EMBRYONIC DEVELOPMENT IN SPERMATOPHYTES: CHARACTERISTICS - BIOLOGY - 2025

The embryonic development of spermatophytes takes place after the formation of the zygote, after the process of fertilization of these vascular plants. Spermatophytes are plants that produce seeds and reproduce through spores; that is the origin of its name.

The spores are haploid cells; that is, they contain only half of the total chromosomes of the species. These sex cells originate through cell divisions within the sporangium, leading to the production of gametophytes.

In turn, the union of two gametophytes forms the zygote with a complete chromosome charge, which later becomes the embryo of the new plant.

Two types of spermatophyte plants are distinguished: gymnosperms and angiosperms. Depending on the type of plant, embryonic development is different.

Embryonic development in gymnosperm spermatophytes

Gymnosperms do not have flowers. Consequently, the seeds are visible from the outside, since they are not enclosed by fruits.

Once the pollen grain is introduced into the female reproductive system, it develops a pollen tube to facilitate access to the female gametophyte and lead to fertilization.

Fertilization occurs when the pollen grain (male gametophyte) releases sperm cells that fertilize the egg cell, located in the nucleus of the egg (female gametophyte).

Then, the zygote is formed by the union of the two gametophytes, during the phase of development called sporophyte. Subsequently, mitosis takes place; that is, the equitable division of hereditary material (DNA), to give rise to the embryo.

The female gametophyte covers the embryo and becomes part of the nutritive material that makes up the mature seed.

Next, the integument is formed, which is a plant tissue that protects the seed. The integument borders the embryo and nutritional material during the early stages of development.

When the female organ opens, the mature seeds are released into the environment. The wind disperses the seeds and, if they fall on fertile soil and with suitable climatic conditions, they germinate, creating new gymnosperms.

Embryonic development in angiosperm spermatophytes

They are spermatophyte plants with flowers. In contrast to gymnosperms, the seeds of angiosperms are not visible from the outside, as they are located inside a fruit.

The presence of the flowers considerably modifies the reproductive process. The gynoecium, which is the female part of the plant, is made up of the pistils, which are made up of the carpels.

The carpels, in turn, are formed by the ovary, style and stigma of the flowers.

Pollen is transferred to the flower stigma thanks to the action of different means of transport: wind, water, and even the transfer of pollen through insects.

Pollen is deposited on the surface of the flower stigma and germinates, dividing into two male gametes.

Both gametes travel through the pollen tube that grows along the stigma, until they fertilize the reproductive ovum within the ovary.

The fertilized ovum goes through a series of mitotic divisions to form the embryo, which is completely covered by the seed. Later, the ovary enlarges and matures, giving rise to the fruit, which encloses the seeds inside.

This characteristic means that the embryo is protected from dehydration and possible mechanical damage during its development, since the nucela of the original ovule (layer that covers the embryo sac) provides all the nutritional resources for the development of the embryo.

References

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2. Spermatophytes (2014). Science and Development Magazine. Mexico DF, Mexico. Recovered from: cyd.conacyt.gob.mx
3. González, C. (2016). Spermatophytes. Botanical Laboratory of the National College of Buenos Aires. Buenos Aires, Argentina. Recovered from: botanica.cnba.uba.ar
4. Vascular Seed Plants (Spermatophytes): The Angiosperms. El Paso Community College. Texas, USA. Recovered from: epcc.edu
5. Wikipedia, The Free Encyclopedia (2017). Angiospermae. Recovered from: es.wikipedia.org
6. Wikipedia, The Free Encyclopedia (2017). Spermatophyta. Recovered from: es.wikipedia.org