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04-03-2003, 08:22 AM

(Nick Maclaren) wrote in message ...
In article ,
(Jaak Suurpere) writes:
|
| It follows that many plants now growing in Azizija, or their
| ancestors, have heated to 58 degrees and lived. Actually, sunlit
| ground and plants on it could heat to higher temperatures than air in
| shadow!

They do, as I can witness. Thermophilic bacteria can take much
higher temperatures, too.

| It would seem likely that plants which can endure 58 degrees and low
| humidity could also endure 58 degrees and high humidity.

Not so. Inter alia, high humidity permits fungi to flourish.

At which temperatures?

Jakarta, one of the best-known places in humid tropics, has absolute
maximum of 37 degrees. We can fairly guess that some parts of humid
tropics would have absolute maxima a bit higher. But how much heat can
live fungi endure?

Few USA plants would last a month in the humid tropics, and none from
outside the deep south would. But there would be plants that could
adapt, given long enough.

| Now, the area with currently the highest dewpoint temperatures -
| southern Red Sea region - does not really have that great absolute
| temperature maxima. What makes the heat troublesome for men - not
| intolerable, since they do live there, and long have - is the fact
| that there are consistent high temperatures with high humidity.

Fairly high. Not very high. Nowhere near the tropical jungles.

| Now try to imagine a region where night temperatures are in lower 40-s
| and day temperatures in upper 40-s, with high humidity. Occasional
| maxima might be somewhere in 50-s, with high humidity...
|
| Men would not endure. On the other hand, many plants might.

It is unclear, given enough water. I don't know whether mammals'
requirements are for a bound on the relative humidity dependent
on temperature, or for a margin in water vapour pressure between
ambient and maximal (i.e. dew point).

If the latter, mammals would survive. And we are fairly typical
in this respect.

| Not all the plants, though. I wonder which plants would choose to grow
| in such conditions?

Nothing current, but some of them could adapt.

Really?
What I suppose is that there are plants which are preadapted. For
example, desert plants are adapted to great heat with low humidity.
Some of them might flourish with great heat and humidity.
I suppose that some fungi adapted to great humidity and moderate heat
might not be troubling with great heat. Of course, others might be
trouble.

Then again, if there are places with wet conditions, some plants
adapted to wet conditions and moderate heat might make do with wet
conditions and great heat - and be well rid of some of their
competitors as well as some herbivores.

| One more thing: these conditions might be unfavourable to many
| animals, including herbivores.

Yes, they would be.