PLANT HISTORY CORRECTION

Mark J. Hovenden mark_jh at plant.utas.edu.au
Thu Oct 20 21:26:00 EST 1994


In article <01HIE1U6QOXU9D5UIB at mecn.mass.edu>, NEC95ISA09 at mecn.mass.edu
wrote:


> I am curious, primative plants, i.e., Liverworts, Hornworts and moss are
> considered to be distant ancestors to green algae.  I note that they are 

NO, sorry!  There is no possilibility that bryophytes are ancestral to
algae of any description.  Absolutely none.  Even the most complex algae
are more simple than any bryophyte (bryophytes are mosses, liverworts and
hornworts).

> "nonvascular plants" which mean they live in moist, shady areas.  In 

Sorry, wrong again.  Although many non-vascular plants do grow in
moist-shady environments, that doesn't mean that they are resticted to
them.  There are many, many species of bryophytes which live in deserts,
even polar deserts including Antarctica, my current field of interest.

...
 
> My question:  In the early stages of plant groups, was there, due to oxygen
> being less, a shortage of these plants.  Humans require 20% oxygen now due
> to events that have happened.  What specific amount of oxygen is required for
> plant life to survive?

I fail to see the relevance of oxygen abundance to the survival of
bryophytes.  Plants don't have anywhere near the same requirements for
oxygen as animals.  Indeed, RUBISCO, the most abundant and arguably the
most important protein in the world, works better at reduced concentrations
of O2.  I'm wouldn't be so brash as to say that plants will grow better at
reduced O2, although the Km for respiration is quite a bit lower than
current ambient levels.

Please outline the background to your thoughts so that we can discuss this
puzzling hypothesis!  It would probably be better discussed in
bionet.plants although you might get a few sarcastic responses. (OK, more
sarcastic than mine.)

Mark


Mark J. Hovenden                            mark_jh at plant.utas.edu.au
Dept. of Plant Science                      ph: +61 02 34 4973
University of Tasmania                          +61 02 20 2371
GPO Box 252C
Hobart TAS 7001
Australia



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