From: ted.held at us.henkel.com (ted.held at us.henkel.com) on 2008.01.07 at 18:01:38(16930)
Dear List,
I have managed to finish the latest Aroideana. It's probably a good thing
for me this comes out only once a year as it seems like it takes me a year
to read and digest what's in one. Being a lay person, some of the articles
can be heavy-going. The one entitled "The Chromosome Numbers of the Aroid
Genera", by Dr. Bogner, is a case in point. I am trying to sort out what
the apparent promiscuity of aroids with regard to chromosome numbers might
mean. Here are some questions?
1. Do all the plants within a given species have the same basic "X" number
of chromosomes? Does this mean a species within the genus Landoltia, for
example, might have a normal 2n chromosome count of 40 with haploid (2n =
20), diploid (2n = 80), etc., variations, but not 2n = 46? So if you have
two plants, one with 2n = 40 and another with 2n = 46, do you know you
have two different species?
2. Can plants with different chromosome counts be cross fertile? Can a 2n
= 40 plant produce viable seed with its own diploid? How about with a
plant in the same genus with a chromosome count of 2n = 46?
3. What happens when a plant messes up and undergoes aneuploidy.
Aneuploidy is defined in the text as when some type of evolution takes
place where the offspring end up with a few extra chromosomes here and
there. Doesn't this mess up the plant? If not, why not?
4. Similarly, there is a term called dysploidy where a few chromosomes
don't make it into the new plants, or where old chromosomes get pieces
chewed off, somehow. Don't plants need at least a portion of the
information contained in the chromosome arms? Doesn't this mess up the
plant? If not, why not?
5. Can a plant that has experienced aneuploidy or dysploidy produce viable
seed with a normal-count plant? Or does the plant have to reproduce
vegetatively for a while until there is another receptive brother or
sister with whom to mate?
6. How much messing around with chromosome numbers does it take before the
morphological differences are large enough to produce a new genus?
Please take pity on me. When I went to school all this was very new. Come
to think of it Darwin was new stuff back in those days.
Ted.
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