Definition of Plant

Bill Purves purves at THUBAN.AC.HMC.EDU
Fri Oct 8 13:22:40 EST 1999


Following up a bit on Ross's two good messages:

I'm underqualified to be guessing, but I'll guess anyhow and
predict that agreement among most players will be reached,
in a few years, on a proposition that divides the "protists"
into several kingdoms, based on phylogenetic arguments.

At the recent International Botanical Congress, press releases
were generated with a lot of new and quite old information.
One piece that struck me was mention of three "plant kingdoms":
"green plants," "brown plants," and "red plants."  The greens
would be the Chlorophyta-plus-land-plants.  Fine. The browns would include
the brown algae (Phaeophyta), diatoms, and golden algae, making an
ugly kingdom in phylogenetic terms, since evidence indicates that the
(kingdom?) Stramenopila is a monophyletic lineage that includes the
Bacillariophyta (diatoms), Chrysophyta (golden algae), Phaeophyta,
AND the Oomycota (water molds and powdery mildews).  The
red plants would be a clean, monophyletic kingdom consisting
of the red algae (Rhodophyta).

For our plant-edly purposes, each of us simply needs to decide
what works best in our own teaching.  One can opt for something
that tries very hard to represent true phylogeny (as far as
the evidence currently goes), or for something that makes sense
to an instructor in terms of ease or utility for the student,
or for something that matches whatever textbook is being used
(to minimize student confusion), or whatever.  As far as I
can tell, the organisms themselves don't care too much ;-)
My own current preference is for a phylogenetic approach.

(bill)


William K. Purves      Vice President/Editorial Director
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