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Re: Folding Leaves



Dan wrote:

Is there any benefit to matching photoperiod to the folding of plants'
leaves? Some of my plants (e.g., rotala wallichii) are folding up before

lights go off. Is this depriving the plants of anything, or does the
folding
regulate the plants' biological processes regardless?

Dan,

I have been thinking about the phenomenon of leaf movement as I recently
added some red Cabomba to my tank and it is out of synch with the other
plants that fold their leaves.  So I dragged out my plant physiology
textbook and re-read the chapter on biological clocks.  This Circadian
rhythm we witness every night (photoperiod refers to flowering in
response to day length) is in response to an internal clock mechanism, a
photoreceptor pigment complex that is sensitive to light, notably,
far-red and red light.

When plants are exposed to an oscillating light environment, and they
exhibit the same rhythm, they are said to be entrained to the
environment.  Obviously my Cabomba has not been entrained to the light
rhythm of my tank.  Fortunately this rhythm can be re-set.  A flash of
light after lights out can delay the rhythm.  It is as though the flash
of light were acting as dusk, but by coming later it causes a delay.  As
the flash of light is given later and later during the night, the extent
of the delay is increased, to a point where a flash of light suddenly
results in an advance of the rhythm acting as dawn rather than dusk.

Light from a window or a lamp may also re-synchronize the rhythm,
delaying or advancing it, depending on when it occurs during the dark
period.  I havenít yet tried to re-set the rhythm of any of my plants,
as I donít have total control of the extraneous light sources.  Changing
when your lights go on to coordinate with the circadian rhythm of your
plants may benefit them as they may be ready to start metabolizing
sooner than when your lights come on now, thereby giving them more time
to photosynthesize.

I hope this helps!

Gilbert Martinez