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Re: interesting article
> > From: Lori (Fiesta Cranberry)
> > OK, so how does this translate to plant tanks?
David Youngker replied:
> All it's *really* pointing out is the effect of
> narrowing your research focus too much: to believe
> that the _obvious_ effects of global warming will
> be the _only_ factors affecting the outcome.
Well, yes, but I'd strip the word "_obvious_"
because more is going on here.
> I'm assuming that in this case, the researchers'
> interest in climatic events overshadowed their
> background knowledge in plant physiology.
These *are* phsiologists. They *do* know quite a
bit about these physiologic processes.
> Especially when you see quotes such as that in
> your copy of the article:
> Richard J. Norby, an environmental scientist at the
> Oak Ridge National Laboratory, said the Stanford
> study "is a surprise."
Um, I've got a lot of formal training here and
it's a surprise to me too.
> "We don't really understand the responses of the
> plants (in the study)," said Norby, who is doing
> similar research in his lab. "I think this
> challenges some of our assumptions about global
> climate change."
I don't understand the response either. It seems
plausible, but I can't explain it.
> I imagine there'll be a few other things to
> consider as well. For instance, as the climate
> warms the growing season will be extended. But the
> natural duration of illumination won't be changing
> along with it. This may well interfere with some
> of the reproductive triggers in temperate plants -
> those that are in an annual race to reproduce and
> bear fruit as the light fades and the temperature
> drops. But now the temperature might not be
> dropping as rapidly, and we all know that things
> happen at a faster pace with warmer temperatures.
> Will the plants now produce fuller, riper fruit?
> Or will they "burn out" at the increased pace
> before fruition? Here again, the plant may
> outstrip some available element - particularly
> phosphorus - and hit another limitation "wall".
> And this would affect "wild" stock more than
> cultivated stock, although there would be other
> things to consider with cash crops where things
> like fertilization timing might be affected.
Yes, you're right with suggesting "interference"
(not in the formal sense), but not for reproductive
success. We're simply talking about biomass
accumulation, which is the result of Net Primary
Productivity (NPP). A plant is able to fix so
much energy from the sun, (Gross Primary
Productivity), but like all living things plants
must use some of that energy at the cellular level
for active transport and other stuff (the plant
respires, giving off CO2 just like animals). A
"successful" plant will fix more energy than it
utilizes, so the total O2 output from photosynthesis
exceeds the total CO2 output from respiration, and
there is energy left over for biomass accumulation.
The clippings we have in our tanks are a direct
measure of the "net" result of this process, which
You are correct that "other factors" are worth
considering to affect NPP (of course... it's a big
and complicated system). The most astounding
conclusion from this article, IMHO, is that
one traditional systems research approach for
isolating deltas based on a single parameter may
not be suggestive of generalized system response
(we've been plotting on a two-dimensional graph,
when in fact, we needed to have a three dimensional
graph, but we've never measured the third dimension,
or in this case, we don't even know what the third
To some extent this is hardly a surprise: We still
have a hard time identifying whether "correlated"
effects are "causal" (add CO2 to the tank, plants
grow better: Is that because the plants needed the
CO2, or because the plants needed something we're
not measuring, and that other thing needed the CO2?
Can you get that other thing *without* CO2?)
Of course, we *know* plants fix carbon (we are
carbon based life forms), and we can even describe
that chemical reaction down to the electron.
However, it's a little surprising that this often
limiting nutrient that is chemically "safe" as
a fundamental Life Building Block on Earth (no
critter can possibly develop an allergic reaction
to carbon) is such a *huge* show stopper when
present in higher quantities, when it's usually
a limiting factor.
> But I digress from the original question.
> Wearing "blinders" is something we *all* do on
> occasion. Luckily, most of *us* (in the hobby) do
> it from simple lack of knowledge or experience.
> These poor folks (the researchers) seem to have
> spent a number of _years_ simply validating the
> concept of nutrient limitation - something
> understood for decades prior...
I think that's a little unfair. It's true they
wore "blinders" in the sense that scientific
experiments have control and test populations.
Why don't you have a control population for every
possible combination of every possible parameter?
In working with systems, that is impossible. In
this case, they are following the standard method
of isolating one variable at a time to track
that variable's contribution to plant growth.
Before the research, CO2 was "good" for plant growth.
After their research, CO2 might sometimes be a little
"good" (8%), and sometimes *very bad* (40% growth
penalty). That's legitimately a "surprise", unless
someone out there can show that this has been stated
somewhere through previous research (I've not seen
These researchers aren't stupid, nor careless, nor
ignorant. They are well versed in the literature,
and there's *nothing* out there to suggest what
they've found. Back to the original question,
applied to plant tanks, here's what their research
Run your tank at 68F. That's our baseline.
Now keep the tank at 68F. Add CO2. Plants grow
Take the temperature up to 74F. Add PMDD, but
get rid of the CO2. Plants now grow 84% faster.
Take the temperature up to 74F. Add PMDD, and
also add the CO2. Plants now grow 44% faster.
??WHAT?? You paid all that money for CO2, and
it KILLED your production by 40%, over NOT having
CO2? CO2 might be "good" at low temperatures, but
"harmful" at temperatures just a couple degrees
higher? What's going on? (This is *very* sensitive
cellular chemistry if it's affected by only one
or two degrees, when averaged over years.)
(Of course, their research was on 128 plots of
California grassland, not on aquatic plants.)
This amazing and profound to plant physiologists
(IMHO), because it's never been described before.
charleyb123 at yahoo_com
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