Why do the auxins move away from the light?

Question

Why do the auxins move away from the light?

Answer 1

I'm not a biologist and this isn't my field. So there may be newer information related to your question.

Basically, there have been several hypotheses about the mechanism by which light and auxin interact in a plant to produce phototropism.

1. Light causes auxin (indole acetic acid) to move toward the dark side (away from the light).

2. Light causes an increased resistance to downward movement of auxin from the tip where it is produced. So more auxin moves down on the dark side.

3. Light impedes the production of auxin on the lighted side. So more auxin is produced on the dark side.

4. Light destroys (or degrades) some auxin on the lighted side, directly or indirectly.

5. Light reduces the response of growing cells to auxin.

Experiments by dela Fuente and Leopold published in 1968 support the first hypothesis and somewhat support the second hypothesis. They used indole acetic acid labeled with radioactive carbon to measure the lateral transport of auxin. They observed decreased lateral transport toward the light and increased lateral transport toward the dark. (See the pdf file in the links below; the paper is just over five pages long.)

If in fact a light-stimulated net lateral movement of auxin toward the dark side is primarily responsible for phototropism, this still does not explain how the light affects the lateral movement. I don't know the answer to this question, but it is an excellent question.

Answer 2

The auxins themselves do not move away from light.  Auxins are plant hormones that lengthen the cells in one side of a plants stem.  This causes the stem to bend towards the side which has the shorter cells - ie towards the light.  The less sunlight auxin has shining on it, the longer it will make the cells on that side, and so the greater the stem's bend in the opposite direction - towards the light.

I hope that makes sense!  It's hard to explain without a picture

Answer 3

They grow towards the light not away from it. Check this out for more info

http://news.bio-medicine.org/biology-new...

I know it looks boring but it explains very well.

Hope tht helps :)