RE: Long internodes

["Karpa-Wilson, Douglas" <dkarpawi at indiana_edu>]

On Sept. 9 Rachel wrote:
> I have noticed that many of the fine-leaved plants in my tank - the purple
> cabomba, foxtail, and ambulia - do not look like the beautiful pictures in
> the Tepoot book. His are compact, lush, and bushy. Mine are growing
> quickly and are brightly colored, but the internodes are very long, so the > plants are not very good looking.


The traditional take on this would be that it may not be the total amount of light, but rather the spectrum of light they're getting.  Are these plants more or less by themselves, or do they have other tall plants growing alongside them?  In the generic plant physiology literature, this sounds a bit like the response to low red:far red ratios, which would result from shading, far red reflection from neighbors, or potentially from the type of bulbs in use (although as I recall, most fluorescents peak in the red, not far red, but I could be quite wrong about that).  Elongation responses, at least in terrestrial plants, key in on the ratio of red to far red, rather than the total amount of light, so that may be what's going on, although being underwater may well shift what ratios these plants are using as a cue for competition.  Folks with more aquatic specific knowledge might have something useful to see.

Doug