Hey JohnT:
I thought I would pass your question to Dr. Congo Joe. Here is his reply....
Question: If the stigma is clipped off before receiving pollen can the
ovary still be pollinated?
+++++++++++++
Not likely. The pollen is thought to need a special environment in
order for the pollen tube to germinate. Thus, removal of the stigma
surface prevents pollen from correctly growing.
After the pollen lands it grows a tube (the tube looks like a root but
is not a root). The tube grows down into the style and carries the
sperm nucleus to the ovary. The sperm nucleus must move down through
the pollen tube in order to be united with an ovule; only when the sperm
nucleus enters the ovary cell is it considered that pollination occurs.
So, pollination (in the sense of fertilization) actually requires that
the pollen have a correct environment for germination, then successful
pollen tube elongation must occur, and finally the sperm nucleus must be
delivered through the tube to unite with the ovary.
There can be many hours between when the pollen lands, and when the
sperm nucleus unites with the ovule. Removing the stigma would mean
that pollen would land on a cut surface, and it is thought the proper
pollen tube germination does not happen in such a case.
Note from the troll..... I'm growing a cactus plant that Joe collected on
one of his field trips. Called a "horse crippler" wicked spines
Joe was a PhD of Botany at Auburn, plant pathogens his specialty. He now works in
the private sector with the human genome.
More to follow. (I knew my friends would come through!!!)
|