Re: Hygrophila polysperma

>From: RevWCw at aol_com
>Date: Wed, 23 Oct 1996 09:48:23 -0400

>I have noticed that the leaves of h. polysperma sometimes turn upward, almost
>closing at the top of the stem.  Other times they are flat, extending
>straight out from the stem.  Still other times, they are turned down.  This
>does not seem to be strictly related to the light.  What does this mean?  Is
>this an indication of water condition?
H. polysperma and many other plants have "sleep" movements that are based
on a circadian rhythm (internal clock).  The leaves near the growing tip
begin to close about an hour before the lights are due to be turned off.
They begin to open before the light goes on in the morning.  I have seen H.
polysperma leaves slant down in upright plants only when other plants which
are able to utilize bicarbonate have lowered the CO2 content to the point
where the H. polysperma can not grow at all.  The leaves also slant back on
horizontal stems especially when conditions are good and the plants are
growing very rapidly.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174
In cool Mississippi, where we finally got some rain.