Tri- & tetra-cotyledons in dicots

[Randall Tyers]

In article <9302100732.AA02782 at net.bio.net> UGG00005 at VM.UOGUELPH.CA (Nanfei Xu)
writes:
>[...]
>     I'm studying alfalfa embryogenesis.  Alfalfa (Medicago sativa L.) is a
>dicotyledonous plant.  However, there are quite a few tri- or tetra-
>cotyledonous embryos from the plants I grow in growth chamber.  The ratio of
>di-/(tri- + tetra-) is roughly 3:1 for all the plants with different amount of
>fertilizer.  Does anybody out there know why there is tri- or tetra-cots on
>dicots plant?  What is the evolutionary relationship of tri- or tetra-cots to
>mono- and dicots if there is any?  

Your "Tri-/Tetra-cots" are still the same species of plant (alfalfa)which is a
member of the Order Dicotyledones.  Thus, I'm not sure that I understand
this question.

> In general, is tri- or tetra-cots derived
>from the fusing of two early stage embryos, or is it from one zygote? 

I know that many Gymnosperms have *many* cotyledons and this has nothing
to do with fusion so I would suspect that they come from one zygote.

> Is there
>any description of developmental morphology?  Is this character inheritable?
>Any discussion on the net or information to me is greatly appreciated.

A very useful persn for you to contact would be Dr. Kaplan.  He can be
reached at 510 642-4187 or 111 Koshland Hall, UC Berkeley, Berkeley CA
94720

>...
>Nanfei Xu                                 Phone: 519-824-4120 Ext. 8347
>Department of Botany
>University of Guelph                      E-mail: UGG00005 at VM.UOGUELPH.CA
>Guelph, Ontario, Canada                                    or
>N1G 2W1                                           BOTXU at VM.UOGUELPH.CA
 
Randall Tyers     tyersome at insect.berkeley.edu