acid phosphatase, was detected in the pollination drop of Welwitschia, it is not known whether it was secreted into the drop by nucellar
tissue, or it arrived in the drop after degenerative formation of the pollen chamber.
Although there were accessions with similar names (for example, Nucellar
Satsuma and Satsuma Owari), they do not appear to be related to each other.
After growing through nucellar
tissue for three days, from one to several pollen tubes approach the micropylar end of the female gametophyte [ILLUSTRATION FOR FIGURE 4A OMITTED].
The embryo was prominent and the nucellar
tissue was no longer present in control kernels indicating normal progression toward completion of the endosperm cell division stage.
In addition to the sexual or zygotic embryo, most citrus seeds also present nucellar
embryos, formed by somatic nucellus cells, characterizing the nucellar
polyembryony (FROST; SOOST, 1968).
The taxonomy and phylogeny of Citrus are complicated due to the high rate of bud mutation and the sexual compatibility between Citrus and related genera and the asexual reproduction through nucellar
embryony, which is characteristic in several Citrus species and most rootstock (Frost, 1943; Cameron, 1979).
developing MTOC is associated with the membranes of the nucellar
asexual reproduction by seeds) is a common trait in the genus, being apospory (in which a non reduced megagametophyte originates from a somatic cell, usually a nucellar
cell) the most frequent type, and diplospory (in which a non reduced megaspore originates from the reproductive cell itself, with the later failing to successfully complete meiosis) only of occasional occurrence (Quarin, 1992).
Relationships of seed size and shape with polyembryony and the zygotic or nucellar
origin of Citrus spp.
Citrus isozymes: Genetics and distinguishing nucellar
from zygotic seedlings.
in a cross-section of the nucellar
zone of one seed, a pollen tube was
callus of `Femminello' lemon selected for tolerance to Phoma tracheiphila toxin, shows enhanced release of chitinase and glucanase into the culture medium.