Which structure is formed after the fusion of second male gamete with polar nuclei?

Primary endosperm nucleus

The structure formed after the fusion of the second male gamete with polar nuclei is the primary endosperm nucleus. This is a triploid (3n) cell that is formed by the fusion of two haploid (n) polar nuclei and one haploid (n) sperm nucleus. The primary endosperm nucleus then divides mitotically to form the endosperm, which is a tissue that provides food for the developing embryo.

The zygote is formed by the fusion of the egg cell with the first male gamete. The zygote then divides mitotically to form the embryo, which is the future plant.

The scutellum is a small, shield-shaped structure that is attached to the endosperm. It is derived from the cotyledons of the embryo, and it is responsible for absorbing nutrients from the endosperm and transporting them to the embryo.