Plant embryonic development

Lore & Background

Following fertilization, the zygote and endosperm are present within the ovule. The zygote undergoes an asymmetric transverse cell division, producing a small apical cell and a large basal cell. The apical cell gives rise to the hypocotyl, shoot apical meristem, and cotyledons, while the basal cell gives rise to the hypophysis and the suspensor. After two rounds of longitudinal division and one round of transverse division, an eight-celled embryo forms, with four distinct domains: apical embryo domain, central embryo domain, basal embryo domain, and suspensor.

Reader's Guide

Plant embryonic development is significant because it establishes the basic cellular pattern necessary for the shoot-root axis and primary tissue layers. The process includes stages such as the eight-cell stage, sixteen-cell stage (where protoderm is introduced), globular stage (where ground meristem and procambium are initiated), heart stage (where cotyledons form and symmetry shifts from radial to bilateral), and proembryo stage (involving programmed cell death of the suspensor). Maturation involves cell growth and storage of macromolecules, followed by dormancy. Auxin plays a key role in establishing polarity and regulating embryonic pattern. Somatic embryogenesis offers an alternative form, producing embryos from ordinary plant tissue without endosperm or seed coat.

Did You Know?

• Unlike animal embryonic development, plant embryonic development results in an immature form lacking leaves, stems, and reproductive structures.
• Both plants and animals pass through a phylotypic stage that evolved independently and limits morphological diversification.
• Auxin transport inhibitors prevent carrot embryos from progressing to later stages, causing continued spherical expansion or fused cotyledons.
• The suspensor complex reaches peak size in the globular stage and is later terminated via programmed cell death.