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Re:nutrient deficiency symptoms related to lighting.

Roger Miller wrote, Wed., Oct 1:

>....This was pretty much my best alternative theory:  the damage from oxygen
>(the toxin) mimics the symptoms of K (or maybe Mg) deficiency.  But then
>I can't really explain why the oxygen toxicity wasn't handled by the
>normal means.  Can you refresh my memory about what toxin mimiced [is
>that a word?] calcium deficiency?

I am almost sure that it isn't oxygen toxicity.  The only known form of
naturally occuring oxygen toxicity in plants is called photorespiration,
and it isn't a toxicity that damages the plant, rather it causes a
reduction in CO2 uptake because oxygen, at very high levels competes with
CO2 for uptake in the Calvin cycle.  The only effect is reduced CO2 uptake
and, thus, reduced photosynthesis rate.  Plants that often are exposed to
high levels of O2 and low levels of CO2 have evolved a way around this
problem callled the C4 pathway.  I would look for possibly a metal toxicity
or perhaps you have some kind of man-made organic polymer that may be
releasing a toxin.  The toxicity I had that mimicked (I looked that word up
in the dictionary) Calcium deficiency came from nylon cloth---a window
curtain material---I had used to make a Daphnia cage for keeping Daphnia in
a tank with fish.  Despite water changes, the material gave off for years a
toxin that stopped growth and, after several months, killed my plants.  See
TAG, V5, #3, pp 50-54 for a write up of this.

>...... I'll take the soil idea seriously.  It's
>something I've been wanting to test for a while now.

In spite of Dan Q's information about the amounts of iron in kittly litter,
I recommend the topsoil because of greater amounts and kinds of organic
matter in it.  In addition topsoil has a great variety of bacteria, many of
which are facultative anaerobes and can quickly adapt to low oxygen levels
and can reduce ferric (oxidized) iron to the more soluble ferrous forms.  I
recall you said you had gravel with no additions other than accumulated
mulm, and that makes me think of iron deficiency, even though the symptoms
don't resemble iron deficiency.  I have worked with topsoil for a long
time, and if the H corymbosa still shows the same symptoms after growing in
a pot of it, I believe we can narrow down the possible causes.

Having lived in rainier parts of the country, I hadn't considered the
alkaline desert soils.   I think I read somewhere that the primary
contributor to the alkalinity is sodium bicarbonate.  If that is so, it
should be possible to leach it out with rain water, deionized water, etc.
You mentioned some other kinds of soils---a river bank soil and a black
muck.  The river bank soil might not have very much organic matter in it,
and the black muck may not have very much iron in it, or any mineral soil,
for that matter.  It might be interesting to make a mixture of the two.
However,I would worry a bit about introducing unwelcome species of hair
algae with any soils that come from locations near water.

Paul Krombholz in Jackson, Mississippi with typical dry, warm, October