Early Development of the Plant Body Chapter 22
True or False • Embryogenesis is the formation of an embryo. • The developing embryo in angiosperms is photosynthetic.
Embryogenesis • Embryogenesis- formation of an embryo. • The first two divisions are transverse and establish embryo polarity. • Upper Pole- chalazal pole. • Consists of an apical cell that gives rise to an embryo proper, which will eventually give rise to the mature embryo. • Lower Pole- micropylar pole. • Consists of a basal cell that gives rise to a suspensor. • Establishment of polarity fixes the structural axis on which the lateral appendages will be later arranged.
Embryo Proper and the Primary Meristems • The embryo proper is tissue that differentiates to form 3 primary meristems. • Primary Meristems • Protoderm- forms the epidermis of the plant by periclinal divisions of the outer cells of embryo proper. • Procambium- forms the vascular tissue of the plant by vertical divisions. • Groundmeristem- forms the ground tissue of the plant by vertical divisions.
The apical meristem in angiosperms ___________________________. A) is a region of tissue at the tip of shoots and roots that is responsible for programmed cell death. B) is a region of tissue at the tip of shoots and roots that forms new cells. C) coordinates hormone production much like the brain in mammals D) produces the bark we see on trees E) none of the above
Apical Meristems • ApicalMeristem- regions of tissue at the tip of shoots and roots that forms new cells. • As the embryo matures new cell formation gradually becomes restricted to the apical meristems. • Shoot Apical Meristem- positioned between the two embryonic leaves in eudicots and lateral in monocots. • Radicle- embryonic root.
Seed Terms • Hypocotyl- stemlike axis below the cotyledons. • Hypocotyl-root axis- an undistinguished radicle. • Epicotyl- stemlike axis above the cotyledons. • Plumule- the first bud of an embryonic shoot. • Pericarp- the fruit wall, which develops from the wall of the ovary.
Which of the following effects seed germination? A) water B) oxygen C) light and temperature D) hormones E) all of the above
Seed Germination • Dependent on external and internal factors. • External (Environmental) • Water • Oxygen • Temperature • Light • Internal (Biological) • Hormones- gibberellins. • Epigeous- cotyledon/s are carried above ground level. • Hypogeous- cotyledon/s remain underground.
True or False The onion has an epigeous type of seed germination.