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What is nastic movement due to growth?

  1. Aug 14, 2016 #1
    I have read in my biology book that "nastic movement is the movement that occur due to difference in the rate of growth on two opposite sides of a plant organ" , but I can't visualize how this movement take place and how the rate of growth cause this movement?
     
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  3. Aug 14, 2016 #2

    jim mcnamara

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    nastic movement: As an example, plant grows sideways toward a light source on the side, move the light source and subsequent growth is toward the light.
    How this works: put your hands together, matching fingers on the right with fingers on the left. Push together lightly at the fingetips. Move your left hand up.
    You are making the left fingers "longer" than the right fingers. Keep fingers in contact at the palp. Then note. Fingers on the right hand flex away from the left, the left fingers flex toward the right. Voila! nastic movement.
    The side with "longer" fingers (or cells) dictates a change in direction.

    This response (making the cells on the side away from light source grow longer )is mediated by plant hormones like indole acetic acid (an auxin), to make the plant grow toward light.

    This movement can happen on the order of hours. Sunflowers are a great example - read and see the video:
    http://www.npr.org/sections/thetwo-...-why-sunflowers-turn-to-follow-the-sun-solved
     
  4. Aug 14, 2016 #3

    phinds

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    @jim mcnamara your explanation seems to contradict the Wikipedia entry. Is it wrong or am I missing something? Red bold is what I mean

    Nastic movements are non-directional responses to stimuli (e.g. temperature, humidity, light irradiance), and are usually associated with plants. The movement can be due to changes in turgor or changes in growth (therefore K+ ion concentration usually controls such movement in plants). Nastic movements differ from tropic movements in that the direction of tropic responses depends on the direction of the stimulus, whereas the direction of nastic movements is independent of the stimulus's position.
     
  5. Aug 14, 2016 #4

    jim mcnamara

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    @phinds - yeah, you can go that way. There are literally dozens of tropisms and nastic responses. Many have similar root names BTW.
    [opinion]
    The names are cubbyholes, not necessarily explanatory in anyway. The naming conventions date from the late1800's. AFAIK. This reference has all of them as of 1990 (I think).
    J.W. Hart , 1990 'Plant tropisms: and other plant movements' Springer
    IMO one of the main points in the book is what my point here is about definitions versus biological process. Most of these nastics and tropisms rely on similar cellular responses like osmotic changes and growth rate changes, mediated by 'plant hormones', another old term.
    I was taught that biological processes and metabolic pathways transcend cubbyhole definitions. I could definitely be wrong.
    I did have to regurgitate these terms on exams back in the early 1960's, so I am not glossing over them.
    And what the OP specifically asked was about changes in cell size to 'move'. A fair number of tropisms and nastics both use this identical trick.
    So I absolutely stand by the explanation, if not terminology.
    [/opinion]
     
  6. Aug 14, 2016 #5

    phinds

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    Sounds reasonable to me, particularly your comment "biological processes and metabolic pathways transcend cubbyhole definitions".

    I know nothing about the field so was just going by what I read. Thanks.
     
  7. Aug 14, 2016 #6

    jim mcnamara

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    @phinds Check out the sunflower video - really well done. Wish I had resources like that when I was teaching Freshman Botany years
     
  8. Aug 14, 2016 #7

    phinds

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    Yeah, that is cool. It does leave me with a question though. There is a statement in there that says the adult plants are warmer, the better to attract pollinators. Why would they be warmer that one that has its face towards the sun more?
     
  9. Aug 14, 2016 #8
    I have watched that clip in which sunflower is moving towards the side where sunlight is more. Now according to your explanation when rate of growth on one side increases then that side will move towards the opposite side. Right? If sunlight is reaching to sunflower from east on its left side of stem the cells on that side grow rapidly due to increase in concentration of auxin and it should move away from sunlight as you said in your reply.
     
  10. Aug 15, 2016 #9

    jim mcnamara

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    @Aafia - yes. You got it. And as phinds pointed out tropisms and nastic responses have different names. But they share similar processes.
     
  11. Aug 15, 2016 #10

    jim mcnamara

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    Woodworking note -
    @phinds - BTW This topic, differential growth induced by external stimulus, is also the reason for compression wood. Or why furniture made from branch wood tends to warp more than furniture wood from the vertical bole of the tree. The size and density of wood on the lower "half" of a branch has more but smaller xylem cells, with thicker cell walls. Slightly more dense wood. So the coefficient of expansion for moisture level change is different from upper to under. Coping with humidity induced expansion is bad enough with radial and tangential expansion, but imperceptible density changes across the board adds extra nastiness.
    See Hoadley's 'Understanding Wood' - a fantastic book IMO.

    In answer to your question there seems to be a bioenergetic answer: warmer nectar in the morning means more energy for the bee, less energy used by the bee to stay warm. Kinda like drinking hot chocolate to warm you up. The little animation did not mention 'in the morning', I guess you are supposed to figure that out on your own. Bees tend to go back to the flowers they visited earlier. Being the warmest flower and thus first visited in the morning, has advantages. More bees make return trips to that same flower.

    See: http://news.nationalgeographic.com/news/2006/08/060802-warm-flowers.html
     
  12. Aug 15, 2016 #11

    phinds

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  13. Aug 15, 2016 #12
    I am mistaken here
    Sunflower do not move away from sunlight rather it moves towards the sunlight because the illuminated side of sunflower has less concentration of auxin as compared to the side which is not illuminated with sunlight therefore it bends towards sunlight. Is that right?
     
  14. Aug 15, 2016 #13

    jim mcnamara

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    More auxin == more movement or growth. The side with more auxin bends away from the side with more auxin toward less auxin side. More cell elongation and growth on the "more auxin" side. And remember: movement toward -> tropism, other directions -> nastic. The sunflowers are showing phototropism but they use the exact same mechanism as does many nastic movements, so they are explanatory for any case like this.
     
  15. Aug 15, 2016 #14
    OK I got it now. Thank you for explaining. :oldsmile:
     
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