?
Water enters the root hair cell by osmosis. (happens when wp in soil - higher than in root cell).Causes water to move (osmosis) into next cell.Repeated 'til H20 reaches xylem vessels (transport H20 to leaves). H20 also passes through cell walls.
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Pathway of water through Plant
Water moves from the soil into the root across to the stem and them up to leaves. It does this by moving throguh root hair cells, then root cortex cells until xylem vessels are reached which take it up to mesophyll cells in the leaf.
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Two routes into routes?
Appoplastic route (between cells via cell walls) and Symplastic route (cell cytoplasm to cell cytoplasm).
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How does wind affect transpiration?
On a windy day, the water vapour around the leaf gets blown away ; speeding tranprtn. yp.
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How does drought affect Transpiration?
The plant will close it's stoma to reduce the amount of water lost (transprtn. slows).
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How does light intensity affect Transpiration?
Lots of light - stoma open in daylight to allow CO2 in for photosyn ; fast rate of transprtn. as water leaves through open stoma.(but little water, stoma close).
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How does humidity affect Transpiration?
Slows it down. There are already many water molecules in the air (less of a wp gradient).
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How does temperature affect Transpiration?
Hot day (good water supply) peeds up transprt. Stoma open to allow lots of CO2 in for photosyn.
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How is water sucked up xylem?
Transpiration stream, Capillarity, Adhesion, Cohesion.
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Define capillarity
Water rises up narrow tubes due to its 'sticky' nature. narrower the tube, higher the water will climb. (xylem vessels are very narrow). Needs cohesion and adhesion.
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How does cohesion and adhesion **** water up xylem?
Water molecules are held together due to cohesion so as water evaporates from the top, the water below is pulled upwards.
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Define cohesion
Water molecules 'stick' to e/o as they are attracted to other water molecules.
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Define Adhesion
Water molecules stick to the sides of their container as they are attracted to toher materials.
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How guard cells open stoma
When a plant has plenty of water, the guard cells become turgid (thight, water-filled). This causes the guard cells to swell up ; curving away from e/o and opening the stomata.
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How guard cells close stoma
When a plant is short of water, the guard cells are flaccid (vacuoles are 'loose' an not water-filled), closing the stoma.
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Hydrophytes
plants submerged or at surface of water
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Xerophytes
Very dry environments; minimal water (desert plants).
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Adaptations of hydrophytes 1
Divided leaves (large srfc - absrbtn + phtsyn). No protectv. layer (absrb H20, nutrients + dsslvd gss easily). Stoma on upper side of leaf (absorb gases from air). Air spaces in leaves (float). Floating leaves tough (withstand wthr cndtns).
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Adaptations of hydrophtes 2
Some have tall narrow leaves (stay above water in fluctuating water levels). Chlorophyll on upper surface of leaves (absorb sunshine easily)
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Adaptations of xerophytes 1
Deep roots (reach H20 underground). Shallow spreading roots (collect ocacasional rain). Leaves reduced to spines (min. surf-area 4 transpiration). Reduced no. of stoma (reduce transp).
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Adaptations of xerophytes 2
Rolled leaves, leaf hairs & stoma sunk in pits (trap moist air,+se humidity and slowing tranp.) Waxy leaf cuticle (prevents evap - impermeable to H20), stoma open @night & close after midday (prent evap). Succulent tissues (storage for water).
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Translocation deinition?
Movement of sucrose and amino acids up & down phloem; from source to sink.
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Sources
Leaves, stems in some plants.
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Sinks
Roots (respr or storage [potatoes]), fruits, respiring &growing tissues (root tips +shoots)
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When does a plant use active transport?
When the plant needs water but the the roots have a higher wp than the soil - active tranport must be used to **** up water. Otherwie it would lose water.
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Other cards in this set

Card 2

Front

They carry water and dissolved minerals UP from roots to leaves.

Back

What do xylem do?

Card 3

Front

Living. Transport dissolved products of photosynthesis (sucrose and amino acids) from where they are made (source) to where they are needed for growth or storage (sink). Flows both ways.

Back

Preview of the back of card 3

Card 4

Front

A cell that has an extension of the wall wich increases the surface area for max. absorbtion of water and dissolved minerals.

Back

Preview of the back of card 4

Card 5

Front

The loss of water vapour (by evaprtn.) from the leaves through the stoma.

Back

Preview of the back of card 5
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