When a pollen grain germinates, a pollen tube pushes its way out through an aperture in the pollen grain wall,and the nuclei migrate into the tube.

 
  • 生殖细胞核分裂,形成两个仅由细胞核和细胞质构成的精子,其中一个将与卵受精,另一个则与极核融合形成胚乳核。
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