Transport in plants

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  • Created by: LivviR123
  • Created on: 08-04-18 16:51
What are the three main reasons why plants need transport systems?
High metabolic demand, low SA:V ratio, large size
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What is the vascular system?
transport vessels running through the stem, roots and leaves of a dicot
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What are vascular bundles?
How transport tissues are arranged together in the leaves, stems and roots of dicots
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Two main functions of xylem?
Support and transport of water and mineral ions
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Which direction is the flow of materials in the xylem?
Just up
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What are xylem vessels?
Main structures of the xylem
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How are xylem vessels made?
by fusing together several columns of cells end to end
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What does xylem parenchyma do?
pack around xylem vessels, store food, contain tannin deposits
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What are xylem fibres?
long cells w. lignified secondary walls that provide extra mechanical strength
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How can lignin can be laid down in the walls of xylem vessels?
Rings, spirals, relatively solid tubes w lots of bordered pits
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What does phloem transport?
Food in the form of organic solutes
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Which direction is the flow of materials in the phloem?
Up and down
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What are the sieve tube elements?
Main transporting vessels of the phloem
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How are phloem sieve tubes made?
Many cells joined end to end to form a long, hollow structure
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What differs between phloem tubes and xylem tubes?
Phloem tubes are not lignified
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Where are sieve plates and what do they do?
Where walls become perforated, allow phloem contents through
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How are companion cells linked to sieve time elements?
By plasmodesmata
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Function of companion cells
to act as the 'life support system' for the sieve tube cells
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What are sclereids?
cells with extremely thick walls
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What does turgor pressure provide?
A hydrostatic skeleton supporting stems and leaves
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What does turgor drive?
Cell expansion
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three other roles of water
cooling, transporting, photosynthesis
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How are root hair cells well adapted?
microscopic, thin later, large SA:V, maintains WP gradient
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What is the symplast pathway?
the continuous cytoplasm of the living plant cells connected through plasmodesmata
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What is the apoplast pathway?
movement of water through the cell walls & intercellular spaces
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What is the endodermis?
The layer of cells surrounding vascular tissue?
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Why is the endodermis particularly noticeable in the roots?
Presence of the Casparian *****
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What is the Casparian ***** made of?
Suberin
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Which pathway is disrupted by the Casparian *****?
Apoplast pathway- water is forced into the symplast pathways
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What is root pressure?
A push of water up the xylem
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What is transpiration?
Loss of water vapour from stems and leaves by evaporation
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What is translocation?
movement of organic solutes around the plant in the phloem
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What is the transpiration stream?
Movement of water up from the roots to the highest leaves
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What is capillary action?
The process by which water can move up against the force of gravity
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Why does capillary action come about?
because water molecules cohere and adhere
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What is the transpiration pull?
Continuous stream of water water drawn up xylem to replace the water lost by evaporation
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What is cohesion-tension theory?
Model of water moving from the soil up the xylem and across the leaf continuously
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Which piece of equipment is often used to measure transpiration?
a potometer
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Rate of water uptake =
distance moved by air bubble/ time taken for it to move that distance
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Factors affecting transpiration rate
Temp, relative humidity, light, air movement, soil-water availability
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Main sources of assimilates
green leaves & stems, storage organs, food stores in seeds
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Main sinks
growing roots, active meristems, any parts laying down food stores
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What is the symplast route?
Sucrose moving through the cytoplasm of mesophyll cells- passive
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What is the apoplast route?
sucrose travels through cell walls and inter-cell spaces to companion cells
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What are xerophytes?
Plants w. adaptations to survive in dry habitats
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what are hydrophytes
plants w. adaptations to survive in v wet habitats
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Adaptations of xerophytes
Sunken stomata, thick cuticle, hairy leaves, reduced leaves, curled leaves, root adaptations
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Adaptations of hydrophytes
no cuticle, reduced structure, wide & flat leaves, open stomata, air sacs, small roots
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Other cards in this set

Card 2

Front

What is the vascular system?

Back

transport vessels running through the stem, roots and leaves of a dicot

Card 3

Front

What are vascular bundles?

Back

Preview of the front of card 3

Card 4

Front

Two main functions of xylem?

Back

Preview of the front of card 4

Card 5

Front

Which direction is the flow of materials in the xylem?

Back

Preview of the front of card 5
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