Why does the zygote begin to divide only after the division of Primary endosperm cell (PEC)?

The zygote begins to divide only after the division of Primary endosperm cell (PEC) because of the following reasons:

i. Zygote needs nourishment during its development.

ii. The primary endosperm cell (PEC) forms the endosperm where food materials are stored for the developing embryo.

iii. A mature, fertilised embryo sac offers very little nourishment to the zygote.

iii. PEC divides and generates the endosperm tissue which nourishes the zygote.

So the zygote begins to divide only after the division of Primary endosperm cell (PEC) is an adaptation to provide assured nutrition to the developing embryo.