Endosperm provides nutrients to the embryo as it contains

The endosperm provides nutrients to the embryo as it contains Hormones, Vitamins and Enzymes.
The endosperm is a tissue produced inside the seeds of most flowering plants following double fertilization.
It is triploid in most species, which may be auxin-driven. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein.