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74 Cards in this Set
- Front
- Back
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why do plants need a transport system?
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all living things need to take substances from their environment and get rid of waste.
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what do cells need a constant supply of?
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oxygen
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what cells in a plant could survive without a transport system and why?
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epithelial cells because they are close to the surface and can diffuse enough oxygen
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whats the main problem with the roots and the leaves?
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+roots
-can take up water but cant take up sugars +leaves -produce sugars easily but cant take water from the air. hence they both work together |
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what does the vascular tissue do?
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move substance up or down
water travels up only in the xylem food and sugars travel up and/or down in the phloem |
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what does not travel in the vascular tissue?
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gases e.g oxygen and carbon dioxide
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state some properties of the vascular tissues
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-distributed throughout the plant
-doesnt require a pump -xylem and ploem are found together in the vascular bundles -contains other tissues that give support and strength -a specialised tissue |
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describe xylem and phloem in the roots
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-at the centre of a young root
-central core is of xylem, looks like an + or x. -phloem is found in the centre of these sections -provides strength |
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where is the endodermis found?
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around the vascular bundle
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what is inside the endodermis and do they do?
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meristem cells. they are the only cells that divide by mitosis in a plant. they are also stem cells that can specialise into anything required
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what is the pericycle?
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the vascular bundle being surrounded by endodermis that contain meristem cells
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descire xylem and phloem in the stems
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-vascular bundles found near the outer edge of the stem
-in non-woody plants bundles are seperate and discrete -in woody plants bundlesbecome continuous as they age. -provides support and flexibility |
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where are xylem and phloem found in the stem?
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-xylem is found on the inside of vascular bundles
-phloem is on the outsied of the vascular bundles -inbetween phloem and xylem is the cambium -the cambium contains meristem cells |
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describe vascukar bundles in the leaf
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-vascular bundles form the midrib and veins of the leaf
-2 categories of plants: seed leaves or dicotyledons -dicotyledons have a network of branching veins that get smaller as they spread -inside the veins the xylem is on top of the phloem - |
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what does xylem consist of?
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tubes
dissolved minerals fibres |
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how does lignin create xylem vessels?
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-xylem are long and have thick cells
-they are coated in lignin which waterproofs the cell walls -as a result to the waterproffing lignin the cells, end cells and contents die and decay -this leaves a xylem vessel -this is strengthened by the lignin. |
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what patterns do the lignin form and what is their job?
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spiral, annular (rings) or reticulate (broken rings) patterns. their job is to allow flexibility on the vessels.
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how are pits made and what do they do?
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pits are formed when the lignin is not complete and it leaves pores in the walls. they allow water to leave one vessel and pass to a different one
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what are the adaptations of xylem?
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-continous column
-narrow so yube doesnt break and capillary action is effective -lignin ti give support and allow flexibilty when growing or bending -no nucleus or cytoplasm, end walls or contents |
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what is the structure of phloem?
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-transports sugars to one part of the plant to another
-can go up or down -has two types of cells: sieve tube elements and companion cells |
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describe sieve tubes
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-have no nucleus and little cytoplasm
-usually transport sucrose which is dissolved in water to form sap -lined up end to end -contains cross walls at intervals that are perforated to allow sap to flow. called sieve plates -sieve tubes have very thin walls and have 5-6 sides |
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describe companion cells
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-in between sieve tubes
-large nucleus, dense cytoplasm and lots of mitochrondria -carry out metabolic processes needed by sieve tubes, which requires energy -ATP used for loading sucrose into sieve tubes -cytoplasm linked through plasmodesmata |
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what is the plasmodesmata?
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gaps in the cell walls allowing communication and flow of minerals between cells
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what does the pitch for sign stand for?
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water potential
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whaere does water move to and from?
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from a region of hight water potential to an area of low water potential, down a water potential gradient
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what is the water potential of pure water?
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0
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as more salt and/sugars are added what happens to the water potential?
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becomes a negative and gets a bigger naegative the more added
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why do cells never have a water potential of 0?
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because they have cytoplasm that contains solutes
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how does water move?
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by osmosis
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if plant cells are put into pure water what will happen and why?
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-it will take up water by osmosis
-because there is lower water potential outside of the cell than inside, so it moves into the cell where water potential is higher |
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when plant cells take up water why dont they burst?
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-because they have a strong cellulose cell wall
-it becomes turgid but never bursts |
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what is pressure potential in a plant?
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the amount of water pushing on the inside of the wall. as this build up during water intake it reduces intake (influx)
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if a cell is placed in a very strong solution (low water potential) why will it lose water?
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-because the water potential of the cell will be higher than that of the solution.
-therefore it will move to a lower potential which is outside the cell. |
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what is incipient plasmolysis?
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when the cytoplasm of a plant doesnt push against the wall.
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what is plasmolysis?
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when the plasma membrane loses contact with the cell wall.
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if one cell was -800 and the other was -1500 which way would the water move
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-800----->-1500
less----->high |
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what are the 3 routes water can take?
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apoplast
symplast vacuolar |
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describe the apoplast pathway
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-moves through the spaces between the cells.
-spaces between the cells are filled with cellulose molecules -DOESNT pass through plasma membranes or the cells themselves -no nutrients enters the cells at all |
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describe the symplast pathway
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-water enters the cell by the plasma membrane
-travels in the cytpolasm through the plasmodesmata from one cell to the next |
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describe the vacuolar pathway
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-water enters through plasma membrane
-travels from one cell to the next by the plasmodesmata -free to move throughput the cytoplasm AND the vacuoles |
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turgid
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whan a plant cell has absorbes as much water as possible
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plasmolysis
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whan plasma membrane loses contact with the cell wall
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what is transpiration?
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water moves into the plant by the roots, up the stem by the xylem into the leaves and lost by evaporation into the atmosphere
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what is translocation?
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the movement of (assimilates) sugars up and down and side to side in the plant
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what is the casparian strip?
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a tight band around the root cells preventing backflow of water and the water taking the apoplast pathway
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whare is the casparian strip found?
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root cells
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how does the casparian strip work?
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-transpoter cells in the membrane
-lowers the water potential in the xylem so the water from the cortex (outside if the xylem) flows back to the xylem -generates root water pressure -transpiration maintains the water potential pressure -capillary action of water is generated by cohesive property of water |
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how are water molecules attracted to each other?
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by cohesion
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describe how transpiration works
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-waqter molecules attracted to each other by cohesion and form a long chain
-molecules are lost at the top of the chain through the leaves -as this happens the chain is pulled up creating a tension which is strengthened by the ligniated xylem cells. |
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what happens in the xylem if the water column is broken?
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its maintained by another vessel via the pits
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how do minerals enter plant cells?
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by active transport requiring ATP energy
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what is the cortex?
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tissue between the epidermis and the vascular bundles
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describe cohesion
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the attraction between the SAME molecules. in plants its between water molecules and forms a chain of them
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what is adhesion?
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the attraction between DIFFERENT molecules
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where is the stomata and what does it do?
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on the underneath of a leaf, it opens and closes allowing different amounts of gases into and out of the plant
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dewcibe the function of the guard cells
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-either side of the stomata
-when turgid open the stoma -when plasmolysed they close the stomata |
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describe water potential
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-measured in kPa
-moves from high to low water potential down a water potential gradient. e.g-800----->-1500 -generated by water pushing on the cell wall. |
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what are xylem and phloem?
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tissues because they have cells that work together to perform a particular function
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what is the endodermis?
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-around the vascular bundles, containing layers of meristem cells (only cells that divide by mitosis)
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how do you measure photosynthesis?
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with a potometer
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when using a potometer what must you remember to do?
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-cut and join the stem under water
-seal it with vaseline so no water can be lost |
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describe the process of active loading within the phloem
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-companion cells use ATP energy to transport hydrogen ions out of the cells into the surrounding tissues creating a concentration gradient
-hydrogen ions diffuse down a concentration gradient back into the companion cells through cotransporter proteins -hydrogen ions then bring sucrose molecules into the companion cell with them -as the concentration of sucrose builds up in the companion cells it will start to diffuse to the sieve tube elements via the plasmodesmata |
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how does sucrose move along the phloem?
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-sucrose is actively loaded into the sieve tube elements and reduces water potential
-water increases the hydrostatic pressure as it flows by osmosis. -water moves down the sieve tube element from the hydrostatic pressure at the source, to the sink where there is low hydrostatic pressure -sucrose is removed by surrounding cells that require it, increasing the water potential in the sieve tube elements -water then moves out of the sieve tube reducing the hydrostatic pressure. |
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what is the source?
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part of the plant which releases sucrose into the phloem
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what is the sink?
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part of the plant that removes sucrose.
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where is the sink found and what is it used for?
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-found ANYWHERE in the plant
-sucros found at the sink can be used by any cells close by for respiration |
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how does surcose move and does it affect anythng?
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-sucrose moves by diffusion or active transport
-this affects water potential so that molecules can move into surrounding cells -reduces hydrostatic pressure in the phloem at the sink -this process generates MASS FLOW where water can move up OR down in the phloem |
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what affects water loss in plants?
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-light
-temp -presence of cuticles -amount of leaves -number size and position of stomata |
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how does number of leaves affect water loss?
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more leaves=greater surface area therefore more vaour can be lost
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what is a xerophyte?
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a plant that is adapted to reduce water loss so it can survive in very dry condidtions
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name and explain 1 unavoidable loss
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transpiration because when the stomata open for gas exchange there is an easy route for water vapour tp be lost as it moves down a concentration gradient into the atmosphere
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how do plants reduce water loss?
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-they have a waxy cuticle which prevents evapotation through the epidermis
-stomata are found on the bottom of the leaf so the sun cant get to it directly -stomata close at night time when there is no light for photosynthesis -deciduous plants lose their leaves in the winter when it is too cold to photosynthesise and there is little water available due to frozen ground |
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what will happen if plants lose too much water?
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-they will suffer water stress
-cells will loses turgidity and may become plasmolyssed -plants will wilt -eventually die |
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how are xerphytes adapted to living in arid or very dry condition?
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-leaves shaped like needles to reduce surface area
-densely packed mesophyll layer so water vapour cant go into these spaces (if it did more water would be needed) -thick waxy cuticle -hairs on surface that trap air and in turn the water vapour. this stops the plant from loosing water vapour as water potential is equal inside and outside -rolling of the leaves so the lower epidermis isnt exposed to the atmosphere, lowereing or even eliminating potential gradient |
