Definition of Plant
KSchmid at MAIL.BUTLER.EDU
Fri Oct 8 17:25:22 EST 1999
My understanding is that what matters in distinguishing members of the plant
kingdom (embryophytes) from the macrophytic algae is not that they have
but that the embryos are protected, a very useful characteristic for
on dry land. Specifically, fertilization takes place inside an archegonium
and/or ovule, and the zygote develops into an embryo right there, within the
protection of the archegonium/ovule. The green algae thought to be closest
the plant kingdom (e.g. Chara, Coleochaete)have internal fertilization, but
zygote does meiosis right away -- no 2n embryo to be protected. Other algae
with lovely 2n embryos (e.g. Fucus)produce them from zygotes formed by
fertilization, so there's no automatic protection.
On the kingdom question.... Although grouping embryophytes and charophytes
together seems straightforward, I think there's some evidence that the green
as a whole are polyphyletic. Of course, their chloroplasts may be more
related than their nuclei.
Dr. Katherine M. Schmid
Dept. of Biological Sciences
4600 Sunset Ave.
Indianapolis IN 46208
kschmid at butler.edu
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