What substances are plant seeds made of?

Seeds are the first stage of a plant’s life cycle. Protected inside the hard seed layer, it is a baby plant called an embryo. Food that fuels germination and growth is either packed around the embryo or stored in special seed leaves called cotyledons.

Most plants grow from seeds. These seed plants are classified into two groups: angiosperms and gymnosperms. Angiosperms are flowering plants. Their seeds develop inside the female reproductive part of the flower called the ovary. Gymnosperms (conifers, ginkgoes, and cicadas) do not have flowers or ovaries. Their seeds ripen inside the cones. Seeds can be carried away from the parent plant by wind, water, or animals.