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7 Cards in this Set
- Front
- Back
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What is the protoxylem? |
Living tissue capable of growing and stretching as walls not fully lignified; as stem ages and stops growing cell becomes more lignified until the inner part of the cell dies |
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What is the metaxylem? |
Lignified tissue; end walls break down so zylem forms a tube; water moves in and out of the xylem through specialised pits |
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What provides the support in smaller, non-woody cells? |
Parenchyma cell turgidity |
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What is translocation? |
The movement of substances around plants |
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Effects of the xylem's narrow diameter? |
High resistance but also high speed of water |
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What is transpiration, and how does it occur? |
The loss of water vapour from the surface of a plant; water moves via osmosis from xylem through veins to spongy mesophyll where it evaporates through stomata down a conc. gradient into still air and is then blown away by the wind |
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What causes the transpiration stream? |
When water leaves xylem this creates tension in the column of water in the xylem; this tension is transmitted down to the roots due to cohesion, and the dipole nature of water and h-bonds gives the column high tensile strength so it is less likely to break; the molecules adhere strongly to the sides of the xylem; combination of cohesion and adhesion pulls water up xylem and replaces water lost by transpiration |
