micropyle (adj. micropylar) A canal in the coverings of the nucellus through which the pollen tube usually passes during fertilization. Later, when the seed matures and starts to germinate, the micropyle serves as a minute pore through which water enters.

micropyle
1. A small opening in the surface of a plant ovule through which the pollen tube passes prior to fertilization. It results from the incomplete covering of the nucellus by the integuments. It remains as an opening in the testa of most seeds through which water is absorbed.

2. A small pore in some animal cells or tissues; for example, in insect eggs (see chorion).

micropyle (adj. micropylar) A pore in the egg membrane of an insect oocyte, which allows sperm to enter and fertilize the egg.