How do flowering plants form seeds after fertilization?

In flowering plants, the formation of seeds is a complex process initiated by pollination and completed through a unique mechanism known as double fertilization.12

The Process of Double Fertilization

When a pollen grain lands on the stigma of a flower, it germinates and grows a pollen tube down toward the ovule. This tube delivers two nonmotile sperm cells to the embryo sac.12

• Embryo Formation: One sperm cell fuses with the egg cell to create a diploid zygote, which subsequently undergoes cell divisions to develop into the embryo.12
• Endosperm Development: The second sperm cell fuses with two polar nuclei to form a triploid nucleus. This nucleus divides to create the endosperm, a nutrient-rich tissue that provides food for the developing embryo.132

Seed Maturation

Following these fertilization events, the ovule matures into a seed. The protective integuments of the ovule harden to form the seed coat, or testa. While the endosperm typically serves as the primary food storage, some plants store nutrients in the cotyledons or in a tissue derived from the nucellus called the perisperm. In many species, the surrounding ovary develops into a fruit to protect and aid in the dispersal of the seeds.241