Transport in Plants

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What is a dicotyledonus plant (dicot)?
A plant which makes seeds that contain two seed leaf organs that act as food stores for the developing embryo
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What is the function of collenchyma and sclerenchyma?
to give the vascular bundle strength and support
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Describe the vascular bundle in herbaceous dicots.
the bundles are separate (discreet)
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Describe the vascular bundle in woody dicots.
The bundles are separate in young stems but become a continuous ring in older stems/ trunks just under the bark
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What is the main opposing force acting on the stem?
The sideways force of the wind which could lead to snapping
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What is the main opposing force acting on the root?
The uprooting force of leaves and stems being blown in the wind
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What is the function of lignin?
It waterproofs the walls of cells by impregnating them, it strengthens the vessel to keep it open permanently whilst preventing it from being too rigid
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It what way to tracheids differ from xylem vessels?
They have end walls and are made up of elongated cells with tapering ends
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It what three ways can be arranged in the xylem vessel?
It can form annular rings, a spiral or a recticulate (irregular broken ring pattern)
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Why does the phloem need companion cells?
Because in order to maximise the amount of phloem that can be carried the tubes lose most of their organelles meaning they cannot carry out many of their cell functions. The companion cells act as a life support system.
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How are the companion cells and sieve tube elements linked?
By fine strands in the cytoplasm called plasmodesmata
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which pathway of water experiences least resistance? and why?
the apoplast pathway. As water molecules move into the xylem more water molecules are pulled through the apoplast behind them due to cohesive forces creating a tension that means there is a continuous flow through the open structure of the cell wall
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When is the apoplast pathway used?
When transpiration rates are high
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Define water potential.
The tendency of water to move from one place to another.
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What is the Casparian ***** made of?
A waxy waterproof material called suberin
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What is guttation and what does it provide evidence for?
Guttation is the secretion of droplets from special pores at the end of leaves (particularly at night when transpiration rates are low) provides evidence of root pressure independent of transpiration
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Why does water move up the xylem by mass flow?
Because cohesive and adhesive forces cause the water to move in a continuous column.
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In what conditions is root pressure a significant force?
100% humidity
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How is water lost during 100% humidity?
Water can be forced up the stem due to a positive pressure from below- solutes are actively transported into the roots causing water to enter by osmosis. This increases the hydrostatic pressure in the root forcing water up
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Why do halophytes exhibit xerophytic adaptations?
Because of the scarcity of obtainable water due to its high salt content, and the high transpirational losses from the strong so coastal winds
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What does a deciduous plant do?
lose its leaves in the winter
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What is the advantage of xylem vessels having very narrow lumen?
It increases the height to which water can be drawn by capillarity. Water molecules adhere to the walls and cohere to each other
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What is the function of the casparian *****?
prevents potentially toxic solutes from reaching living tissues. The water must pass through the patially permeable membrane preventing toxic solutes in the soil water from entering the living tissue as there are no carrier proteins to admit them.
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Why are the endodermal cells important for ensuring that water flows into the xylem?
They actively transport mineral ions into the xylem vessel lowering the H2O potential of the xylem ensuring there is always a diffusion gradient for water to move into the xylem
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What are cells near the root hair cells known as?
The cortex
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Why does a low temperature decrease the transpiration rate?
The water molecules have less kinetic energy and therefore move out of the stomata more slowly.
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Why is water important to plants?
1) a raw material for photosynthesis 2)provides support by cells turgid 3)transport medium for inorganic mineral ions that the plant needs to produce enzymes 4) It facilitates evaporative cooling of the leaves 5)needed for growth/assimilate transport
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Describe and explain the adaptations of a root hair cell.
Long and thin, providing a large surface area speeding up absorption of water (osmosis) and mineral ions (diffusion/active transport)
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Explain how xylem is adapted for its function.
Formed from dead cells laid end to end creating hollow tubes-water flows uninterrupted. Narrow tubes so capillary action can be effective. Incomplete lignin patterns provide strength but allows xylem to stretch. Bordered pits allow sideways movement.
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In the vascular bundle, what is the name of the layer between the xylem and phloem tissues and what is its function?
Cambium
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In transverse section of a leaf which transport tissue will be on the top?
The xylem
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In a transverse section of a stem which transport tissue will be on the outside?
The phloem
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Define the vascular bundle.
Phloem and xylem vessels found together in 'bundles'
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If you place celery with plenty of leaves into coloured dye what can you observe after a while?
The xylem will become stained with the dye colour as it travels up
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Describe and explain 3 adaptations of hydrophytes such as water lilies
1)Stomata on upper surface of the leaf ensures gas exchange can occur 2) Air spaces, aid buoyancy ensures leaves are at surface to absorb sunlight 3) No waxy cuticle- doesn't prevent H2O loss
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Describe and explain 2 more advanced adaptations of hydrophytes
1) hydathodes allow water droplets to seep out of leaves when water vapour cannot form-ensures mineral ions are still drawn up 5) Aerenchyma has many large airspaces,aids buoyancy, provides low resistance pathway for oxygen to submerged tissues
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Describe the role of the Casparian ***** in creating root pressure.
The Casparian ***** blocks the apoplast pathway forcing water into the symplast pathway. Once the water has entered the medulla it cannot pass back into the cortex. This causes pressure in the medulla to build up forcing water into the xylem.
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What causes the transpiration pull?
Water molecules are polar meaning they attract each other by forces of cohesion. These cohesive forces are strong enough to hold the molecules together in a long continuous column. As molecules are lost from the top of the column, tension is created.
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Why must the xylem vessels be strengthened with lignin?
Because otherwise they would collapse under the tension of the transpiration pull. It also keeps the vessel open when water levels are low which would cause the plants to lose turgor pressure
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What causes capillarity?
The polar nature of water molecules mean that they also adhere (are attracted) to the vessel walls. Because the vessels are so narrow these forces of attraction pull the water up the cokumn.
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In what type of plants are tracheids present?
They are the main conducting tubes in primitive plants e.g. conifers and ferns
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Other cards in this set

Card 2

Front

What is the function of collenchyma and sclerenchyma?

Back

to give the vascular bundle strength and support

Card 3

Front

Describe the vascular bundle in herbaceous dicots.

Back

Preview of the front of card 3

Card 4

Front

Describe the vascular bundle in woody dicots.

Back

Preview of the front of card 4

Card 5

Front

What is the main opposing force acting on the stem?

Back

Preview of the front of card 5
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