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10 Cards in this Set
- Front
- Back
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What are xylem vessels? |
Long hollow tubes to transport water. |
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What are phloem vessels? |
Elongated living cells with very little cytoplasm and permeable ends. They actively transport the products of photosynthesis to all parts of the plant that need it. This is mostly sucrose but also amino acids and fatty acids. |
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What is the process of root pressure? |
Water enters the roots through osmosis and pushes the water upwards. Evidence of this is that a sap exudes from a cut stem. |
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What is the process of Cohesion / Transpiration? |
Water evaporates from the leaves, this pulls a column of water molecules up through the xylem due to cohesive forces between water molecules. Evidence of this is a photometer and a change in diameter of the stems during the day. |
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What is transpiration affected by? |
- Air temperature - increases the evaporation of water, therefore increasing the concentration gradient of water vapour. - Humidity - decreases the concentration gradient of water vapour. - Wind speed - wind moves water vapour away therefore increasing the concentration gradient. - Light - stomata close in the dark. - Loss of tugor - water availability. |
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What is a companion cell? |
It contains all the organelles; mitochondria for active transport, Golgi and endoplasmic reticulum or synthesis. |
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What are sieve tubes? |
Thin cytoplasm for maximum transport. |
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What is a sieve plate? |
Perforated cell walls. |
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What is the symplastic route? |
- When water enters the root hair cell, due to lower water potential than that of the soil, it increases the water potential of that cell in comparison to that of the adjacent cell. - Water therefore moves by osmosis into the next cell. - It continues to move through the cytoplasm of each cell until it reaches the endodermis. It passes through the endodermis and into the xylem. |
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What is the apoplastic route? |
- Water is absorbed by the cellulose cell walls and passes rapidly between the cortex cells until it reaches the endodermis. - They pass into the endodermis due to a waterproof layer called the casparian strip. - From there, it passes into the xylem as before. |
