plant transport questions
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- Created by: sarah
- Created on: 27-04-14 21:39
why do plants need a transport system?
every cell needs regular supply of water & nutrients, and diffusion through the epithelial cells is not sufficient for the hole cell
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in the cross section of a root, what is the order of cell types?
epidermis, cortex, endermis, pericycle (meristem), vascular bundle
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how is the phloem and xylem arranged in the root?
xylem vescules are in a cross shape and phloem surround it
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in a cross section f a stem, what is the arrangement of cell types?
epidermis cells line the outside, then the cortex, the vascular bundles are in circular shapes around the outsides
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what is the arangement of cells in the vascular bundles in the stems
the xylem on the side closet to the center of the stem and then cambium (meristem), and then phloem, and then other cells (sclerenchyma)
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what is the arrangement of cells in the midriff of a leaf?
epidermis on the outside, mesophyll, vascular bundle in center
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how are the phloem and xylem vessels arranged in the vascular bundle in a leaf
xylem above phloem
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what is the difference between dicotyledon and monocotyledon leaves?
patterns of veins on leaf
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what are the layers of a leaf?
waxy cuticle, upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis (and guard cells)
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how is the leaf adapted to its function?
thick waxy cuticle (protection and reduces water loss), clear upper epidermis (let light through), palisade layer has lots of chloroplast, spongy mesophyl layer has air spaces to allow transport of gas,
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how are stomata adapted for their fuction
under leaf (avoid water loss), close at night (avoid water loss), gurad cells have thickend innor wall (made of spiral cellulose) so when water makes it turgid it opens gap
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why do plants need water?
tocarry minerals, to keep plant cells turgid (structure), keep plant cool (evaporation), photosynthesis, elongation of cells
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what is the equation for photosynthesis?
carbon dioxide + water = glucose and Oxygen
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why does water move into a cell?
because the cell has a lower water potential then the outside of the cell
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what is the term for higher water potential?
Hypotonic
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what is the name for lower water potential (more solutes)?
Hypertonic
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why do plant cells not burst?
cells have a cell wall keeping its shape, witch means as water enters the cell it increases pressure in cell, and so net movement into the cell will be less
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what happens to a cell when surrounded by low water potential?
there is a net movement of water out of the cell, and so cytoplasm shrinks and cell becomes flacid. if water potential gradient is significant, the cell membrane may pull away from the wall (plasmolysis)
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how does water enter a root hair cell?
minerol ions are activly transported into the root hair, reducing its water potential, this allows water to be transported in by osmosis
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how does water move along root hair cell?
minerals are activly transported ahead reducing water potential allowing solutions to travel aplast pathway (through cell wall) or symplast pathway travelling through plasmdesmata
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what happens at the endermis in a root
casparian ***** in cell walls (water proof - made of suberin) blocks aplast pathway forcing solution through membrane helping to direct it and reduce spread of infection
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how is the xylem adapted to its function?
narrow (continuous flow, does not break), pits (where lignification is not complete and allows horizontal movement of water), dead cells, end walls and content decay. lygin (waterproof + structure)
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how does lygin help the xylem vessel?
spiral pattern allows movement. waterproof and structure
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what is the term used for the attraction between the water and the sides of the xylem
Adhesion
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what is the cohesion tension theory
water molecules stick together due to week hydrogen bonds forming and braking, allowing water to be pulled up
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what is transpiration pull
the loss of water through the evaporation and diffustion through stomata, puts pressure on xylem causing root pressure and pulling water up stem
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what factors increase transpiration rate?
many large stomata, high winds (moves water vapor away from stomata increasing diffusion gradient), light (opens stomata), number of leaves (increased surface area), temperature (more evaporation, more kinetic energy, decreased water vapor potential)
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what factors decrease water potential
thick waxy cuticle, high humidity (reduces water vapor potential gradient), low water availability (stomata close, less water to replace loss)
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what is the name for organisms witch are adapted to extreme hot conditions?
Xerophytes
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how are some plants adapted to reduce water loss?
thick waxy cuticle, densely packed mesophyle (less air spaces for evaporation), hairs to trap air, pits to trap air, salt in leaves to reduce gradient, rollled leaves
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what is the word for the movement of sugar and minerals around the plant?
translocation
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what does the phloem transport?
disolved sugars and minerols
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what is the name of the cells attached to sieve tubes?
companion cells
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how does sugar enter phloem?
H+ ions are actively transported out of the companion cells (using ATP), co-transporter protiens are used to allow the H+ and sucrose back into companion cells. the sucrose can then diffuse into the sieve tissue through the plasmodesmata
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how does sucrose move to where its needed?
when it difuses into the phloem, it lowers its water potential, this causes more water to enter via osmosis, increasing hydrostatic pressure, moving it to where pressure is least (area with less sucrose)
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what are the features of phloem vessels?
stacked sieve tubes, thin walls, porous cross walls (sieve plates), little cytoplasm, no nucleus, companion cells
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in the summer where is the source and sink of sugar in plants?
leaves (made in leaves by photosynthesis) are source, roots are sink ( stored as starch)
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in the spring where is the source and sink of sugar in plants?
leaves are sink (sugar is needed for growth and respiration), root is source (stored carbohydrates are used)
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how do we know there is translocation?
ringing a tree (removing phloem at that point) causes sugar to build up above or bellow, causing a bulge. radioactive tag can tracesolution, aphid collect from plant
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how do we know plants need energy?
the rate of flow is too high, poisen that inhibits ATP production stops translocation, companion cells have lots of mitochondria
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what is the endodermis layer surrounding xylem in the root also known as?
starch seath
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how do we measure the rate of transpiration?
potometer measures rate of water uptacke by cut shoot (water lossed by leaf is replaced by water in tube, movement of meniscus at the end can be measured)
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what happens to sucrose at the sink?
it move into surrounding cells by active transport or diffusion, increasing water potential in that area, causing water to leave the element, reducing hydrostatic pressure
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Other cards in this set
Card 2
Front
in the cross section of a root, what is the order of cell types?
Back
epidermis, cortex, endermis, pericycle (meristem), vascular bundle
Card 3
Front
how is the phloem and xylem arranged in the root?
Back
Card 4
Front
in a cross section f a stem, what is the arrangement of cell types?
Back
Card 5
Front
what is the arangement of cells in the vascular bundles in the stems
Back
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