(none)

Geeta Bharathan geeta at life.cc.sunysb.edu
Fri Nov 21 17:39:35 EST 1997


Dr. Magaly Rincon (frinconm at NEXUS.MWSU.EDU) wrote:

: In tetrasporic embryos (e.g., Lilium), the polar nuclei is tetraploid.
: During fertilization one sperm fuses with the polar nuclei and one with the
: egg.  This means then that the endosperm is pentaploid.  Is this
: interpretation correct?

Embryo-sacs (ie the female gametophyte) are tetrasporic. This means that
no cells walls form after either Meiosis I or II. This results in a single
megaspore that contains four haploid nuclei. In Lilium each of these
nuclei divides once mitotically, to form an 8-nucleate gametophyte
(=embryo-sac).

The two polar nuclei are each haploid, so after fusion with one haploid
sperm nucleus from the pollen, the endosperm nucleus that forms is
triploid.


--Geeta Bharathan



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