Plant embryonic development

[2] However, both plants and animals including humans, pass through a phylotypic stage that evolved independently[3] and that causes a developmental constraint limiting morphological diversification.

[4][5][6][7] Embryogenesis occurs naturally as a result of single, or double fertilization, of the ovule, giving rise to two distinct structures: the plant embryo and the endosperm which go on to develop into a seed.

The last domain, the suspensor, is the region at the very bottom, which connects the embryo to the endosperm for nutritional purposes.

The important aspect of this stage is the introduction of the protoderm, which is meristematic tissue that will give rise to the epidermis.

The important component of the globular phase is the introduction of the rest of the primary meristematic tissue.

According to Evert and Eichhorn, the heart stage is a transition period where the cotyledons finally start to form and elongate.

[14] The suspensor complex is shortened because at this point in development most of the nutrition from the endosperm has been utilized, and there must be space for the mature embryo.

Dormancy is a period in which a seed cannot germinate, even under optimal environmental conditions, until a specific requirement is met.

This process exposes the seed to certain environmental conditions, like cold or smoke, to break dormancy and initiate germination.

Research has shown that the hypocotyl from both gymnosperms and angiosperms show auxin transport to the root end of the embryo.

[18] They hypothesized that the embryonic pattern is regulated by the auxin transport mechanism and the polar positioning of cells within the ovule.

Further auxin transport inhibition research, conducted on Brassica juncea, shows that after germination, the cotyledons were fused and not two separate structures.

Applications of this process include: clonal propagation of genetically uniform plant material; elimination of viruses; provision of source tissue for genetic transformation; generation of whole plants from single cells called protoplasts; development of synthetic seed technology.

The process of androgenesis allows a mature plant embryo to form from a reduced, or immature, pollen grain.

[20] However, once the vegetative cell starts to make starch and proteins, androgenesis can no longer occur.

The first phase is the acquisition of embryonic potential, which is the repression of gametophyte formation, so that the differentiation of cells can occur.

Then during the initiation of cell divisions, multicellular structures begin to form, which are contained by the exine wall.

After these three phases occur, the rest of the process falls in line with the standard embryogenesis events.