4.6.6: Chapter Summary

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Melissa Ha, Maria Morrow, & Kammy Algiers
Yuba College, College of the Redwoods, & Ventura College via ASCCC Open Educational Resources Initiative

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During embryogenesis (the development of the embryo), the proembryo develops into the embryo proper and finally into the mature embryo. The mature embryo is surrounded by the seed coat. Depending on the species, nutrient-rich endosperm may remain in the mature seed between the embryo and seed coat. The embryo consists of the cotyledon(s) and embryonic axis, consisting of the epicotyl and hypocotyl. The young root is called the radicle. Monocot seeds differ from eudicot seeds in that they contain a single cotyledon (scutellum) and protective sheaths surrounding the young shoot and root, the coleoptile and coleorrhiza, respectively.

Cell division and growth are concentrated at meristems. The shoot apical meristem and root apical meristem produce three primary meristems: the protoderm, ground meristem, and procambium. The cork cambium and vascular cambium are secondary meristems, which allow woody plants to increase in girth.

The embryo then remains dormant until germination. Various environmental conditions such as proper temperature, light, and water may be required for germination depending on the species. Germination may be epigeous, in which cotyledon(s) rise above the ground, or hypogeous, in which cotyledon(s) remain belowground.

Rapid cell division at the shoot apical meristem initiates shoot development, but growth also occurs in the internodes throughout the shoot. Floral meristems develop from shoot apical meristems, and floral structure is controlled by the ABCDE model.

After completing this chapter, you should be able to...

Explain the steps of embryogensis in eudicots.
Compare embryogenesis in eudicots versus monocots.
Define and locate the two apical meristems and the three primary meristems.
Locate the major seed structures and identify the function of each.
Compare eudicot and monocot seeds.
Identify the environmental factors that stimulate germination.
Distinguish between epigeous and hypogeous germination.
Compare germination in eudicots versus monocots.
Define the roles of the shoot apical meristem, leaf primordia, intercalary meristems, and axillary buds in shoot development.
Explain the mechanism of the ABCDE model of floral development.

Attribution

Melissa Ha (CC-BY-NC)