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Female Gametophyte. Male Gametophyte. Ovary and 5 stigma lobes of Sagina nodosa (Knotted Pearlwort, Caryophyllaceae). Note stigmatic papillae. Onagraceae Oenothera fruticosa. Malvaceae Sildalcea malviflora. Liliaceae Lilium auratum. Euphorbiaceae Ricinus communis.

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Presentation Transcript
slide1

Female Gametophyte

Male Gametophyte

slide2

Ovary and 5 stigma lobes of Sagina nodosa (Knotted Pearlwort, Caryophyllaceae). Note stigmatic papillae.

slide3

Onagraceae Oenothera fruticosa

Malvaceae Sildalcea malviflora

Liliaceae Lilium auratum

Euphorbiaceae Ricinus communis

Convovlulaceae Ipomea purpurea

Asteraceae Helianthus annuus

http://remf.dartmouth.edu/images/botanicalPollenSEM/source/12.html

slide4

Stigma of Arabidopsis

http://mips.gsf.de/proj/thal/ens/stigma.html

slide7

Sporophytic Incompatibility

If expressed genes match, pollen grain won’t germinate.

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

slide8

Sagina nodosa (Caryophyllaceae)

Pollen Tube

Stigmatic papillae

Pollen Grain -polyporate (with many round pores)

slide10

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.

slide12

Fertilization

Triploid Endosperm nucleus

Zygote

Syngamy

Note the egg and central cell

Have incomplete cell walls.

The sperm have no cell walls.

slide14

Higashiyama, T. et al. 2001. Pollen Tube Attraction by the Synergid Cell. Science 293:1480-1483.

Torenia fournieri, wishbone flower (note arched stamens) (Scrophulariaceae)

Note the embryo sac (female gametophyte) extends out of the micropylar opening. FA=filiform apparatus.

slide15

Torenia pollen tube growth.

Ovule with embryo sac

Arrowheads ( ) =micropylar end of embryo sac.

Arrows ( )= pollen tubes

slide16

Torenia experiment

Excised Style Pollen Tubes Ovules

slide18

Note the pollen tube (arrow) is attracted to the embryo sac with both synergids even though the egg and central cell have been ablated,

Pollen tubes bypass the embryo sac with 2 ablated synergids (2 triangles)even though the egg and central cell are functional.

slide19

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.

slide20

Williams & Friedman’s (2002) article on the diploid endosperm made the cover of Nature.

slide21

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.

slide22

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.

slide23

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?

slide24

4-celled plesiomorphic

Which is ancestral?

• Either triploid endosperm evolved twice from a diploid condition during the early evolution of angiosperms (a)

•Or diploid endosperm evolved twice from a triploid condition (b).

7-celled plesiomorphic