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Plants and Algae

charles francis delwiche cdelwich at nickel.ucs.indiana.edu
Mon Aug 23 10:32:47 EST 1993

In <01H1Z1YY0ZPI9I449V at Butler.EDU> SCHMID at Butler.EDU writes:

>"Algae are plants" is a controversial statement.  In the days when all life
>forms were classified as plants or animals, there was no problem.  However,
>even general biology texts these days reveal little agreement on algae. 
>Modifications of Whittaker's 5-kingdom scheme all place blue-green algae
>(aka cyanobacteria) in Kingdom Monera with the prokaryotes.  The other,
>eukaryotic algae may be lumped into Kingdom Protista/Protoctista -- or
>split between Protista and the Plant Kingdom.   Many scientists argue that
>the algae are polyphyletic - having obtained chloroplasts in independent
>events - suggesting that not all are closely related to land plants.

>Moral for Physiologists:  Don't assume all algae are alike.  Whether the
>question has to do with nitrogen nutrition or whatever (especially outside the
>chloroplasts), look for information on the organism of interest and its near
>relatives first.

>In general, plants/algae have enzymes available for use of ammonium.  In
>fact, nitrate is converted to ammonium before it can be used for amino acid
>synthesis.  However, ammonium (esp. converted to ammonia) is also toxic. 
>Therefore, in the presence of ammonium (which CAN cross membranes in
>ammonia form without a specific transporter), your alga must have the
>ability to detoxify (use quickly, sequester, keep intracellular concentration
>low) the ammonium before it succumbs.

>Kathy Schmid
>schmid at butleru.edu

Hear hear!  Good answer.  It is a rash statement to say that "algae
are plants" without defining what you mean by plants, and rasher still
to assume that all algae are similar metabolically.  In fact there is
good reason to believe that algae display far more metabolic diversity
than do plants, and to generalize is extremely difficult.

For some detailed information about the growth requirements of a
variety of algae, consult the UTEX algal culture collection catalog
which is published as a supplement to the Journal of Phycology: Starr,
R. C. and Zeikus, J. A. 1993.  UTEX -- The Culture Collection of Algae
at the University of Texas at Austin.  J. Phycol.  supplement to v. 29

Charles F. Delwiche       < no quote.  I'm uninspired today. >
Dept. Biology, I.U.       
Bloomington, IN 47405     
--> delwiche at bio.indiana.edu is my preferred email address

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