Ferns, fertilization

John H. Miller jhmiller at mailbox.syr.edu
Mon Feb 23 19:38:23 EST 1998


On Sun, 22 Feb 1998 21:54:42 -0800, mystic <mystic at lcc.net> wrote:

>Richard Blucher wrote:
>> 
>> Following up on a previous question/answer about ferns, I would
>> 
>> appreciate if someone could give me some help with two additional
>> 
>> question on the same subject:
>> 
>> 1) Since the male and the female gametes of the fern develop on the
>> 
>> underside of the gametophyte, is it a necessary condition for the
>> 
>> successful travel of the male gamete that there is water to fill the
>> 
>> void between it and the ground, or at least that the water is high
>> 
>> enough at the female gamete to allow it to make contact?
>
>Generally, the cohesive nature of water makes it unnecessary for there
>to be a 'sea' of water beneath the gametophyte.  It doesn't have a stem,
>per se, anyway, so there's not much room between it and the ground.  The
>sperm swim through the water adhering via surface tension to the
>gametophyte.
>> 
>> 2) If the male gamete is in fact 'dumped' into the 'sea' beneath it, is
>> 
>> its approach to the female gamete a random swim or is it attracted
>> 
>> specifically to the female gamete?
>
>I sometimes wonder if the male gametes aren't following a chemo-trail --
>but haven't seen any research on that subject.  Might make a pretty
>experiment.  Gametophytes are easy to grow on agar, under basic plant
>lights.  Keep 'em misted, but not too much.  It's really cool if you
>collect your spores from the wild.  Got mine from native epiphytic ferns
>in the East Tx. hardwood forest, and I got, besides gametophytes, lots
>of interesting algae, fungi, and tardigrades (water bears, invertebrate
>'algae grazers' that develop from dormant, spore-like structures.
>
>Hope this helps
>V. Appleman
>> 
>> Thanks
>> 
>>           Richard Blucher
>> 
>>
   Fern spermatozoids have been used since at least the late 19th
century to study chemotaxis--directed movement along a chemical
gradient.  A strong response is observed to gradients of malate ion,
and it is supposed that the archegonium produes malate which attracts
the sperm.  Work on this was done in the 50's by C.J.Brokaw.  If you
can get hold of The Botanical Review vol 34 (4): 1968 p 361 you will
find references to papers on sperm chemotaxis.

Regards,

John Miller



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