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24 Cards in this Set
- Front
- Back
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Which 2 tissues are important for mass transport in plants? |
Xylem tissue Phloem tissue |
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What is xylem tissue responsible for? |
Transporting water and mineral ions up the plant from root to leaves. Only 1 direction-up |
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What is the phloem tissue responsible for? |
Transporting assimilates (e.g. sucrose) up and down the plant. Goes up and down. |
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What is xylem tissue composed of? |
Xylem vessles |
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What do xylem vessels contain? |
Dead cells No end walls No nucleus or cytoplasm Walls thickened Lignin thickening Bordered pits |
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How are dead cells arranged and what can they be described as? |
They're aligned end to end. Apoplast= non-living |
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What do no end walls do? |
They form continuous tubes from root to leaf |
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What does the lack of nuclei and cytoplasm allow for? |
Hollow tubes |
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What is the name for walls thickened? |
Lignified |
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Why are wall lignified? |
To prevent tubes from collapsing and waterproof the walls of the cells |
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Where does lignin thickening take place? |
In the cell walls
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What does lignin thickening do? |
It forms patterns which can be spirals, rings (annular) or a networks of broken rings (reticulate). |
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What does this prevent? |
This prevents the vessel from becoming too rigid and allows flexibility in the stem and branch. |
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What are bordered pits and what do they do? |
In some places, the lignification is incomplete, leaving pores in the wall of the vessel. This allows water to pass into an adjacent vessel or a living part of the plant, |
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What theory can explain water movement up the plant? |
The cohesion-tension theory |
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What is step 1 in this theory? |
Water evaporates from the leaf surface in a process called transpiration. |
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What is step 2 in this theory? |
This creates tension in the xylem |
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What is step 3 in this theory? |
Water molecules are cohesive (stick together) due to hydrogen bonds between molecules so when some are pulled into the leaf, others follow. This means the whole column of water in the xylem is pushed upwards. |
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What is step 4 of this theory? |
Water then enters the stem through the roots |
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What happens to minerals? |
They're actively transported into the xylem |
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What do minerals do in the xylem? |
They lower the water potential and water follows by osmosis. |
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What does the movement of water out of the xylem do? |
It creates low hydrostatic pressure and thus tension. |
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What does this allow? |
Water to move across the leaf via osmosis and water vapour then diffuses out of the leaf |
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How are root hair cells adapted? |
Many mitochondria and carrier proteins
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