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[APD] Re: Closing up for the night - or Nyctinasty

> Interesting.  What triggers this cycle if it's not light?

It is primarily light. Diurnal heat and humidity rythms also regulate the
movements in some plants. What I said in my previous post was "Many
nyctinastic movements continue even if the lights are left on. There seems
to be some inherent periodicity to the movements". The plant regulates
itself with the light and dark periods, much like we do, at least most of
us. We go to sleep when it is dark. But if someone leaves the lights on we
still feel sleepy when it is dark outside. We get accustomed to the pattern
and it takes awhile before we adjust to new sleeping/waking times. The same
happens to some of these plants. Once it gets into the pattern, it continues
even if the light-dark cycle  is changed. If this cycle remains the plant
will change too. This is not true of all species, but it explains the
behaviour of some nyctinastic plants.

 >I know that in animals various glands or parts of the brain control these
rhythms.  A couple weeks ago, I heard an NPR >story that told of recent
discoveries in animals that in addition to these, each organ has its own
'clock', though they didn't go >into what controls it, or even what that
'clock' is.  I assume there must be some biochemical change in the plant
that causes >the leaves to fold up - do we even know what triggers it or
what the actual chemical change is?

I don't know if any new discoveries have been made, but my test books (quite
old) don't pinpoint anything. Sorry.

> Next time I hear a plant described as a 'primitive' form of life, I'll
think twice :-)

I think its humans that think of other organisms as primitive. What would a
plant think about us? For one thing we have to look for food, the plant can
make its own. If you like the subject of 'plant behaviour' there was a good
documentary/book called,  ' the secret life of plants' by Sir David
Attenborough (1995), which I found very interesting.

> Terry in Arizona

best regards


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