Chapter 22 (Raven) Flashcards
How is polarity important in embryonic development of plants?
essential first step, because it fixes the structural axis of the body (“backbone”) on which the lateral appendages will be arranged.
What are the three primary meristems of plants and which tissues do they form?
- protoderm forms the dermal tissue system
- procambium forms the vascular system
- ground meristem forms the ground tissue system
Through what stages do embryos of eudicots develop? How does embryo development in monocots differ from that in eudicots?
- globular stage (no development of cotyledons)
- heart stage (monocots form only one cotyledon and become cylindrical instead)
- torpedo stage (elongation of cotyledon and primary meristems) (in monocots, the cotyledon often looks like the dominating structure due to size.)
4.
What are the main parts of a mature monocot or eudicot embryo?
it consists of an axis bearing one or two cotyledons. (in flowering plants) the shoot and root apical meristems are at opposite ends. epicotyl with a plumule, hypocotyl below the cotyledons, radicle below the hypocotyl.
What phenomena, or processes, characterize seed maturation, the second phase of seed development?
build up of stored food, dessication occurs, and seed coat hardens.
Of what significance is seed dormancy to the plant?
ensures that the conditions will be favorable when growth does occur, allows passage of seeds through the digestive tract of some animals, and are closely linked to the ecological conditions in their particular habitats.
What are the two phases of seed development?
embryogenesis and seed maturation
What is embryogenesis?
it establishes the body plant of the plant, by two superimposed patterns: apical-basal pattern and radial pattern.
What is the apical-basal pattern in embryogenesis?
it is the first three stages of embryo development, where the seed is dividing into two cells (apical and basal, asymmetrically), then three (basal remains, apical divides again), then proliferates.
What is the radial pattern in embryogenesis?
it refers to concentrically arranged tissue systems.
What is the name of the upper pole in plant polarity?
the chalazal
What is the name of the lower pole in plant polarity?
the micropylar
What names does the seed go through as it develops?
- one and two celled zygote
- three celled proembryo
- four celled proembryo
- embryo proper with formation of the protoderm (2 celled suspensor at bottom)
- embryo proper forms a notch, all three meristems present, suspensor present and mature
- embryo is mature, with all typical parts, and the suspensor is gone.
How is the protoderm formed?
by periclinal divisions (divisions parallel to the surface)
the ground and procambium meristems are formed by…
vertical divisions within the embryo
in angiosperms, the apical meristem arises between the…
cotyledons, or on one side of the cotyledon, in the case of monocots. in monocots, its also surrounded by a sheathlike extension from the base of the cotyledon.
True or False. the suspensor of angiosperms is metabolically active.
True.
the suspensor goes through programmed cell death during which stage?
the torpedo stage.
True or False. the embryo transmits inhibitory signals to the suspensor to keep it from developing into an embryo.
True.
If a radicle cannot be distinguished, the embryonic axis below the cotyledon is referred to as…
the hypocotyl-root axis.
What is the first structure to immerge from most seeds?
the root (or radicle) called the primary root or taproot.
What are the branches of the primary root called?
lateral roots.
In monocots, the primary root is…
shortlived.
How do monocots form roots after the loss of the primary root?
they form stem-borne roots which arise at the nodes and then produce lateral roots.
What is the difference between epigeous or hypogeous seed germination?
in epigeous germination, the cotyledons extend above ground. With hypogeous germination, they remain below ground.
What does it mean when a seed is established?
it no longer depends on the stored food of the seed for nourishment, it is a photosynthesizing, autotrophic organism, and the seedling phase has come to an end.
