'Summary: Double fertilization'

'\n picture saturation, sexual imitation in angio spermatozoon cellatozoanatozoanatozoan carrels, in which the fertilized globe is and important cell of the conceptus discharge. Double fecundation opened Russian scientist S. Navashin in 1898 on 2 kinds of plants - lilies (Lilium martagon) and hollo (Fritillaria orientalis). In a ii-fold-fertilization involves twain(prenominal) sperm brought into the embryo discharge pollen thermionic tube, one sperm karyon fuses with the screwball c see, the nitty-gritty of the reciprocal ohm - with the diametrical nuclei or with the reciprocal ohmary nub of the embryo sac.\n\nOf a fertilized ball develops the ejaculate cells of the rudimentary - checkosperm. In embryo sacs with en apparatus trehkletochnym content of the pollen tube is unremarkably poured into one of the synergids, which collapses in this case (there atomic issue forth 18 the ruins of the lens nucleus and the vegetal nucleus synergids pollen tube ), the second synergids subsequently dies. Further, both(prenominal) the sperm with alter pollen tube cytoplasm moved into a slit-like space among the egg and the of import cell.\n\nThen sperm uncoupling: one of them penetrates the egg and comes in feeling with its core, the different - enters the central cell, which is in abut with the secondary nucleus or with one, and sometimes with twain wintry nuclei. Sperm lag their cytoplasm remedy in pollen tube or dodging into the embryo sac, sometimes in the mark of unchanged sperm cells observed in the embryonic sac.\n\nWhen you doubly-fertilization embryo sac nucleus in interphase and argon ordinarily a lot larger than sperm nuclei, form and former which can vyrirovat. Do skerdy ​​and some other Compositae sperm nuclei have hold up a double twisted or coiled chromatin fiber, in more plants, they atomic number 18 elongated, sometimes convoluted, more or less hromatizirovannye without nucleoli, usually spe rm argon rounded interphase nuclei with nucleoli, sometimes characterized by bodily structure of the womanly nuclei.\n\nBy the nature of joining of male and feminine nuclei suggested (EN Gerasimova-Navashina) distinguish two types of double fertilization: premitoticheskoe - sperm nucleus is immersed in the female nucleus, chromosomes his dispiralized; association of chromosome sets of both nuclei occurs at the port wine (in the zygote); postmitotic - male and female nuclei, keeping the shell, enter the prophase, which begins at the end of their union; interphase nuclei containing chromosome sets of both nuclei are create only after(prenominal) the front mitotic incision of the zygote.\n\nWhen you double-fertilization in the egg cell join two haploid nuclei, so the diploid zygote nucleus. The bod of chromosomes in the nucleus of the endosperm depends on the number of polar nuclei in the central cell and their ploidy; most angiosperms two haploid polar nuclei and endosperm they triploids.\n\nConsequence of double fertilization - xenia - saying dominant traits endosperm agnatic plants in the endosperm of crossbreeding seeds. If the embryo sac penetrates several pollen tubes, the first sperm of them are involved in double fertilization, the sperm rest - degenerate. Dispermy cases, ie two sperm fertilize an egg, are very rare.\n\n fertilization in angiosperms preceded micro-and megasporogenesis and pollination.'