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8 Cards in this Set
- Front
- Back
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which 4 types of cell make up the xylem
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vessels (elements)
tracheids fibres parenchyma |
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how does the structure of a narrow xylem vessel element that is thickened with rings allow it to transport water and mineral ions
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- Thin cell wall - is stretched as the plant grows
-rings of lignified cell wall - provides support and prevent collapse -no cell contents - empty tube gives little resistance to the flow of water |
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how does the structure of a wide xylem vessel element with pits allow it to transport water and mineral ions
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-large empty lumen - allows flow of large volumes of water
-thick cell wall - strengthened with lignin to withstand tension and prevent vessel from collapsing -pits in the cell wall - to allow water to flow laterally between xylem vessels - no cell contents - empty tube gives little resistance to the flow of water |
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what are vessels and tracheids composed of and how are they formed?
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-composed of dead, elongated cells with pits in them.
- vessels are long, tubular structures formed by the end-to-end fusion of vessel elements and the breakdown of their end walls. |
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what is the function of the fibres and parenchyma
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provide support to the tissue
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which 4 types of cell make up the phloem?
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- sieve tub elements
- companion cells - fibres - parenchyma |
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What is the function and structure of sieve tubes and how are they formed?
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- formed by the end-to-end fusion of sieve tube elements
-they lack a nucleus - the cytoplasm forms a thin layer around the periphery of the cell to allow movement of phloem sap through the centre - the cell walls at the ends of each cells are perforated to form sieve plates, which allow the cytoplasm from one cell to run into adjacent cells. - their function is to transport organic solutes E.G sucrose and amino acids |
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What is the function and structure of companion cells?
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- lie next to sieve tubes and are linked to them by plasmodesmata which allows sucrose to flow into the sieve tube
- contain many cell organelles, esp mitochondria which provide the energy to move sucrose into the sieve tube - involved in loading and unloading of the sieve tubes with solutes |
