Male Gametophyte Female Gametophyte. Ovary and 5 stigma lobes of Sagina nodosa (Knotted Pearlwort,...
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Transcript of Male Gametophyte Female Gametophyte. Ovary and 5 stigma lobes of Sagina nodosa (Knotted Pearlwort,...
Ovary and 5 stigma lobes of Sagina nodosa (Knotted Pearlwort, Caryophyllaceae). Note stigmatic papillae.
http://remf.dartmouth.edu/images/botanicalPollenSEM/source/12.html
Malvaceae Sildalcea malviflora
Onagraceae Oenothera fruticosa
Liliaceae Lilium auratum
Convovlulaceae Ipomea purpurea
Euphorbiaceae Ricinus communis
Asteraceae Helianthus annuus
Both parental genes expressed by pollen and by stigma
S1 dominant over S2 in pollen but codoiminant in stigma ; S2 and S3 are co- dominant in both
Only S1 (when present) is dominant in pollen and stigma
Sporophytic Incompatibility
If expressed genes match, pollen grain won’t germinate.
Pollen Tube
Stigmatic papillae
Pollen Grain -polyporate (with many round pores)
Sagina nodosa (Caryophyllaceae)
Lonicera canadensis (Caprifoliaceae), Fly-bush honeysuckle, stigma and portion of style. Note numerous germinated pollen grains and the few pollen tubes that are ahead of all the others.
Fertilization
Syngamy
Zygote
Triploid Endosperm nucleus
Note the egg and central cellHave incomplete cell walls. The sperm have no cell walls.
Torenia fournieri, wishbone flower (note arched stamens) (Scrophulariaceae)
Note the embryo sac (female gametophyte) extends out of the micropylar opening. FA=filiform apparatus.
Higashiyama, T. et al. 2001. Pollen Tube Attraction by the Synergid Cell. Science 293:1480-1483.
Torenia pollen tube growth.
Ovule with embryo sac
Arrowheads ( ) =micropylar end of embryo sac.
Arrows ( )= pollen tubes
Pollen tubes bypass the embryo sac with 2 ablated synergids (2 triangles)even though the egg and central cell are functional.
Note the pollen tube (arrow) is attracted to the embryo sac with both synergids even though the egg and central cell have been ablated,
This fertilized egg cell could not attract any more pollen tubes even though there was still one functional synergid. Thus fertilization shuts down any remaining signaling from the intact synergid.
Four-celled/four-nucleate Nuphar (Nymphaeaceae) female gametophyte.
2 Synergids (sy)
1 Egg (e) located behind the synergids (but shown in the inset)
1 nucleus (cc) in the central cell (defined by the dark region below the egg and synergids)
Scale bar, 10 µm.
2nd Fertilization in Nuphar (fusion of the sperm and central cell nuclei)
a. Sperm nucleus approaches
b&c. Sperm engulfed by central cell nucleus
d. The now diploid endosperm begins mitotic division (prophase).
Scale bar, 10 µm.
The typical 7-celled, 8-nucleated embryo sac is shown in a.
The question is did the Nymphaeaceae and other “basal” angiosperm families loose the antipodal cells and one of the central cell nuclei?
Or did the other groups gain the antipodals and extra central cell nucleus?