Polarity of Plant Development Flashcards
(1) After fertilisation, the Arabidopsis zygote is already polarised, with the apical end of the cell being more ___, with more ___ present at the basal end.
(2) The first division of the Arabidopsis zygote is
___. The zygote undergoes an asymmetric
division to produce an apical cell which will give rise to-the ___ of the embryo proper, and a basal cell which gives rise to the ____ connecting the embryo and maternal tissues.
cytoplasmically dense
vacuoles
asymmetric
bulk
suspensor
construction of the Arabidopsis body during embryogenesis
4) ____ stage. Transverse divisions
produce a single outer layer of cells. This outer
layer is termed the ___ and will
give rise to the ____ of the plant.
4) Dermatogen stage.
protoderm
epidermis
construction of the Arabidopsis body plan during embryogenesis
(5) ___ stage embryo. Continued radial
divisions give rise to the central vascular
initials within the body of the developing
embryo. A lens shaped cell derived from the
upper portion of the suspensor cell file divides
to give rise to the central cells of the root apex.
6) ___ stage embryo. ___ of cells in
the upper half of the embryo gives rise to
_____. This is the first appearance of bilateral symmetry.
Globular
Heart
Proliferation
cotyledon primordia
construction of the Arabidopsis body plant during embryogenesis 
7) Further cell divisions produce the
“____” stage embryo with further elaboration of the root and shoot apices and growth of the cotyledons.
8) After ten days, the embryo consists of about
20,000 cells, is about 0.5 mm in length and has
developed a body plan similar in miniature to
that of the Arabidopsis seedling. The embryo is
converted to a quiescent state and is
desiccated prior to seed dispersal. After seed
dispersal and germination, development of the
embryo is reactivated.
torpedo
summary of construction of the Arabidopsis body during embryogenesis (8)
- Polarity establishment: Arabidopsis zygote is already polarized, with denser cytoplasm at the apical end and more vacuoles at the basal end.
- Asymmetric Division: Zygote divides into an apical cell, forming most of the embryo, and a basal cell, forming the suspensor.
- Early development: : Embryo divides to form a radially symmetric ball of 2, 4, and then 8 cells above the suspensor, while the suspensor also continues to divide longitudinally.
- Dermatogen Stage: Transverse divisions form a single outer layer of cells called the protoderm, which becomes the plant’s epidermis.
- Globular Stage:Continued radial divisions form central vascular initials and the root apex cells.
- Heart Stage: Cell proliferation in the upper half forms cotyledon primordia, showing bilateral symmetry.
- Torpedo Stage: Further divisions develop shoot and root apices, and cotyledons grow.
- Quiscent (Maturation): After ten days, embryo has about 20,000 cells, is 0.5 mm long, resembling a miniature Arabidopsis seedling. It becomes quiescent and desiccated for seed dispersal.
THE MAJOR CHALLENGES OF EMBRYOGENESIS ARE
- To establish the ____. Radial patterning produces ____, and axial patterning establishes the _____.
- To set aside ____ for postembryonic elaboration of the body structure (leaves, roots, flowers, etc.).
- To establish an accessible ____ for the
germinating embryo until it becomes autotrophic.
- basic body plan
three tissue systems
apical-basal (shoot-root) axis - meristematic tissue
- food reserve
established in the first cell division following
fertilization. The establishment of polarity has been investigated using brown algae as a model system
Polarity
Adult plant growth is due to the activity of ___
established during embryogenesis.
Meristems are organised cellular structures capable of indeterminate growth contains an organised core of undifferentiated “___” which can divide and
differentiate to produce adult tissues, while maintaining and regenerating the meristem.
meristems
stem cells
Classification of Meristem origin
Promeristem
Primary meristem
Secondary meristem
Classification of Meristem LOCATIOM
Apical meristem
Intercalary meristem
Lateral meristem
Classification of Meristem
Plane of Division
Mass meristem
Plate meristem
Rib meristem
PLANES OF CELL CLEAVAGE
- ___ cell divisions are the ones
that occur parallel to the tissue or
organ surface resulting to rows of
cells stacked one over the other.
Periclinal
PLANES OF CELL CLEAVAGE
In ____ cell divisions, there is
cleavage at right angles to the tissue or
organ surface resulting to columns of
cells adjacent to one another
Anticlinal
____ - straight line about which a
body or a geometric figure rotates
____ establishes the apical- basal (shoot-root) axis, embryonal axis divides the embryo or immature plant into regions by the help of embryonal
axis region.
Plant axis
Axial patterning
___ are functional repetitive units
of a plant, continually produced by root
and shoot meristems throughout a plant’s
vegetative life-cycle
Phytomers
