fmaguire <fmaguire at indigo.ie> wrote in article
<5ffd15$k9d at news.indigo.ie>...
> It is a well known fact that plants are influenced by visible light.
>> If I plant a tray of seeds, I can watch the emerging seedlings follow
> the sun across the sky.
>> However, what puzzles me is this....When the seeds germinate underground
> (in the dark!), how do they know to grow upwards towards the sun?
>> Are they influenced by the earth's magnetic field, or by radiation
> the visible spectrum, or what?
>> Any ideas?
>I heard in my latest botany class that plants respond to gravity. To know
the details of this process, I'd have to look up my notes, but as far as I
remember, there are particles in the plant cell which gather on the
"bottom" of the cell and thus communicate to the plant which way is up.
Once it breaks through the earth, hormones dictate the growth direction. I
think I'll go and look it up, it's been a while.