Stigma-Ovary distances explained (sort of)

MALOUF@ESTD.NRL.NAVY.MIL
Tue, 23 Nov 1993 15:31:06 -0500 (EST)

Clark Brunt writes:

>I don't know what the logic of this stamen/stigma distance business is.

I only recently had this 'business' explained to me. My understanding
is as follows, and comments from more knowledgeable individuals are
certainly welcome.

After pollen is placed on the stigma and is worked into the orifice
leading to the ovary, it grows a tube down the style toward the
ovary and then injects its genetic material through the tube
into the ovary. The length of the tube grown from the pollen
will correspond to the distance between stigma and ovary for
a given species.

Now, if you're trying to form hybrids from two plants whose
flowers have very different stigma-to-ovary distances, you
need to be prudent as to which pollen is placed on what flower.
For example, if you use pollen from the plant with the short
stigma-to-ovary distance on a flower with a longer corresponding
distance, then the pollen will not grow a tube long enough
to reach the ovary of the latter flower. Fertilization will
be difficult/improbable. If you work it the other way around,
the pollen will certainly grow a tube long enough to span
the (shorter) distance and fertilization is more likely. I
understand that,in some of these cases, the tube grows too
long and becomes kinked so that fertilization does not occur.
Nevertheless, fertilization seems more probable than in the
former example.

Rob Sacilotto has used this philosophy successfully to
form hybrids between Sarraceniae whose flowers were of
very different sizes. Sorry, I've forgotten precisely
which Saraceniae were used.

I want to thank those who responded to my original question,
especially those who brought to my attention that D. Binata
doesn't seem to self pollinate. That makes my experiment
a lot easier!

By the way, Clark, welcome back. I saw your posting on
rec.gardens, and at least one other person besides me
responded as well.