Final answer:
In gymnosperms and angiosperms, a plant embryo packaged with a food supply in a tough coat is a seed, comprising an embryonic plant, nutritive tissue, and a seed coat.
Step-by-step explanation:
In gymnosperms and angiosperms, a plant embryo (young sporophyte) packaged with a food supply in a tough outer coat is a seed. A seed contains an embryonic sporophyte plant, a nutritive tissue, and a protective seed coat. The embryonic plant develops from a zygote formed by the union of egg and sperm, while the seed coat develops from sporophyte tissue of the parent plant known as integuments. Pollen grains, on the other hand, are male gametophytes which contain the plant's sperm and are quite distinct from the seed structure. In angiosperms, the endosperm serves as the food supply after the process of double fertilization, providing nourishment for the developing embryo.