At 1:39 AM -0400 4/23/97, Joseph.Holtum wrote:
>Re Ross Koning's statement on the speed of growth by CAM plants:
>>The growth of CAM plants that take their CO2 in solely during the night
>(i.e. are operating solely in a CAM mode) is limited by the size of the
>vacuole (into which they stuff the malic acid) and the concentration
>gradient against which they can pump malic acid.
>>However, in the presence of water, many CAM plants open their stomata during
>the afternoon and fix CO2 via rubisco (i.e. normal C3 metabolism). Therefore
>they can grow at very good rates. I cant remember the numbers, but there are
>some very high growth rates recorded for CAM species (try Barry Osmonds 1978
>review in Ann reviews of Plant Physiol)
Indeed plants that are facultative have additional growth
rate advantages depending on conditions (another example of
why diversity and versatility are desirable characteristics).
To the extent that the least costly pathway (C-3) is used
the growth rate can be stimulated above obligate CAM species.
>what came first the chicken or the egg?
This is one of those questions I love to answer in my
classes. It is obviously the egg. Before a chicken
ever evolved, its non-chicken ancestor (perhaps a dinosaur)
reproduced via eggs. The egg evolved before there was
a chicken...or even any bird!
ross
_______________________________________________________________
Ross Koning | koning at ecsu.ctstateu.edu
Biology Department | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA | fax: 860-465-4479
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