Development of seed

A seed is an embryonic plant that has a protective coat around it. Seed development is a stage in the reproduction of spermatophytes (seed plants), such as gymnosperms and angiosperms. After pollen fertilisation and some growth within the mother plant, the mature ovule produces seeds. The zygote produces the embryo, while the integuments of the ovule produce the seed coat. 

Seed development:

Angiosperm:

Angiosperm (flowering plant) seeds are made up of three genetically separate components: 

1. the embryo generated from the zygote,
2. the typically triploid endosperm, and
3. the seed coat made up of tissue derived from the ovule’s maternal tissue.

The formation of the primary endosperm and the zygote in angiosperms begins with double fertilisation, which involves the fusing of two male gametes with the egg cell and the central cell to generate the primary endosperm and zygote. Until the roots have developed following germination, this tissue becomes the food for the newborn plant. 

Ovule:

The ovules grow into seeds after fertilisation. The ovule is made up of several components:

1. At the pericarp, the funicle (funiculus, funiculi) or seed stalk connects the ovule to the placenta and thus the ovary or fruit wall.
2. The nucellus is the major part of the ovule where the megagametophyte develops, as well as the remains of the megasporangium.
3. The micropyle is a small pore or opening in the apex of the ovule’s integument where the pollen tube normally enters during the fertilisation process.
4. The chalaza connects the integument and nucellus at the base of the ovule, opposite the micropyle. 

Embryo:

The embryo’s basic components are:

1. The embryonic axis is linked to the cotyledons, or seed leaves. There could be one (Monocotyledons) or two (Monocotyledons) (Dicotyledons).
2. The epicotyl is the embryonic axis above the cotyledon’s attachment point. 
3. The plumule, the epicotyl’s tip, has a feathery look due to the presence of immature leaf primordia at the apex, and when germination occurs, it will become the stem.
4. The stem-root transition zone is formed by the hypocotyl, an embryonic axis connecting the epicotyl and the radicle below the point of attachment of the cotyledons.
5. The radicle, which is the hypocotyl’s basal tip, develops into the major root. 

Seed coat: 

The integuments of the growing ovule undergo significant alterations, most commonly a decrease and disarray, but occasionally a thickening. The two integuments or outer layers of cells of the ovule, which arise from tissue from the mother plant, form the seed coat, with the inner integument forming the tegmen and the outer integument forming the testa. When the seed coat is made up of only one layer, it is called the testa; however, not all testae are homologous from one species to the next. 

Gymnosperms:

The ovules and thus the seeds are exposed in gymnosperms, which do not have ovaries. Their nomenclature is based on this – naked seeded plants. The seed is not developed by double fertilisation when two sperm cells are transported from the pollen, but one sperm nucleus connects with the egg nucleus and the other sperm is not utilised. One zygote is sometimes aborted or absorbed during early development after each sperm fertilises an egg cell. 

Development of rice seed:

Plant development begins with the fertilisation of an egg cell with a sperm nucleus to form a zygote (fertilised egg). Plant development progresses toward maturity through a variety of stages that are identifiable based on landmark events, beginning with the first zygotic division. The production of male and female gametes, which fertilise to produce a zygote, is the ultimate stage of development. The embryonic, vegetative, and reproductive phases of plant development are typically divided into three parts. 

Development of seed habit:

The character of spermatophytes is seed, which is an ovule generated following fertilisation. Seed habit refers to the adaptation of heterospory as well as the preservation and germination of a single megaspore within a megasporangium. It is generally thought to be the most advanced and successful mode of sexual reproduction used by terrestrial plants. 

Conclusion:

Seeds have been a significant advancement in the reproduction and success of vegetable gymnosperm and angiosperm plants, as opposed to more primitive plants like ferns, mosses, and liverworts, which do not contain seeds and rely on water for propagation. In both hot and cold climes, seed plants currently dominate biological niches on land, from forests to grasslands.