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quixoticgeek
Joined: 23 Dec 2008 Posts: 296 Location: Canterbury
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Treacodactyl Downsizer Moderator
Joined: 28 Oct 2004 Posts: 25795 Location: Jumping on the bandwagon of opportunism
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Slim
Joined: 05 Mar 2006 Posts: 6612 Location: New England (In the US of A)
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quixoticgeek
Joined: 23 Dec 2008 Posts: 296 Location: Canterbury
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Mistress Rose
Joined: 21 Jul 2011 Posts: 15966
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Slim
Joined: 05 Mar 2006 Posts: 6612 Location: New England (In the US of A)
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lorrayne
Joined: 17 Dec 2004 Posts: 239 Location: Hampshire
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Mistress Rose
Joined: 21 Jul 2011 Posts: 15966
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Nick
Joined: 02 Nov 2004 Posts: 34535 Location: Hereford
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chez
Joined: 13 Aug 2006 Posts: 35935 Location: The Hive of the Uberbee, Quantock Hills, Somerset
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Slim
Joined: 05 Mar 2006 Posts: 6612 Location: New England (In the US of A)
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Posted: Sun Jan 31, 16 12:24 pm Post subject: |
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Nick wrote: |
Mistress Rose wrote: |
Slim, if tops grow up, roots grow down, at what angle might need some experiment. I assumed it was the tops as that is the bit that would be seen. |
Gravitropism was pretty well understood by Darwin. Shoots grow directly away from gravity, roots towards it. So, theoretically, the centre of the earth. It's mediated by auxin, and can be complicated by competition with light sensitivity. |
The biggest effects we see are definitely gravitropism and phototropism. But it's of course always more complicated than that as well. For example, when a root hits a rock and starts to curve to one side, that physical stretching of the outside of the curve spurs on a lateral root branch being initiated so the roots starts to grow in either direction around the rock.
Auxin is the big player, but there are a whole suite of plant hormones that are doing things and having effects. Strigalactones are a newly discovered class of plant hormones that seem to being involved in more and more aspects of plant development. (often in concert with auxin) |
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