The seeds of general plants are composed of three parts: seed coat, embryo and endosperm. The seed coat is the "armor" of the seed and acts as a protector of the seed. The embryo is the most important part of the seed, and it can develop into the roots, stems and leaves of the plant, and the endosperm is the place where the seed is concentrated.
Testa
The seed coat is developed from beads and has the function of protecting the embryo and endosperm. The seed coat structure of angiosperms is diverse, such as peanuts and other seeds have a hard peel on the outside, so the seed coat structure is simple, thin as paper; wheat, corn, rice, lettuce seeds, the peel and seed coat heal, when the seed matures the seed coat is squeezed and close to the inner layer of the peel. The structure of the seed coat is closely related to seed dormancy. Some plant seed coats contain germination inhibitors, so removing such plant seed coats has a stimulating effect on seed germination.
embryo
Embryos are formed from the development of fertilized eggs. A fully developed embryo consists of an embryo, a hypocotyl, cotyledons, and radicles.
The germ, located at the apex of the embryo, is the protozoite of the future plant stem-leaf system, which will develop into an aerial part of the plant in the future.
The hypocotyl is located between the germ and the radicle and is connected to the cotyledon, which later forms the part where the rhizome is connected.
The radicle is located under the hypocotyl, cone-shaped, is the prototype of the primary root in the seed, which can develop into the main root of the plant in the future, and is also the first to grow out of the cracked seed skin and form the root system of the plant.
Cotyledons are embryonic leaves, or temporary leaves, usually 1 or 2 pieces, located on the side of the hypocotyl. Among angiosperms, the embryo has 1 cotyledon, called a monocotyledonous plant (its nutrition mainly comes from endosperm). With 2 cotyledons, it is called dicotyledonous plants (its nutrition mainly comes from cotyledons). The embryos of gymnosperms have multiple cotyledons, such as 3 to 18 cotyledons of pinus.
endosperm
Endosperm is formed by the development of the fertilized polar nucleus. Endosperm is the tissue within the seed that stores nutrients and is rich in starch, fat and protein. Depending on whether there is endosperm in the seed. It is divided into two categories: endosperm seeds and endosperm seeds. In endosperm-free seeds, in the early stage of seed formation, the nutrients in the endosperm are absorbed by the embryo and transferred to the cotyledons for storage, so the endosperm disappears after the seed matures, and the cotyledons are particularly hypertrophied, such as peanut seeds, because the embryos in the development process, the endosperm of the seeds is sucked out, so there is no endosperm in the seed (the cotyledon plays the role of endosperm).