HYB: ploidy and extra petals
From: Bill Shear <BILLS@hsc.edu>
Ploidy refers to sets of chromosomes and has nothing to do with the numbers
of sets of flower parts. I think Dan and Marilyn were just joking.
Multiplication of flower parts most often results from some slight damage
to the flower primordium at a very early stage of development, or from an
anomalous cell division early on. It occurs in most cases strictly at
random, though does crop up here and there as a stable, genetically
determined trait ("double" flowers in many groups). I suspect the plant
developmental biologists have worked all this out in great detail.
"Doubleness" in Japanese irises is something else. Here, a set of falls
substitutes for standards, and in more extreme forms, the anthers and style
arms become petal-like as well and multiply in number (the peony form).
This is clearly a stable genetic trait; one might suggest that becoming a
fall petal is the "default option" and if the gene that turns the
primordium into a standard, anther or style arm is defective, they all just
follow the program and become fall petals.
Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<bills@hsc.edu>
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