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Dear Ted and Ken,
Thanks for this most interesting discussion. When I read the part of Ted`s
note describing the burning of the candles to reduce oxygen and so increase
the co2, I had exactly the same train of thought as Ken did---OK, oxygen is
reduced, but what about the by-products created by the burning candle in
such a sealed enviroment, i.e. the carbon, the fumes from burning petroleum
'wax', etc. I thought this akin to a badly functioning space heater in an
orchid house, the fumes kill the orchids but the owner is puzzled as he was,
after all, keeping the plants nice and warm. Perhaps the by-products from
the burning candle were responsible for the negative growth of Ted`s
plants?? Dry Ice might be a better way of increasing co2 to a closed
space, I have no proof of this. I know that my friend Bob who grows
fantastic aquarium plants does inject co2 into his aquariums water and
swears that it does wonders for his plant growth, I have no facts and
figures to back up his opinion though.
Nice discussion!
Cheers,
Julius
Ted,
>
>I love getting emails from people who can actually think critically. I
wish I had information to give you, but all I can say is that I applaud your
experiments. I wonder if burning the candle was a good way to increase co2?
The byproduct of burning candle wax would be co2, water and a bunch of other
stuff like sulphur compounds, etc. I wonder if any of those other chemicals
released into your enclosed environment were detrimental to your plants...
>
>If my Dad weren't retired from Pfizer I'd ask him to bring home chunks
of dry ice for me, surely the best way to introduce pure co2 into a small
volume - of course I couldn't do the calculations to determine just how much
I'd be adding!
>
>-Ken Mosher
> ----- Original Message -----
> From: Ted.Held@hstna.com
> To: Discussion of aroids
> Sent: Thursday, December 30, 2004 9:20 AM
> Subject: [Aroid-l] An Opinion on CO2 Injection
>
>
>
> This is in reply to the recent suggestion of CO2 injection to boost
aroid growth. This technique has been touted by some in the aquarium plant
hobby as the perfect remedy for weak plants. There is an impulse here from
the manufacturers of these systems, which are fairly expensive, and the
hobby literature contains many anecdotes endorsing the idea. I have never
installed one in my setup, so I cannot attest to the efficacy of such
equipment.
>
> But since I do specialize in aquatic plants, I have been interested
in these reports. The problem I have is that CO2 is not actually very
soluble in water. A few parts per million is a lot for water at the typical
pH 5 to 8 that is recommended for water plants. The lower the pH, the less
soluble CO2 will be. At pH 5, the solubility of CO2 will be essentially nil.
What happens, therefore, is that the excess gas "spills" to the
atmosphere as bubbles. There are those in the hobby that interpret the Pepsi
Cola-like effervescence and numerous attached subsurface bubbles as the huge
amount of oxygen generated by all the enhanced photosynthesis taking place.
This is humbug. The bubbles are just wasted CO2.
>
> Since I grow many of my water plants "emersed" (i.e. the
roots are submerged, but the leaves extend up into the air), I thought I
could test this elevated CO2 idea by pumping the airspace above the plants
with CO2. It turns out that this is a much more effective way of applying
CO2 than in the dissolved form since one can basically create a 5% CO2
concentration in the atmosphere and the amount of exposure there is many
times higher than what can be forced with dissolved CO2. My technique was to
simply burn a candle in the closed space above the water. When the oxygen
concentration goes from the normal 20% to 15% because of combustion, the
candle is extinguished. I found that my oxygen level returned to
approximately normal after 24 hours, at which point the candle would be lit
anew. The short version of the story is that I observed no increase in plant
growth or flowering in the 10 weeks that this regimen was in place. In fact,
I e nded the experiment when several of the plants exhibited evidence of
reduced growth. I concluded that the effect of increased CO2 is not nearly
so giddy as the injection people have maintained.
>
> One possible explanation for the results reported by partisans of
injection is that water (and air, for emersed plants) circulation is a
definite help in the growth of water plants (as, for example, Cryptocoryne,
an aroid genus of the Asian tropics). Perhaps the addition of injection
resulted in better circulation where a particular grower previously had
none. On the other hand, maybe the exuberant reports are simply hype. Maybe
I will be attacked here for suggesting this dangerous, contrary opinion.
>
> My larger point is to enquire to this list about any scientific
studies on the effect of elevated CO2 (as in a greenhouse) on the growth of
aroids. I am pretty sure that such studies have taken place for various food
crops (tomatoes) and the effect has been investigated recently in connection
with the Global Warming business. My understanding is that some plants will
grow more rapidly with extra CO2 while others will not benefit. Does anyone
know of any studies, one way or another, with CO2 and aroids?
>
>
>------------------------------------------------------------------------------
>
>
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