geeta at life.cc.sunysb.edu
Sat Nov 22 12:25:38 EST 1997
Janice M. Glime (jmglime at MTU.EDU) wrote:
: While we're on the subject of the embryo sac, does anyone know for sure
: if the polar nuclei of Lilium unite before the sperm arrives? I re-read
: Bold, Alexopoulos, and Delevoryas, but it was not stated. The
: illustration of Lilium shows separate nuclei, but in discussing the
: general case the authors state that these (polar nuclei) may unite before
: or at fertilization to form the secondary nucleus.
According to Maheshwari (1950), the mature embryo sac in Fritillaria and
Lilium consists of "three haploid cells (the egg and two synergids), three
triploid cells (the antipodals), and a tetraploid secondary nucleus formed
by the fusion of the two polar nuclei, one haploid and the other triploid"
Johri et al (Comparative Embryology of Angiosperms) say this:
"Double fertilization of the post-mitotic type occurs in the Fritillaria
type of embryosac of Tulipa spp. But as the lower polar nucleus
(triploid) does not take part in the formation of the
secondary nucleus, the primary endosperm nucleus is diploid."
This time I didnt try to pull anything out of my (failing) memory bank.
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