What causes pollen tubes to grow in the correct direction?

When a pollen grain lands on the stigma of a flower of the correct species , a pollen tube begins to grow. It grows through the style until it reaches an ovule inside the ovary. The nucleus of the pollen then passes along the pollen tube and fuses (joins) with the nucleus of the ovule.

How is the pollen tube guided toward the ovule?

The pollen tube ultimately enters an ovule through the micropyle and penetrates one of the sterile cells on either side of the egg (synergids). These synergids begin to degenerate immediately after pollination. … The pollen tubes that grow the fastest reach the ovules first and effect fertilization.

How is pollen germination controlled?

The production and maintenance of internal turgor in pollen and the pollen tube provide the driving force for pollen germination and tube growth. However, it is unknown how turgor formation is controlled when pollen absorbs water (hydration). During pollen germination, turgor is produced by the formation of vacuoles.

Why does the pollen tube grow towards the micropyle?

THE ROLE OF Ca+2 IN POLLEN TUBE GROWTH

If the pollen and the stigma are compatible, the pollen tube grows down the style of the carpel towards the micropyle. The tube nucleus and the sperm cells are kept at the growing tip by bands of callose. Calcium has long been known to play an essential role in pollen tube growth.