Definition of Plant

Russell_Goddard rgoddard at valdosta.edu
Fri Oct 8 07:33:29 EST 1999



On Thu, 7 Oct 1999, David Hershey wrote:

> the Plant Kingdom
> consists of just bryophytes and vascular plants, so I was surprised that

> the American Society of Plant Physiologists'.. states...
> that "Plants exhibit diversity in size and shape ranging from single
> cells to gigantic trees." 
> 
> Is there still disagreement over what organisms are included in the
> Plant Kingdom?
> 

My answer?  I don't think there is that much disagreement with what
organisms are included in the Plant Kingdom, but there is disagreement on
what organisms might be included under the TERM, "plant."  I tell my
students that the word plant is a term and not a taxonomic classification.
This makes it much easier for them to digest the evololutionary origins of
terrestrial plants.  As a term, many definitions of the word "plant" are
in use by biologists (and others).  You really have two questions above.
"What organisms should be included in Kingdom Plantae?"  ...and "what is a
plant?"  The word "plant" is not necessarily synonymous with organisms in
Kingdom Plantae.  I spend my first lecture/discussion in botany class on
this topic, "What is a plant."  There is no clear answer.  I use a broad
definition that includes all photosynthetic (chlorophyll a containing)
organisms in three Kingdoms.  I then spend time talking about the
cyanobacteria in general and prochlorophytes specifically for making
connections to the eukaryotic algae.  I like to show the diversity of
form and function in several Phyla of algae and their similarities to
terrestrial plants, then spend more time on the Chlorophyta as containing
possible progenitors to what we now include in Kingdom Plantae.  So for
me, they are all "plants" but obviously this is debatable.  As botanists,
do we need to define this term more specifically among ourselves?

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