In message , Kay
writes
In article , datsy
writes


I've just done a Google image search on Aloe Vera and the images that came
up included varieties which had the broad leaves and ones with long spikes
at 90 deg. The image which seems to resemble mine is this one:
http://davarree.free.fr/Aloe.Vera.JPG

I've also had a look in the book mentioned above for other possibilities to
get oxygen at night in my north-facing bedroom - seems as though the snake
plant might be the one.

Aren't there lots of possibilities? Isn't this to do with crassulacean
acid metabolism (because it was first discovered in the crassulas)
whereby a great many plants in arid regions have adopted a metabolism
that allows them to do their photosynthesis in effect at night, so they
can shut down their stomata during the day and avoid losing water? It's
a long, long time since I read about this.

Yes. Thats the one. Many plants from arid climates have CAM to minimise
water loss. They only open the stomata at night. And make exotic
photosynthesis intermediates in sunlight completing the cycle at night
by grabbing more CO2 and emitting oxygen waste products.

However, it does require that they see enough strong sunlight to make a
decent amount of growth and oxygen. Otherwise they are budget neutral.

Regards,
--
Martin Brown