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

> >  As I am sitting here in front of my tank w. the lights
off (it's about
> > 11pm)

Why do you have lights off at 11 pm if you're not asleep?

> > I see all of the stem plants with their leaves raised -
> > they've closed shop for the night. ...

That is called Nyctinasty ( a rythmic diurnal movement).

> > I've seen this in terrestrial flowers, but don't really
notice it in
> > terrestrial plants.

Actually quite alot of terrestrial plants 'close shop' for
the night. Many leguminous plants close their leaves at
night, eg clover, acacia, mimosa and Phaseolus (beans). We
have alot of cape sorrel here, Oxalis, which fold up their
leaves, and if you try growing Marselia out of the water you
will see it do the the same thing daily.

> >  I am wondering why the aquatic stem plants do this.

First of all why do land plants do this? To conserve water
and heat is the usual textbook answer. Why do aquatic stem
plants do this? Many of these plants are not truly aquatic,
yet their behaviour continues underwater. So the answer is
the same as for terrestrial plants. What is interesting is
why truly aquatic plants (eg Tiger lotus ) also lift up
their leaves during the night? I think it also serves as a
defensive mechanism against herbivores, by protecting the
inner growing points. You may think of other defensive

> >  I'd think they'd stay open so that they can re-absorb
> >  O2, that is trapped under the leaves, for respiration.

They don't need that much oxygen.

> Jason - I don't have the answer to your question, but I've
noticed the same
> phenomena *before* lights out towards the end of the
lighting day, when the
> plants are really pearling.

Many nyctinastic movements continue even if the lights are
left on. 'There seems to be some inherent periodicity to the
movements". I think it is  like us getting sleepy, the time
not the light controls our sleepiness.

I hope that helps.


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