> I have students use Marsilea in plant morphology every year and it works
> well, although the sperm can be a little tricky. At normal room
> temperature, sperm become active in 12-24 hours and are viable for about
> 1-3 hours. They are best seen in the gelatinous matrix around the papilla
> on the megaspore. They will appear as corkscrews, although there is a
> large "head" (cell body) that often gets lost on the way to the
> archegonium. There are good pictures in the text Morphology of Plants and
> Fungi, by Bold, et al. A funnel-shaped area forms in the matrix, leading
> to the papilla, and here the sperm can swim somewhat more freely, but
> still very slowly. Sperm can be seen at 100 power once you know them well,
> but 430 is really needed, and of course 1000 is best. However, at those
> powers, the thick megaspore often makes the slide too thick and the
> objective hits the coverslip, crushing the megaspore and spilling starch
> crystals all over. After that, the matrix is disrupted and it is
> difficult, if possible at all, to see the sperm.
> The size of one megaspore is about equivalent to the size of a
> microsporangium that has in it many (about 64?) microspores. Megaspores
> are easily seen with the naked eye.
> All the exciting things in development happen in the first week. I have
> never gotten the plants to mature.
> Someone should start the Marsilea in intervals before lab (15, 18, 21,
> 24 hours) are best for hitting the sperm in action. The needed time
> depends on the temperature and the stage of development of the spores. We
> used to receive sporocarps with mature megaspores, i.e., they already had
> papillae. Now they usually have flat ends and the papillae develop after
> we open the sporocarp.
> To prepare these, chip a bit off the sporocarp at the end opposite the
> peduncle. If only a tiny bit is removed, the gelatinous ring should
> emerge as a ring. It will begin to swell and should be mostly emerged and
> in a ring after one hour. We use tap water, but of course chlorine will
> affect viability. You might want to let it sit for a while. Distilled
> water does not work, I assume because it is so hypoosmotic.
> In 24 hours, the calyptra (papilla tissue) will begin to swell and the
> embryo shape will be evident. By 48 hours these will be well developed
> and roots and shoots will be evident. The gametophyte (calyptra) will
> develop rhizoids. Microspores can be seen mostly floating on the surface
> like pollen grains.
> I find it helpful to also have prepared slides of a c.s. of the
> sporocarp so students can see the relationships of positions within the
> sporocarp. That may be less important for your purposes.
> THis lab is best if each student can have a sporocarp and petri plate
> with water and lots of light, but there are enough megaspores for a whole
> table of students to share if need be. They need to be sure there is
> enough water that the spores won't dry out. We have students come daily
> the first few days to observe and make drawings. If that is not possible,
> I would advise having a series of ages (1 per day) available from
> previously started material. One-week worth is plenty for that.
>> Janice
> ***********************************
> Janice M. Glime, Professor
> Department of Biological Sciences
> Michigan Technological University
> Houghton, MI 49931-1295
>jmglime at mtu.edu> 906-487-2546
> FAX 906-487-3167
> ***********************************
>>> > Urchin disaster, and development looms in intr bio. I have some Marsilea
> > sporocarps and have been testing them out. We'd like the students to
> > follow development over a week or so. Anyone done this? I have the short
> > descriptions available from the ABLE procedings, but they do not describe
> > development much. Also, what is the best way to separate micro and
> > megasporangia? Just how big are the sperm and how long are they active?
> > What else should I know? The lab is next week so any immediate help would
> > be much appreciated!
> >
> > Susan Schenk
> > sschenk at jsd.claremont.edu> > fax: 909-621-8588
> > phone: 909-607-4018
> >
>
