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    (Original post by uer23)
    lol liar, you're earliest post was 2 days ago. :rofl:
    Nah man no way :shock: you probably mistook me for someone else.
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    (Original post by ibysaiyan)
    Nah man no way :shock: you probably mistook me for someone else.
    http://www.thestudentroom.co.uk/show...postcount=1343
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    Alright that wasn't much of help for the posters now or was it ? xD
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    (Original post by ibysaiyan)
    Okes:
    For cell elongation here is what happens:
    Photo-tropins which are found around the cell membrane get phosphorylated this causes the flow of auxins sideways the way is not understood fully but two possible scenarios are its either that the phosphorylation causes more photo-tropins to get collected on a particular site or they use more energy.As auxin (IAA)travels sideways they cause a series of changed to their target cell.They attach onto the receptors which causes an increase of H+ ions within the cell,this activates an enzyme which cuts right through the plasmodesmata which causes them to loosen.

    =} but in apical dominance auxins work the other way around: They inhibit terminal buds (lateral) so auxin conc. at the top is more and as you go down decreases more buds being inhibited at the top and less and less as you go downwards =}
    can you explain the highlighted in laymans terms, causes thats confused me even more, lol.

    also, dont you mean apical where you put lateral in brackets?

    the reason why im confused with apical dominance is because of this paragraph in the ocr revision guide:

    in many plants, side shoots do not grow if the main shoot is growing. however, if the bud at the tip of the main shoot (apical/termind bud) is removed, the the lateral buds will start growing. this effect may be caused by auxins produced by the apical bud inhibiting groth of lateral buds. removing the apical bud removes the source of the inhibiory auxin.

    the above sounds like a contradiction of the explanation of apical dominance though. because auxin doesnt seem to inhibit apical/terminal buds in the explanation, they only inhibit the lateral buds. yet, in apical dominance auxin inhibits the terminal/apical buds, and doesnt inhibit the lateral buds, hence, the christmas tree shape.

    if it werent for that darn paragraph in the revision guide, i think i'd understand apical dominance. im still very much confused on the cell elongation stuff though, if you can explain it a bit more simply, i'd appreciate it.
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    (Original post by ViolinGirl)
    Apical dominance refers to how the growth of the apical bud prevents the growth of lateral buds further down the stem. .
    if thats the case than why are we given the example of a christmas tree as an example of apical dominance?
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    (Original post by ACDC)
    can you explain the highlighted in laymans terms, causes thats confused me even more, lol.

    also, dont you mean apical where you put lateral in brackets?

    the reason why im confused with apical dominance is because of this paragraph in the ocr revision guide:

    in many plants, side shoots do not grow if the main shoot is growing. however, if the bud at the tip of the main shoot (apical/termind bud) is removed, the the lateral buds will start growing. this effect may be caused by auxins produced by the apical bud inhibiting groth of lateral buds. removing the apical bud removes the source of the inhibiory auxin.

    the above sounds like a contradiction of the explanation of apical dominance though. because auxin doesnt seem to inhibit apical/terminal buds in the explanation, they only inhibit the lateral buds. yet, in apical dominance auxin inhibits the terminal/apical buds, and doesnt inhibit the lateral buds, hence, the christmas tree shape.

    if it werent for that darn paragraph in the revision guide, i think i'd understand apical dominance. im still very much confused on the cell elongation stuff though, if you can explain it a bit more simply, i'd appreciate it.
    Oh yea sorry about that basically in this case the receptors are complementary to the auxin such that when auxin binds to these lateral buds it inhibits their growth.
    The bit which you marked simply tells us that if we cut the terminal bud from where auxin is made then there wont be any inhibition of lateral buds as 0 concentration of auxin hence you will get growth.Nah I was right about the lateral buds but was mis-typed about the terminal bud.
    Any clear? If not quote me back again.
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    (Original post by ACDC)
    if thats the case than why are we given the example of a christmas tree as an example of apical dominance?
    Because it shows perfect working of apical dominance. Check my previous post.
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    (Original post by ibysaiyan)
    The bit which you marked simply tells us that if we cut the terminal bud from where auxin is made then there wont be any inhibition of lateral buds as 0 concentration of auxin hence you will get growth.Nah I was right about the lateral buds but was mis-typed about the terminal bud.
    Any clear? If not quote me back again.
    so if the theory is that, where theres a lack of auxin thats where you will get growth (as auxin is a growth inhibitor) why are the lateral buds not growing in the paragprah that i typed from the book. why does it take the apical buds (where auxin is produced) to be removed before they grow? you see how that doesnt make sense with apical dominance either? as in apical dominance theres less auxin lower down, therefore growth, and more higher up therefore lack of growth. but i seem to be understanding that paragraph as saying apical bud grows cause of auxin/you've also got higher conc of auxin above, yet, apical bud still grows, and auxin inhibits/stops growth of lateral buds, until the apical bud is cut... this all seems to be contradicting apical dominance.
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    (Original post by ACDC)
    so if the theory is that, where theres a lack of auxin thats where you will get growth (as auxin is a growth inhibitor) why are the lateral buds not growing in the paragprah that i typed from the book. why does it take the apical buds (where auxin is produced) to be removed before they grow? you see how that doesnt make sense with apical dominance either? as in apical dominance theres less auxin lower down, therefore growth, and more higher up therefore lack of growth. but i seem to be understanding that paragraph as saying apical bud grows cause of auxin/you've also got higher conc of auxin above, yet, apical bud still grows, and auxin inhibits/stops growth of lateral buds, until the apical bud is cut... this all seems to be contradicting apical dominance.
    The moment they cut-off the terminal base auxin production is lost so.... no more inhibition of lateral buds occur but I see what you mean now that why it has a non-uniform growth of leaves(overall) still I think it might be due to these changes being irreversible ?
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    (Original post by ibysaiyan)
    The moment they cut-off the terminal base auxin production is lost so.... no more inhibition of lateral buds occur but I see what you mean now that why it has a non-uniform growth of leaves(overall) still I think it might be due to these changes being irreversible ?
    does it possibly have to something to do with receptor sites of auxin? as lateral buds have receptors for auxin, auxin is able to inhibit lateral buds. but apical buds dont have receptors for it (i have no idea if they do or not, im just speculating), so although they produce it the effect of auxins on the apical bud is not effective because of lack of receptors. but that still wouldnt explain how you get the triangle shape. because you basically need to get rid of the auxin for lateral growth, so unless, they cut off the apical bud each time, how would that happen?
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    (Original post by ACDC)
    does it possibly have to something to do with receptor sites of auxin? as lateral buds have receptors for auxin, auxin is able to inhibit lateral buds. but apical buds dont have receptors for it (i have no idea if they do or not, im just speculating), so although they produce it the effect of auxins on the apical bud is not effective because of lack of receptors. but that still wouldnt explain how you get the upside-down triangle shape. because you basically need to get rid of the auxin for lateral growth, so unless, they cut off the apical bud each time, how would that happen?
    Well you get the triangular shape by the differences of the auxin concentration but since the terminal bud has been detached the changes cant be reversed?
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    (Original post by ibysaiyan)
    Well you get the triangular shape by the differences of the auxin concentration but since the terminal bud has been detached the changes cant be reversed?
    so, triangular shape is caused by no auxin lower down right? than unless, you cut the apical tip than howelse can this xmas tree shape take form? because if the tip stays, auxin will still be transported downwards.

    and how come you dont get like a rectangle shape when the tip is removed as the auxin is made in the tip. no tip = no auxin. so why doesnt the top of the middle and top of the tree show lateral growth either?


    haha, sorry to be a pain, but the more i think about it the more questions are raised in my mind :o:
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    (Original post by ACDC)
    so, triangular shape is caused by no auxin lower down right? than unless, you cut the apical tip than howelse can this xmas tree shape take form? because if the tip stays, auxin will still be transported downwards.

    and how come you dont get like a rectangle shape when the tip is removed as the auxin is made in the tip. no tip = no auxin. so why doesnt the top of the middle and top of the tree show lateral growth either?


    haha, sorry to be a pain, but the more i think about it the more questions are raised in my mind :o:
    Oh could it be that the book is referring to the spraying of auxins? Sorry If I am not being much of a help here feel exhausted :/
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    (Original post by ibysaiyan)
    Oh could it be that the book is referring to the spraying of auxins? Sorry If I am not being much of a help here feel exhausted :/
    no it doesnt mention anything about spraying.

    its the ocr revision guide (the cover is purple and black), the plant responses stuff is on pgs 82 and 83.

    no worries, i think ive sorta figured it out as we've gone along. im still puzzled by my last two questions though.
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    (Original post by ACDC)
    no it doesnt mention anything about spraying.

    its the ocr revision guide (the cover is purple and black), the plant responses stuff is on pgs 82 and 83.

    no worries, i think ive sorta figured it out as we've gone along. im still puzzled by my last two questions though.
    which are __________ ?
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    (Original post by ibysaiyan)
    which are __________ ?
    post 1392
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    (Original post by ACDC)
    if thats the case than why are we given the example of a christmas tree as an example of apical dominance?
    Not been aware of this being given as an example. A christmas tree is showing how apical dominace works. The tip of the tree is cut to allow for the growth of side stems further down the shoot.
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    [QUOTE=ACDC]can you explain the highlighted in laymans terms, causes thats confused me even more, lol.

    also, dont you mean apical where you put lateral in brackets?

    the reason why im confused with apical dominance is because of this paragraph in the ocr revision guide:

    in many plants, side shoots do not grow if the main shoot is growing. however, if the bud at the tip of the main shoot (apical/termind bud) is removed, the the lateral buds will start growing. this effect may be caused by auxins produced by the apical bud inhibiting groth of lateral buds. removing the apical bud removes the source of the inhibiory auxin.

    QUOTE]

    The paragraph makes perfect sense.
    The shoot grows, means auxins are being produced in the apex, so the presence of auxins inhibits the growth of side stems.
    Shoot is cut, auxins are no longer produced at tip = no longer inhibit growth of stem= stems can grow!

    I shall try and explain the rest simply:

    Apical dominance is when the growth of the apical bud at tip of stem, inhibits the growth of lateral stems further down the shoot.

    This is because auxins are produced in shoot tip. Auxins are hormones that inhibit growth of lateral shoots. When the tip is cut off, the auxins are no longer produced, so there is nothing preventing the growth of the stems further down the shoot.

    There is really nothing more to it. You just need to know the evidence that can be used to prove this is the case-that auxins are the inhibitors and there are various bits of info that show this, but also that there are 2 other hormones involved- abscinsic acid and cytokinins.
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    (Original post by Remarqable M)
    pm your email and i'll send it to you
    Pm'd and patiently waiting
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    (Original post by ViolinGirl)
    Not been aware of this being given as an example. A christmas tree is showing how apical dominace works. The tip of the tree is cut to allow for the growth of side stems further down the shoot.
    oh right, so the xmas tree is not showing apical domimance, but instead, demonstrating how apical dominance works by doing the reverse of apical domiance?
 
 
 
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