The process of seed germination is as follows: seeds begin to germinate under suitable environmental conditions. When the seed germinates, it absorbs water and expands, the seed coat becomes soft, and the respiratory function is gradually enhanced. Nutrients stored in cotyledons or endosperm are gradually decomposed and transformed into nutrients that can be absorbed and utilized by cells, and then transported to embryos, hypocotyls and radicles.
The radicle of the seed first breaks through the seed coat and grows to the ground, and then develops into the root of the seedling. Subsequently, the cells of hypocotyl also grow and elongate, and develop into the junction of root and stem, and the embryo develops into the stem and leaf of seedling. At the same time, the endosperm or cotyledons storing nutrients gradually shrink due to the consumption of nutrients, which indicates that embryos are the structure of developing seedlings.
The endosperm-free seeds of dicotyledonous plants, such as soybean, cotton and various melons, germinate with the radicle extending into the soil to form the main root, and then the hypocotyl elongates to push the cotyledons and embryos out of the soil. The cotyledons of this seedling were unearthed. The main shaft of seedlings under cotyledons extends from hypocotyl; The main axis between the cotyledon and the first true leaf is formed by the epicotyl. Cotyledons usually turn green after being unearthed, so they can temporarily carry out photosynthesis. Later, the germ developed into stems and real leaves on the ground. Nutrients in cotyledons will wither and fall off when they are exhausted.
The endosperm seeds of dicotyledonous plants such as pea, litchi and orange, and the endosperm seeds of clover rubber seeds, while the endosperm seeds of monocotyledonous plants such as rice, wheat and corn germinate, the hypocotyl does not elongate and the cotyledons remain in the soil. Epicotyl or mesocotyl and embryo protrude from the surface.