Question:Purple flower peas

PROFDHW at aol.com PROFDHW at aol.com
Sun Dec 17 16:47:05 EST 2000


If you read Mendel's paper you will make some amazing discoveries. He never 
did use purple flowers as one of his traits. You can read a popular English 
translation of Mendel's paper at MendelWeb:

http://www.netspace.org/MendelWeb/Mendel.plain.html


Here is a clip from that translation. Find the "purple flower" trait if you 
can.

<<<<<<<<<<
The characters which were selected for experiment relate: 

1.  To the difference in the form of the ripe seeds. These are either round 
or roundish, the depressions, if any, occur on the surface, being always only 
shallow; or they are irregularly angular and deeply wrinkled (P. quadratum).
2.  To the difference in the color of the seed albumen (endosperm). The 
albumen of the ripe seeds is either pale yellow, bright yellow and orange 
colored, or it possesses a more or less intense green tint. This difference 
of color is easily seen in the seeds as their coats are transparent.
3.  To the difference in the color of the seed-coat. This is either white, 
with which character white flowers are constantly correlated; or it is gray, 
gray-brown, leather-brown, with or without violet spotting, in which case the 
color of the standards is violet, that of the wings purple, and the stem in 
the axils of the leaves is of a reddish tint. The gray seed-coats become dark 
brown in boiling water.
4.  To the difference in the form of the ripe pods. These are either simply 
inflated, not contracted in places; or they are deeply constricted between 
the seeds and more or less wrinkled (P. saccharatum).
5.  To the difference in the color of the unripe pods. They are either light 
to dark green, or vividly yellow, in which coloring the stalks, leaf-veins, 
and calyx participate.*
6.  To the difference in the position of the flowers. They are either axial, 
that is, distributed along the main stem; or they are terminal, that is, 
bunched at the top of the stem and arranged almost in a false umbel; in this 
case the upper part of the stem is more or less widened in section (P. 
umbellatum).
7.  To the difference in the length of the stem. The length of the stem is 
very various in some forms; it is, however, a constant character for each, in 
so far that healthy plants, grown in the same soil, are only subject to 
unimportant variations in this character. In experiments with this character, 
in order to be able to discriminate with certainty, the long axis of 6 to 7 
ft. was always crossed with the short one of 3/4 ft. to 1 and 1/2 ft.
>>>>>>>>>>>

The trait that has been converted to "purple flowers" by the text book 
authors (presumably because students are too dumb to understand the truth) is 
#3, the color of the seed coat. Notice that this also suggests a good example 
of pleiotropy from the pen of Mendel himself (who clearly understood it)!

I always introduce Mendel with the stem length character because it offers 
the opportunity to show that what Mendel was talking about was not a plant 
height element but one that regulated the ability of the plant to grow to a 
variable "normal"  (as in typical) height or to be "dwarf" with a variable 
height no greater than 1 and 1/2 ft. Another great aid for student success in 
this area is to use only A/a or B/b to designate the simple Mendelian traits. 
What do we gain with T/t for tall (actually normal in the sense of typical) 
vs. dwarf? How does Y/y clarify anything in a yellow vs. green cross? How 
does it make the problem easier to interpret? When written rapidly on a black 
or white board the upper and lower case Y's become impossible to distinguish. 
Mendel never used anything but A/a and B/b.

Good luck finding purple-flowered pea plants (if you still want them).

Dave Williams
Science Department
Valencia Community College, East Campus
701 N. Econlockhatchee Trail
Orlando, FL  32825
407-299-5000 x2443
profdhw at aol.com


In a message dated 16/12/00 11:25:43 PM, hesperaloe at aol.com writes:

>I am looking for purple flowered peas to show my class when I talk about
>Mendel's work.  All the peas I have planted from vegetable seed packs are
>white.
>
>I am thinking of buying ornamental sweet peas. Any other suggestions?
>
>                                    Peter


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