User:Dylandubay1/Plant embryonic development

Two cell stage[edit]
Following fertilization, the zygote and endosperm are present within the ovule, as seen in stage I of the illustration on this page. Then the zygote undergoes an asymmetric transverse cell division that gives rise to two cells - a small apical cell resting above a large basal cell. These two cells are very different, and give rise to different structures, establishing polarity in the embryo. '''Apical cell division occurs more rapidly than basal cell division, as the apical cell will become the embryo. '''

Globular stage[edit]
The name of this stage is indicative of the embryo's appearance at this point in embryogenesis; it is spherical or globular. Stage III, in the photograph above, depicts what the embryo looks like during the globular stage. 1 is indicating the location of the endosperm. The important component of the globular phase is the introduction of the rest of the primary meristematic tissue. The protoderm was already introduced during the sixteen cell stage. According to Evert and Eichhorn, the ground meristem and procambium are initiated during the globular stage. The ground meristem will go on to form the ground tissue, which includes the pith and cortex. The procambium will eventually form the vascular tissue, which includes the xylem and phloem. '''In this stage, the suspensor differentiates and forms a column of single or multiple cells. In monocotyledons, the suspensor does not undergo as much differentiation and does not produce a column of single or multiple cells.'''

Embryonic Development in Monocots
Early embryonic development in monocots is similar to dicots, although the mature seed of monocots is more structurally complex than dicots. The following morphogenic events are unique to monocots;

Pre-embryo stages: After fertilization of the zygote, it will undergo asymmetrical cell division by mitosis. This cell division results in two cells; The apical and the basal cells.

Apical Cell: The apical cell will lead to the development of the embryo, thus it divides more rapidly than the basal cell. The apical cell gives rise to the quadrant (4-cell), octant (8-cell), and dermatogen stages. The suspensor cells are produced from the apical cell, excluding the terminal suspensor cell.

Basal Cell: The basal cell does not divide. Instead, it enlarges into a vesicular cell and forms the terminal cell of the suspensor.

Transition Stage: The transition stage gives rise to the coleoptile and the scutellum from the adaxial and abaxial regions, respectively. The coleoptile acts as a sheath that protects the newly developing leaf primordia and the growing stems. The scutellum is the term for the cotyledon in monocots, which is connected directly to the embryo. In contrast to dicots, the phylotypic stage of embryogenesis occurs in the transition stage.

Early, Middle, and Late Leaf Stages:

In early leaf stage, the shoot apical meristem forms between the scutellum and the suspensor. The coleoptile enlarges as the leaf primordium begins to develop. Following this, differentiation of the root apical meristem cells and the coleorhiza cells occurs. The coleorhiza acts as a sheath that protects the developing roots.

During the middle leaf stage, the leaf primordium and shoot apical meristem become completely surrounded by the developing coleoptile.

In the late stage, the epiblast emerges from between the coleoptile and coleorhiza and has fan-shaped morphology. Throughout all stages of the leaf development, the scutellum significantly expands, which is understood to be important in the transfer of nutrients in the embryo.

Maturation: Maturation occurs when each internal organ has differentiated, although growth from the shoot and root meristems continue.

=== During early embryonic development in both Monocots and Eudicots, addition of new cells are gradually added to the apical meristem of the shoot and root. In monocots, the apical meristem grows on one side of the cotyledon and becomes fully coated by a sheath-like extension from the base of the cotyledon. ===