long hollow structures made by fusing several columns of cells together end by end
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what does size have to do with the need for transport systems?
some trees are incredibly large and need transport systems in order to move nutrients up to the leaves from the roots that would be able to diffuse on time without.
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what does SA:V have to do with the need for transport systems?
some parts of the plant have very small SA:V so these parts cannot rely on diffusion alone to move the nutrients to the cells.
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what do xylem fibres do?
they offer extra mechanical support for the plant
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how are xylem fibres structured?
long cells with lignified second walls
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what do xylem parenchyma do?
store food around the xylem vessles and contain tannin deposits
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what is the structure of lignin?
can form rings, spirals or solid tubes with lots of small unlignified areas called bordered pits where water leaves the xylem
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in which direction is the flow of xylem
up towards the leaves
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what is the function of the phloem?
living tissue that transports food in the form of organic solutes around the plant from the leaves where they are made via photosynthesis
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which direction is the flow of phloem?
any direction
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what are the structure of sieve tubes?
long hollow structure made up of lots of cells fused end to end, in areas between the cells the walls become perforated creating sieves to allow contents to flow through
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what happens when the pores of the sieve tubes become too large?
the nucleus, vacuole tissue and other organelles begin to break down causing the phloem to become full with phloem sap and the mature phloem cells have no nucleus
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what is the function of the companion cell?
they act as life support for the sieve tubes that have lost their functions
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what is the structure of the companion cells?
they're attached to the sieve tubes by plasmodesmata
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Other cards in this set
Card 2
Front
what does size have to do with the need for transport systems?
Back
some trees are incredibly large and need transport systems in order to move nutrients up to the leaves from the roots that would be able to diffuse on time without.
Card 3
Front
what does SA:V have to do with the need for transport systems?
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