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Re:Weak Stems

    * From: Ed Dumas <a4a48835 at telus_net>
    * Date: Sun, 23 Dec 2001 20:13:37 -0800

I am seeing an unusual (?) growth pattern with some of my plants. The
side shoots of stem plants like Hygrophilia and Water Wisteria tend to
grow horizontally, and even seem to bend downwards as the plant
lengthens. I have also noticed that plants like Pennywort have rather
thin stems compared to the size of the leaves, or with specimens I have
seen available in stores.

I am wondering if this is a shortage of some nutrient, or if it is
because of not enough light. My 110 gallon tank certainly needs more
light, and may explain this, but it also seems to occur in the 10 gallon
tank which has 30 watts of screw-in compact flourescent at 6700 K. This
would make it in the 3 watts per gallon range, which I would think would
be sufficient.

It is not because of weak light or not enough nutrients; quite the
opposite.  It is because of good light and nutrients as well as good CO2
levels at least in the case of the Hygrophila and water wisteria.  I don't
know about the pennywort.  Is it spreading horizontally, also?  This is a
take-over strategy of these plants.  When they have good light and room
they send horizontal shoots in all directions to claim as much territory as
possible.  The Water wisteria (Hygrophila difformis) is a little bit more
specialized than H polysperma because the horizontal stems are thinner than
the upright stem and have longer internodes and reduced leaves.  H.
polysperma horizontal stems look no different than the upright ones.  When
light is strong and there is room, H. polysperma puts nearly all its effort
into horizontal growth.  Horizontal stems are even more specialized in the
Potomagetons, and plants like Hydrilla and Limnophila aquatica.  Here, you
would call them runners.  They have pretty much lost their leaves, and they
often branch as they spread out from the upright part of the plant.  The
whole strategy is to take over as much square footage as possible when the
light is good.  These species of plants are probably pioneer species.  They
are preparing for turf battles (pun intended).  Other species are going to
come in, and those who get there first claim as much turf as they can.

Paul Krombholz, in well-watered central Mississippi expecting to drop below
freezing tonight.