the pollen tube ussualyy enters the embrio sac

1. through one of the synergids
2. by directly penetating egg
3. between one synergid and central cell
4. by knocking off the antipodal cells

The pollen tube ultimately enters an ovule through the micropyle and penetrates one of the sterile cells on either side of the egg (synergids). Thesesynergids begin to degenerate immediately after pollination. Pollen tubes can reach great lengths, as in corn, where the corn silk consists of the styles for the corn ear and each silk thread contains many pollen tubes.