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SUPERFLUOUS. “Gymnosperms lacking double fertilization dominate large areas of the Earth, e.g. the Taiga or Northern Coniferous Forest. Therefore, double fertilization is not a requirement for success in seed plants.” https://lnkd.in/dJZ98Vs View in LinkedIn

THE WHY. “We are not positive why double fertilization occurs. Arthur Cronquist (1971) considered double fertilization a "mere evolutionary happenstance." One possible advantage of double fertilization is that the plant does not invest energy in seed nutritive tissue until after an egg has been fertilized. Another possible advantage is that the endosperm nucleus is very active and divides rapidly. It forms the nutritive tissue very quickly. Rapid seed development has obvious advantages.’ https://lnkd.in/dJZ98Vs View in LinkedIn

WHY DOUBLE FERTILIZATION OCCURS. “Of the two sperm cells, one sperm fertilizes the egg cell, forming a diploid zygote; the other sperm fuses with the two polar nuclei, forming a triploid cell that develops into the endosperm. Together, these two fertilization events in angiosperms are known as double fertilization. After fertilization is complete, no other sperm can enter. The fertilized ovule forms the seed, whereas the tissues of the ovary become the fruit, usually enveloping the seed.” https://lnkd.in/dQYs2c2 View in LinkedIn

OPEN ISSUES. “Determination of fertilization targets during the gametic phase of double fertilization is still largely unknown but must require complex gamete recognition and/or blocking polyspermy in both female gametes.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn

NUANCES. “The transcriptional activation of male and female genomes in the zygote is critical for establishing apical–basal cell polarity over a long period of time before the first division. Our data suggest that unlike egg cell functioning in animals such as hamster, in Arabidopsis, a single spike of [Ca2+]cyt at fertilization with a duration that is much shorter than that observed during maize in vitro fertilization, might be sufficient for blocking polyspermy and initiation of the developmental programme.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn

CELL CYCLE SYNCHRONY. “Flowering plants show unique cell cycle control in fertilization among eukaryotes; sperm cells of Arabidopsis in G2 phase have been proposed to fuse with the egg cell in G1/S or G2 phase and with the central cell in G2 phase. Different mechanisms of cell cycle arrest and activation might exist.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn

SIGNATURE SIGNALS. “Following pollen tube discharge and plasmogamy, the egg and central cells displayed transient Ca2+ spikes, but not oscillations. Only the events in the egg cell correlated with the plasmogamy. In contrast, the synergid cells displayed Ca2+ oscillations on pollen tube arrival. The two synergid cells showed distinct Ca2+ dynamics depending on their respective roles in tube reception. These Ca2+ dynamics in the female gametophyte seem to represent highly specific signatures that coordinate successful double fertilization in the flowering plants.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn

PULSES OF SIGNAL. “We observed Ca2+ dynamics in all the female gametophytic cells directly involved in the double fertilization of Arabidopsis. The egg cell displayed two distinct spikes on pollen tube discharge and gamete fusion, respectively.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn

SINGLE WINNERS. “In the flowering plants, the mechanism of polyspermy block is unknown. However, the phenomenon was recognized by in vitro fertilization analysis in maize about 20 years ago.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn

ELECTRICAL SIGNALS. “In animals like frogs and several marine invertebrates, polyspermy (the fertilization of an egg by two or more sperm cells) is prevented by an electrical charge across the surface of the egg (fast block in a few seconds) and/or by modification of the extracellular egg coat by a secretion reaction (slow block in dozens of seconds), following gamete fusion. A Ca2+ wave in the fertilized egg triggers the secretion reaction associated with the slow polyspermy block.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn