Yep. Found that mine actually close up before lights out. It's like they're shutting up shop once they've done enough photosynthesising for the day!

 

L. Aromatica does the same thing along with many other plants.

 

my rotala rotundifolia and hygro polysperma also do this.

(in liu of actually getting a timer for my lights I now just turn them off once I see my plants start to close up.)

 

Most of my plants do it....


L.Aromatica
R.Rotundifolia
R.Najenshan
R.Colorata
R.Sp.Green
R.Wallichii
R.Sp.Vietnam

 

Yep! It's rather interesting, I have changed my photoperiod, and once accustomed, it seems they start closing up about 30-45 minutes prior to lights out once they've become accustomed to the photoperiod being used. Do any of the plant physiologists out there know if there's a name for this?

 

Nyctinasty is movement of a plant or plant part in response to the onset of darkness.

 

But in this case there was no onset of darkness prior to the the plant movement. When the plant started closing, the light was still on and as strong as usual.

 

But in this case there was no onset of darkness prior to the the plant movement.

The behavior described was near lights out.

Nyctinastic leaf movements are accomplished in plants by using circadian rhythms to measure day-length (see Photoperiodism). Chemicals are released (various, depending on the species) in response to photoperiodic effects to facilitate the movement of the leaf at the appropriate time.

A circadian rhythm is a roughly-24-hour cycle in the physiological processes of living beings,

Photoperiodism is the ability of plants to measure the length of periods of light.

 

I did a Google search on nyctinasty and found the following article:

http://www-saps.plantsci.cam.ac.uk/records/rec117.htm

It explains nyctinasty in terms of the cell level events triggered by the change of light. That is consistent with what you'd said earlier that nyctinasty is in response to the onset of darkness. The onset of darkness changes the light reaching a plant.

But what we have observed here happened before, not after, the change of light. There was no change-of-light as a trigger.

 

It explains nyctinasty in terms of the cell level events triggered by the change of light.

In the article you quoted the trigger was the change of light but this is not the only mechanism.
I have included the link for the earlier quotes.
http://database.biomimicry.org/item.php?id=1044&table=strategy
You might also perform a web search for "Nyctinastic leaf movement".
The circadian rhythmic leaf movement described is known as nyctinasty.

 

Wiste is right. The plants are closing up even before the lights dim, as they have had enough light and are closing up. Nyctinasty is not just caused by light levels dropping. As Wiste said it can be to do with the circadian rhythm of the plant where it starts to undergo 'night' behaviour once it has finished it's 'day' behavious of photosynthesising.

 

Circadian rhythm is just a characterization of the rhythmic repetition of certain phenomena in living organisms at about the same time each day. It postulates an internal body clock. But it does not actually explain things.

 

Wow, I stepped away for a few days and here are all these replies. Thanks folks! I have 4 T5 bulbs over my tank and two of them go off an hour earlier than the others. But as many of you have pointed out, the r. wallichii was closing up before any light change, and even with my old lighting set-up and off times.

My photoperiod is 12 hours, with all lights coming on at once in the (late) morning, and at night they turn off two at a time an hour apart as mentioned above. CO2 is constant 24/7. I add fertz in the morning before the lights come on.

I also have many other plants, some of which mentioned in your replies also close, but mine do not. For example, my r.rotundifolia stays the same all day long! Who knows . . .

 

It could be that the plants are picking up extra light from outside, and as the day nears the end, they are sensitive enough to pick up the change in light. But other than that maybe they're smart plants.

 

Interesting , the aquatic plants and all plants in whole need to sleep and the cycle of a plant is composed of 2 bigs parts.
When the plant take co2 for the photosynthese and the inverse during the night.
Either the plant have finished his photosynthese or the light period is too long. (about 12h for most of tropical plants)

 

If you give the plant constant light or constant darkness, the circadian rhythm continues with the opening and the closing of the leaves. However, without the light dark cues, the rhythm drifts away from the actual day-night cycle. When the day-night cycle is returned, the plant gets back in sync in a few days. The plant is 'jet lagged' until it gets back in sync.