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Re: Faster growth in dim light stressful?

Greg wrote:
> It seems to me the plants grew faster during their dark period because
> they were looking for light.

Yes, but we shouldn't use anthropomorphic analogies too far. :-)

> The same chemicals that cause plants to lean or turn their leaves 
> toward light are at play.

I don't think the leaf turning mechanisms are growth related but I'm
very curious to learn more about how plants accomplish these feats.

> I suspect dormant Aponogetons, without leaves, wouldn't be able to 
> respond this way.

Without leaves, probably not. I saw no change in the A. mad. bulb without
any leaves. The other which has only small leaves and is very slow growing
did show a definite response and grew a single, much larger leaf (but
nowhere near the incredible size during the early active phase). This
leaf is about 4" x 1.5". I'd be surprised however if it continues to
grow actively now that the lights are back on but a period of reduced
lighting or lighting duration together with a reduced temperature to
about 65F for a few weeks followed by a temperature increase to 75F
might do the trick. Unfortunately, I cannot maintain a temperature lower
than about 70F in my apartment comfortably and the experiment with low
temperatures might have caused my previous ich outbreak. Perhaps this
spring might be the time to move the dormant bulbs to an outdoor
aquarium. I could manage it now if I put a heater in the outdoor tank
and used something to provide a little insulation. The stories about
surviving power outages provides interesting thoughts...

> My question: Is this good for the plants? Wouldn't subjecting them to dark
> periods now and then actually be stressful because it causes them to spurt
> in pursuit of light? I suppose once light is restored, the plant can build
> itself back up through photosynthesis.

My thinking is that it shouldn't be "stressful"; I think the growth
changes are natural responses of plants growing in a shady location
which grow taller in order to reach light. I suspect the change in
lighting condition produces a change in hormone levels which changes
the growth characteristics of the plants. Long term, one would
certainly expect to see the long leggy look. That kind of growth
pattern seems to be the situation where plants are grown continuously
in low light conditions.

> Is their growth in the dark leggy?

What I observed, no. The H poly in fact had short internode distances
and very small leaves. Others like Ludwigia were similar. The one with
the most distinguishable difference was the Lobelia which grew with
stems at about the normal configuration but the new leaves were very
much smaller. It is possible that all of these new leaves will now
reach normal size, or only the top few will continue to grow to
normal size. It does have a slightly leggy look to it compared to
normal but it's not unattractive (yet). Possibly, if the middle or
lower small leaves stay small, it might look a bit odd. A one day
dark, six day light regimen might be interesting to try.

Steve (glub-glub, darn rain; at least better than Seattle)