At 2:28 PM -0500 9/2/99, Jon Greenberg wrote:
>I have been criticized for referring to pollen as the male gamete. How
>do you all handle this issue? Do you say that seed plants have sperm
>cells, and the pollen is simply a structure that carries these gametes?
>>Many thanks.
>>Jon Greenberg
Hi Jon,
The pollen grain is an endosporic microgametophyte.
The pollen wall (that causes allergic reactions in some) is
the old microspore wall. The microspore cytoplasm inside
this wall has divided to make two cells: the tube cell and
the generative cell. The generative cell divides to make
two sperm cells. In some species this division occurs before
the pollen is shed; in others the sperm are not produced
until the pollen tube has grown into the tissues of the
carpel.
So thinking of the pollen grain as a carrier of two sperm
is OK for some species...for others it would be wrong.
But for me, at least, relegating the pollen grain to
just a transport container would be leaving out some
really interesting biology! The growth of the pollen
tube, stylar compatibility, digestive process, chemotaxis,
sperm release, sperm sorting, and other such topics are
what make pollen biology fascinating.
This microgametophyte has been reduced to only a few
cells, yet this multicellular haploid phase of the
life history of plants is amazingly intricate!
ross
________________________________________________________________
Ross Koning | koning at ecsu.ctstateu.edu
Biology Department | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA | fax: 860-465-4479
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