Why do Fagales seeds have large embryos and little or no endosperm?

In the plant order Fagales, the seeds are characterized by having a large embryo and little or no endosperm because the reserve materials typically stored in the endosperm are instead transferred to and stored within the embryo itself, specifically in the cotyledons (seed leaves).123

While many flowering plants rely on endosperm—a triploid nutrient tissue formed during double fertilization—to support the developing embryo, this process varies across species. In cases where endosperm is reduced or absent, the embryo becomes the primary site for nutrient storage, ensuring the seedling has the necessary resources for growth upon germination. This developmental strategy is common in various plant groups where the growing embryo consumes the endosperm before the seed reaches maturity.134