The seed coat is the hard or semi-hard coating that protects the seed from numerous insects and illnesses, according to botany. Seed coverings also keep extra water from reaching the seed, preventing it from germinating prematurely.

Harder shells help protect the seed from mechanical stress and humidity variations. The seed coat also serves as a barrier between the developing seed and the surrounding environment.

The plant’s maternal tissue, such as the ovule and integuments, produce seed coverings. The seed coat of mature seeds, such as peanuts, can be incredibly thin and brittle. Coconut, honey locusts, and other seeds, on the other hand, have a much harder seed covering. The majority of botanists distinguish between two types of seed coats: unitegmic and bitegmic.

Although the seed coat develops from the ovule, it may not be visible right away in angiosperms because the seed is encased in a pericarp of a fruit wall. The seed coat of corn kernels, for example, is the visible component that protrudes from the surface. The tegmen, which is fragile, and the testa, which is thicker and harder, are the two primary layers of seed coverings.

Structure of the seed coat:

• The seed coat is divided into two layers: the testa on the outside and the tegmen on the inside.
• The testa is often thick and leathery, but the tegmen is normally thin, papery, and fused to the testa. Untegmic ovules (ovules with only one integument) produce seeds with a single-layered seed coat. The seed coat’s purpose is to protect the vulnerable embryo.
• A slender stalk called the seed stalk or funiculus keeps the seed adhering to the pericarp. A little oval depression called hilum represents the location of the seed stalk in a ripe seed.
• The micropyle is a tiny pore located just below the hilum. The stalk is united with the seed coat in certain seeds, and the fused section shows as a tiny ridge slightly above the hilum. The raphe is the name given to this ridge.

Embryo 

Seeds are merely containers, and not all plants reproduce by using them, even though we frequently think of them as the beginning of new plant life. The foundations of new plant life, like those of animals, have less to do with the container, whether it’s an egg or a womb, and more to do with what’s within that container: the embryo. Whether contained in a seed or a bud, the embryo in plants contains the early form of the organs the plant requires to survive. When conditions are correct, the embryo breaks out of its container and becomes a seedling — beginning the process of developing into an adult plant.

Embryo Development in Plants

• When a plant is fertilised, the male and female cells join to produce a zygote, which can divide and mature into a new creature. The parent plant protects the zygote by developing a container around it, whether it’s a seed, a bud, a stem, or anything else, that’s packed with endosperm
• sustenance for the embryo throughout the early stages of germination. The embryo can then fulfil its role when this container is exposed to the proper environment.

The Function of Plant Embryos

The role of the plant embryo is to act as a “starting kit” for the future plant’s life: It includes the earliest forms of the plant’s roots, leaves, and stem, and it can sense whether the right circumstances for growth are available, frequently through the usage of its container. When the embryo senses enough water, oxygen, and other minerals in its surroundings, it begins to devour the endosperm in its container, allowing the new plant to grow.

Plants from Seeds

Germination is the first important stage of plant development. When an embryo in a container has grown large enough, it breaks out of its container, devouring endosperm for energy and taking water and oxygen from its surroundings. The new plant’s stem and leaves emerge from the earth, and roots begin to grow. The embryo is formally referred to as a “seedling” once it has burst from its container and will grow into an adult plant.

Conclusion :

The seed coat not only has developed very sophisticated procedures for protecting embryos and germinating seedlings from biotic and abiotic stressors, but it also plays a key role in developmental regulation. The capacity to modify any of these processes using cloned genes has the potential to drastically change seed yield and composition for traditional purposes as well as the generation of novel products for new uses. We have attempted to synthesise our knowledge of seed coat structure, composition, and genetics in this paper. Our understanding of the genes that control seed coat growth or the pathways that create their beneficial chemicals is woefully inadequate at this moment to achieve biotechnology’s full promise. However, many of the biological tools needed for biotechnology are well developed. Although Arabidopsis is an essential model species that may help us learn more quickly, it may not be enough to give information relevant to many of our crops. A more fundamental study on the seed coat is needed since it is a unique and intriguing developmental system that has been overlooked for far too long.