biology

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Martijn
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biology

Post by Martijn » Sun Sep 13, 2009 7:38 pm

There is no biology thread and as I have a biology related question, I thought I'd start one. I know about photosynthesis and how trees don't get enough sunlight (and water) in autumn and winter, so they withdraw the greenness from their leaves, which makes them turn brown. (Well, kind of like that.) However, there's a tree in front of our flat of which every autumn the leaves on one side turn brown/yellow/red a lot earlier than those on other sides. The strange thing is that this is the south side and, since we're north of the tropic of Cancer, this side gets most sunlight. I'm sure there's an easy explanation for this, but what?

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soft revolution
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Re: biology

Post by soft revolution » Sun Sep 13, 2009 9:47 pm

There's two trees outside my office window which change colour about a month apart, despite being next to each other, so there must be some other factor too. I've found this explaination. If it happens like that every year then it might be the roots or something?
And by me, I mean, Flexo.

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Big Nose
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Re: biology

Post by Big Nose » Mon Sep 14, 2009 9:19 pm

Martijn wrote:There is no biology thread and as I have a biology related question, I thought I'd start one. I know about photosynthesis and how trees don't get enough sunlight (and water) in autumn and winter, so they withdraw the greenness from their leaves, which makes them turn brown. (Well, kind of like that.) However, there's a tree in front of our flat of which every autumn the leaves on one side turn brown/yellow/red a lot earlier than those on other sides. The strange thing is that this is the south side and, since we're north of the tropic of Cancer, this side gets most sunlight. I'm sure there's an easy explanation for this, but what?
The leaves on the south side are the ones most packed out with chlorophyll which has been stored up during summer photosynthesis. I reckon when the tree decides its time to start munching down on its stores of chlorophyll it takes them from the leaves with the most stored energy first (just as humans put weight on/and take weight off first in certain regions etc..)

Observe that tree and see if, come springtime, the leaves on the south side green up before the others.

Or something.
My apple pies go off today.

Your Funny Uncle
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Re: biology

Post by Your Funny Uncle » Mon Sep 14, 2009 9:33 pm

I don't know quite why I find this so cool, but I love the fact that the colours we see in autumn leaves are in fact there all throughout their lives, but only appear clearly when the chlorohphyll (which makes all the green colour) is gone. Sorry I don't know the answer to your question, Martijn...

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Gordon
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Re: biology

Post by Gordon » Tue Sep 15, 2009 6:27 pm

Big Nose wrote:
Martijn wrote:There is no biology thread and as I have a biology related question, I thought I'd start one. I know about photosynthesis and how trees don't get enough sunlight (and water) in autumn and winter, so they withdraw the greenness from their leaves, which makes them turn brown. (Well, kind of like that.) However, there's a tree in front of our flat of which every autumn the leaves on one side turn brown/yellow/red a lot earlier than those on other sides. The strange thing is that this is the south side and, since we're north of the tropic of Cancer, this side gets most sunlight. I'm sure there's an easy explanation for this, but what?
The leaves on the south side are the ones most packed out with chlorophyll which has been stored up during summer photosynthesis. I reckon when the tree decides its time to start munching down on its stores of chlorophyll it takes them from the leaves with the most stored energy first (just as humans put weight on/and take weight off first in certain regions etc..)

Observe that tree and see if, come springtime, the leaves on the south side green up before the others.

Or something.
I'm pretty sure chlorophyll doesn't get stored up, but it's a while since my bio degree.
Toot toot.

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Big Nose
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Re: biology

Post by Big Nose » Tue Sep 15, 2009 6:43 pm

Gordon wrote:I'm pretty sure chlorophyll doesn't get stored up, but it's a while since my bio degree.
Most of my info comes straight out of the Ladybird Big Book of Science. I like the pictures.
My apple pies go off today.

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nanski
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Re: biology

Post by nanski » Tue Oct 27, 2009 12:44 pm

prepare yourselves for a rant.

so... back when i was young, and had a photographic memory... i had a biology teacher who made us do a collection of 100 leaves from our region (actually, we could do insects or small vertebrates, but frankly-- NO). so there was a time when i knew what 100 different leaves in Alabama look like.

And evidently, I still do! !!!! my sister and her family took a bunch of pictures of their hike in the NC mountains this weekend, and they were debating (via facebook) what the identity of this and that tree was, based on leaf pictures, and I'm all like "that's a tulip tree" and " well, i really can't tell from the picture but hickory trees have compound leaves. i think that's a chestnut oak" and "no way that's a sycamore"

where the f*ck does this come from?!?!?! and why can't i remember what happened yesterday if i can recall this nonsense?!?!?!

i f*cking hate my head sometimes!

/rant
big hole! big hole! big hole! big man! big man!

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Damian
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Re: biology

Post by Damian » Tue Oct 27, 2009 1:36 pm

I think Big Nose has probably got the answer here, the leaves change because of the breaking down of chlorophyll. This article is nice:-

http://www.accessexcellence.org/WN/SUA06/leaves.php

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nanski
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Re: biology

Post by nanski » Sat Oct 09, 2010 7:41 am

i really love this story. I hope they can find a cure.

http://www.nytimes.com/2010/10/07/scien ... ef=general
big hole! big hole! big hole! big man! big man!

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