Fertilization is the first stage in the process of establishing the reproductive system in plants. Here, a diploid zygote is formed when the female and male gametes combine to form one entity. A succession of post-fertilization activities takes place in the zygote, culminating in the formation of a seed.
Angiosperms are the most developed species of plant, consisting of flowers, stems, leaves, and roots, and are the most numerous. The flower serves as a vehicle for the transportation of seeds. The production of the seed takes place in the ovule from which a fruit develops, which is contained within the ovary that grows in flowers.
Following fertilisation, many changes take place in a plant’s reproductive system that results in the production of fruit (fruit development). The following are the four developmental stages that describe the changes that occur in a flower after fertilisation:
- Endosperm
- Embryogeny
- Seed
- Fruit
Embryonic Development of the Endosperm
The formation of an embryo is preceded by the development of the endosperm, a tissue that is present in the seed during fertilisation. It is possible to divide the development of endosperm into three categories:
The development of nuclei
The original endosperm nucleus undergoes successive nuclear divisions, resulting in the formation of a nuclear endosperm that does not have a wall.
Cellular formation
It is a process that occurs in cells. Following that, the formation of a cell wall begins from the periphery, and the formation of cellular endosperm takes place. For example, rice, coconut, maize, and so on.
The creation of helobial
Helobial formation is a type of intermediate endosperm formation that occurs between nuclear and cellular endosperm formation. Helobial formation is the name given to this type of intermediate endosperm formation.
The Endosperm’s primary function
- Endosperm tissue cells store starch as a source of energy and give metabolic support to embryonic development.
- The endosperm also provides mechanical support to the embryo and aids in the development of the embryo. In contrast, the endosperm of the seed is utilised by the seed during the germination process.
The Growth and Development of the Embryo
The term “embryogeny” refers to the process by which an embryo develops from a fertilised egg. This is the second post-fertilization incident that has occurred. Usually, after some endosperm formation, the zygote will begin to divide into two. In the beginning, the zygote grows into a pre-embryo, and later on, it evolves into a fully formed embryo.
The stages of embryogenesis in dicot and monocot plants are nearly identical. They do, however, differ in their organisational frameworks.
The embryo of the Dicot
The embryo of a dicot plant has one embryonal axis and two cotyledons, which are arranged in a spiral pattern. The epicotyl is the portion of the embryonal axis that is located above the cotyledon level, and the hypocotyl is the portion of the embryonal axis that is located below the cotyledon level. The hypocotyls terminate at the root tip, and the covering that covers the tip is referred to as the root cap.
The embryo of a Monocot
Monocot plants have only one cotyledon, which is known as the scutellum. The root cap is covered by a sheath that is homogeneous in appearance. The epicotyl is the portion of the embryonal axis that is located above the scutellum. Epicotyl contains a shoot apex as well as some leaf primordia known as coleoptiles, which are little leaf primordia.
Seed Research and Development
Typically, a seed has three distinct body parts.
Coating for Seeds
The seed coat is made up of two layers of integuments, which are responsible for its formation. The testa is the hard outer layer of the seed coat that protects the seed. Tegmen is the portion of the seed coat that is closest to the germ. A microscopic aperture on the seed coat, known as the micropyle, aids in the passage of water and oxygen within the seed.
Cotyledon
A seed contains one or two cotyledons, depending on the species. It is because of the storage of sustenance for the seed that these cotyledons are large and thick.
Axis of the Embryo
The embryonic root and shoot are referred to as the embryo axis when they are combined. The portion of this axis above the cotyledon develops into a shoot, while the portion below the cotyledon develops into a root.
Various Types of Seeds are Available
Monocotyledonous Seeds and Dicotyledonous Seeds are the two most common forms of seeds found in the plant kingdom, and they are both classified as such. As the name implies, these are the seeds that have only one cotyledon on the end of the seed. Cereal seeds, for example, are examples of this. Seeds with two cotyledons are known as dicotyledonous seeds. Castor seeds are a good illustration of this.
Conclusion
The ovary is responsible for the development of fruit through the processes of differentiation and cell division. The ovary wall grows and develops into the pericarp (which is the fruit wall). The pericarp of various fruits, such as guava, cucumber, and others, is fleshy. A leathery pericarp, on the other hand, can be found in pea, mustard, and other plants. The pericarp’s principal duty is to shield the seed from any injury that may occur throughout the growing process. It also aids in the dispersal of the seed.