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gymnosperm sex

Young, Helen hjyoung at middlebury.edu
Tue Nov 12 10:22:49 EST 2002

We are looking at gymnosperm reproduction this week in lab and I find that,
as always, I am baffled by how complicated it is.  In particular, there are
two points in fertilization and development where abortion occurs and I'm
wondering if anyone knows the evolutionary significance of this.  
	One is at the early zygote development stage, where more than one
archegonia per megagametophyte may be fertilized and begin development, but
usually only one matures successfully.  These zygotes are genetically
different, as they result from different egg and sperm fusion.  Is there
competition among them that is mediated by genotype?
	The second is at the proembryo stage, where each zygote produces
many "proembryos", of which only one per zygote is successful.  These
proembryos are genetically identical so it doesn't really matter which one
"wins", but why do they produce more than one anyway?

Why is so much redundancy present in the gymnosperm sexual phase?

Helen Young
Helen Young
Biology Department
Middlebury College
Middlebury, VT 05753
hjyoung at middlebury.edu


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