David,
Your list adds some important dimensions to the ASPB list. I wonder,
however, if your
item 14 should be reworded:
14. Plants often clone themselves, both vegetatively and by
self-pollination followed by self-fertilization to produce seeds. For
example, the pea cultivars Gregor Mendel started with were basically
self-pollinating clones.
I think the word clone (at least in plant biology) most often refers
to organisms that result from asexual production, that are
genetically identical to one another and to the parent (singular
because there is only one parent). Thus, self-pollination does not
fit this definition of clone completely. The offspring are not the
product of asexual reproduction (sperm and egg are involved). Only
when self-pollination occurs in a completely homozygous parent does
it produce genetically identical offspring.
Perhaps my definition of clone is simply too narrow. I would be
interested in what others have to say.
When one looks at both lists, it is clear that "plant" is used in a
very broad sense, not restricted to the Kingdom Plantae. This can
lead to lots of confusion. Would it not be a good idea to restrict
the word plant for members of Kindgom Plantae and then refer to
others as plant-like, or autotrophic, or .....?
I also would add two additional "themes" for introductory plant
biology which already
might be included in the ASPB and Hershey lists in slightly different form:
1. Most plants are stationary. This contrasts with most animals and
has had tremendous impact on plant biology. Consider the impact in
terms of energy (making food versus gathering food), water
conservation (plants store water, need to conserve water, etc. in
ways that animals do not), reproduction (enlisting the aid of pollen
vectors, retention of asexual reproduction in case a mate is not
found, etc.), etc. [Note: This simple point could be understood
even by children in lower elementary grades and would make plant
biology more interesting for them. However, when students arrive in
my college classroom, even after several K-12 exposures to biology,
they seem to have never heard of this fact!!]
2. Plant evolution (in Kingdom Plantae), has gone from organisms of
aquatic habitats to organisms increasingly better adapted to land
habitats. Virtually the whole of plant evolution can be seen in the
way that adaptive mutations have lead to better and better adaptation
to land environments. Fertilization in mosses, ferns, et al. is by
releasing sperm into the environment and requiring them to swim to
the egg (requiring at least a microaquatic condition) whereas in
higher plants the sperm are continuously bathed in cytoplasm, never
exposed to the environment. Development of vascular tissue increases
the efficiency of transporting water from soil to shoot. Seed habit
1) protects the embryo from drying, 2) allows embryo survival under
very extreme environmental conditions (freezing temperatures, fire,
etc.), and 3) allows for dispersal of the offspring from away from
one another and away from the parent plant. The last point also
relates to the first principle... that plants are stationary and many
are perennial. Without dispersal mechanisms, excessive intraspecific
competition (sibs with sibs and sibs with parents) would lead to loss
of life and perhaps extinction.
I have heard many teachers/professors criticize any lessons dealing
with plant life cycles. If the assigned task is merely to memorize
and recite the stages of a life cycle, I can see why they are ready
to reject the lesson. However, when taught as illustrations of the
principles listed above, the study makes an important point and
becomes very interesting to most students.
Dave Kramer
>Two common themes in plant biology are correlation of structure with
>function (e.g. stomata and gas exchange) and symbiosis (e.g. most
>plants are a symbiosis between a plant and a mychorrizal fungus,
>symbiosis between nitrogen fixing bacteria in numerous plant species,
>endosymbiont theory for origin of chloroplasts and mitochondria,
>beneficial endophytic fungi in some plants, animals as pollinators and
>seed dispersers, ant plants, human cultivation and artificial selection
>of plants, etc.)
>>The American Society of Plant Biologists' twelve Principles of Plant
>Biology are excellent:
>http://aspb.org/education/foundation/principles.cfm>>I expanded their list in a Nov. 29, 2004 post to this group:
>http://www.bio.net/hypermail/plant-ed/2004-November/007753.html>>>David R. Hershey
>http://www.angelfire.com/ab6/hershey/bio.htm>>_______________________________________________
>Plant-ed mailing list
>Plant-ed at net.bio.net>http://www.bio.net/biomail/listinfo/plant-ed
--
*********************
David W. Kramer, Ph.D.
Asst. Prof. of Evolution, Ecology, and Organismal Biology
Ohio State University at Mansfield
1680 University Drive
Mansfield, OH 44906-1547
Phone: (419) 755-4344 FAX: (419) 755-4367
e-mail: kramer.8 at osu.eduhttp://www.mansfield.ohio-state.edu/~dkramer/
