Alan Meyer wrote:
I agree with the various critiques of the Aluminum Sequin proposal.
It's doomed from all points of view - practicality, effectiveness, and
political impossibility.

Then again, maybe it's not so politically impossible. Perhaps the
administrations that gave us Star Wars would find something like
this very much to their taste

But all that aside, I wonder if anyone has an answer to AP's
specific question?


Anyone know what the mechanism as to why plants would stop
growing with increasing Global Warming and increasing CO2??


Clearly, increasing CO2 will only increase photosynthetic rates to the
extent that they are limited by CO2 rather than other factors. Does anyone
know if currently available quantities of CO2 are a limiting factor? I
wouldn't think they pose a limit currently.

Temperature is also a factor, but global warming may have both positive
and negative effects on total plant growth. Warming may increase
photosynthetic activity in areas of the globe that are currently too cold
for part or all of the year, but may desertify other areas, reducing total
plant life in those areas.

But, as another poster pointed out, it's probably the effects in the
ocean that will be most telling.

Alan



Hiya,

A number of CO2-enrichment studies (eg. Gleadow et al 1998 - Plant, Cell
& Environment) show that plants (although it depends on the exact
species) can increase biomass in elevated CO2 - in the case of Gleadow,
Eucalyptus cladocalyx doubled it's biomass... but that was only over 6
months. A number of other studies (can't remember exact references) tend
to show a roughly equal short-term increase, followed by a reduction in
rate caused by down-regulation by the plant, usually in the form of
decreasing Rubisco concentration, as the accumulation of non-structural
carbohydrate in the leaves can cause damage. Also, the plant has better
stuff to do with it's nitrogen than make Rubisco, if it's getting enough
carbohydrate to satisfy it's growth requirements . Andf, of course,
Rubisco is more efficient in elevated CO2 anyway (as the oxygenase
reaction is inhibited).

So at the moment, it does seem that CO2 is the major limiting factor, in
terms of photosynthesis. It does have a number of other effects, though
- usually, the stomata of the plants remain closed for longer periods
than at ambient CO2, reducing water loss (and therefore increasing WUE)
-- meaning most plants will become more drought-hardy.

As the changes will proportionally benefit C3 plants over C4, there'll
be a number of interesting competitive effects, too.

Also, another study by Gleadow showed that the severity of frost damage
may be increased under elevated CO2 conditions...

xF,

....Nick

Oh, forgot to say... I'm a new poster . Bit of a daft introduction;
I'm just a boring biology undergraduate in Yorkshire, UK. Had to do a
presentation on this topic yesterday, believe it or not.