Re: Hybridizing/plant biology
- To: Multiple recipients of list <i*@rt66.com>
- Subject: Re: Hybridizing/plant biology
- From: B* S* <B*@hsc.edu>
- Date: Tue, 21 Oct 1997 08:01:51 -0600 (MDT)
Experience shows that only one style arm or stigmatic lip need be
pollinated to get a full pod.
However, one pollen grain can only fertilize one ovule. Thus if only a
very small amount of pollen were applied, not all the ovules would be
fertilized. Pollen grains are so small that so long as a visible amount is
applied to the stigmatic lip, there should be enough to pollinate all the
ovules.
There are caveats. In wide crosses, it is wise to use as much pollen as
possible and pollinate all three lips, since various kinds of
incompatibilities will render most of the pollen ineffectual. The more
pollen, the greater the chance of getting a seed.
Curiously, pollen grains are actually whole individual plants--the males of
the gameteophyte generation. Each grain contains only a few cells. Some
of these cells produce the pollen tube. When the pollen grain reaches a
compatible stigma, it germinates and a long tube quickly grows down through
the stigmatic tissues to reach the ovules (the unfertilized seeds within
the ovary). Two sperm nuclei then travel down this tube. One fertilizes
the egg in the ovule, and produces the embryo plant, and the other
fertilizes the endosperm, or stored food tissue, within the seed (this is
actually a triple fusion, so the endosperm is 3N).
Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<bills@tiger.hsc.edu>
