Here's why:

* Formation: The aleurone layer develops from the endosperm, which is formed by the fusion of a sperm nucleus from the pollen grain with two polar nuclei of the central cell in the female gametophyte.

* Ploidy of Gametes: The sperm nucleus is haploid (n), and the polar nuclei are also haploid (n).

* Endosperm Ploidy: Therefore, the endosperm is triploid (n + n + n = 3n).

* Aleurone Development: The aleurone layer differentiates from the endosperm, inheriting its triploid ploidy.

This triploid nature of the aleurone layer is important for its function in seed germination. The aleurone cells synthesize and secrete enzymes (like α-amylase) that break down the stored starch in the endosperm, providing nutrients for the developing seedling.