Early Development of the Plant Body
Chapter 22
True or False
1) Embryogenesis is the formation of an
embryo.
2) 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.
Proembryos
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.
– Ground meristem- 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
• Apical Meristem- 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.
The stored food occurs in the cotyledons.
The stored food occurs in the endosperm.
The stored food occurs in the endosperm.
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.