| 单词 | polar nucleus |
| 释义 | > as lemmaspolar nucleus polar nucleus n. Botany (in angiosperm reproduction) either of the two haploid nuclei which move from the poles of the embryo sac to the centre and fuse with the male gamete to form the triploid primary endosperm nucleus. ΚΠ 1882 S. H. Vines in tr. F. G. J. von Sachs Text-bk. Bot. (ed. 2) 581 In some instances the two polar nuclei meet, not in the centre, but towards the upper end of the embryo-sac. 1945 Q. Rev. Biol. 20 246/1 It was at first supposed that suppression of meiosis, or parthenogamy from a polar nucleus, might cause their appearance. 1992 M. Ingrouille Diversity & Evol. Land Plants 122 A double fertilization occurs with the formation of a diploid zygote (sperm nucleus plus egg) and a triploid endosperm nucleus (male gamete plus two polar nuclei). < as lemmas |
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