This document describes the various stages of embryo development in angiosperms, using Capsella bursa-pastoris as an example. It discusses the polarization and first division of the zygote, the longitudinal and transverse divisions of the terminal cell that form the basic embryo structure, and the roles and divisions of the basal cell and suspensor. Subsequent stages including the quadrant, octant, globular, heart, torpedo and mature stages are summarized in detail.

1. Espino, Fermin, Paculan, Pajinag, Quesada

2. umanitoba.ca

3. bio.miami.edu

4.  To analyze and distinguish the different
stages of development in an angiosperm
embryo.
 To observe the stages of embryo
development in flowering plants.

5. weedecology.css.cornell
.edu
microscope-manufacturers.com
Capsella bursa fruit l.s.

7.  Zygote is highly polarized (Raghavan, 1997)
◦ Due to its orientation
◦ Due to its ultrastructural profile

8.  First division event in the zygote occuring
transversely to its long axis (Raghavan, 2006)
forming the:
◦ Basal cell – large, vacuolated, directed towards the
micropylar end; froms the suspensor
◦ Terminal cell – small, densely cytoplasmic, directed
towards the chalazal end; becomes the embryo
Planes of division of the terminal
cell and subsequent contributions
of the basal cell to the formation
of the embryo have led to a frame-
work of classification of embryos

9.  Terminal cell undergoes longitudinal division
◦ Crucifer (or Onagrad) type
◦ Asterad type
 Terminal cell undergoes transverse division
◦ Solanad type
◦ Caryophyllad type
◦ Chenopodiad type

11. apical cell
suspensor
basal cell
Capsella – following 1st division of zygote: 2-celled Capsella terminal cell divided longitudinally to produce 2-
proembryo: terminal cell and basal cell celled embryo proper
Taken from: Botanical Society of America (BSA) Taken from BSA
<http://secure.botany.org/plantimages/ImageData.asp?IDN <http://secure.botany.org/plantimages/ImageData.asp?IDN
=20-001> =20-003>

12.  The terminal cell divides longitudinally forming
two cells which again divide longitudinally
yielding a quadrant (4-celled).
 The quadrant divides transversely leading to the
octant (8-celled).
 The basal cell divides first, prior to the
terminal cell, once or occasionally twice
transversely.
 The cell closest to the terminal cell, the
suspensor cell divides transversely forming
a filament of seven to nine cells
(Raghavan, 2006).

13. quadrant
suspensor
basal cell
Capsella quadrant stage of embryo proper – 3
nuclei visible (out of 4)
Taken from: BSA <
http://secure.botany.org/plantimages/ImageData.
asp?IDN=20-004>

14. octant
suspensor
basal cell
Capsella octant stage (4 cells in plane of section, 4
additional cells behind)
Taken from: BSA
<http://secure.botany.org/plantimages/ImageDat
a.asp?IDN=20-005>

15.  The suspensor functions in the absorption
and short-distance translocation and
exchange of metabolites necessary for the
growth of the embryo (Raghavan, 1997).
 May have haustoria.
 Three Stages of the Suspensor
◦ (a) Octant Embryo – 6-celled
◦ (b) Globular Stage Embryo – maximum nuber of
cells attainede
◦ (c) Heart Stage Embryo – maximum length attained
and it grows out its genetically permissible life span

16. suspensor
suspensor
Suspensor of a heart stage Capsella embryo Suspensor of a heart stage Capsella embryo

17.  The octant embryo undergoes tangential division
forming a 16-celled embryo.
 The 8 peripheral cells of the 16-celled
proembryo become the protoderm and continue
to divide anticlinally.
 The ground meristem and procambium are
derived from the inner cells (the lower and upper
tier respectively).
 The cortex is formed from the peripheral layer of
cells of the inner core of 8.
 Procambium initiation starts at this stage as well
and occurs in the cells of the cortex or pith of the
globular embryo.

18.  The suspensor cell nearest the embryo
divides transversely providing the
hypophysis.
 The globular stage ends with an additional
three rounds of division mostly by the inner
core of cells.

19. suspensor
hypophysis
proembryo
protoderm suspensor
basal cell
Capsella – globular stage
Capsella – globular stage Taken from : BSA
<http://secure.botany.org/plantimages/ImageData.as
p?IDN=20-007>

20.  Lateral expansion of the distal poles of the
proembryo provide a bilateral symmetry and
forecast the imminent formation of the
cotyledons.
 Vertical division occurs twice to the
hypophyseal cells producing two layers of
four cells each (Raghavan, 2006).
 The shoot apical meristem is organized in a
depression between the growing cotyledons.

21.  Division and differentiation at the basal tier of
the embryo give rise to the hypocotyl.

22. initiating
cotyledons
protoderm
SAM
hypocotyl
hypophysis
suspensor
basal cell
Capsella – early cotyledons (heart-shaped or slightly
beyond)
Capsella heart shaped embryo Taken from : BSA
<http://secure.botany.org/plantimages/ImageData.asp?IDN
=20-009>

23.  Elongation of the hypocotyl and the
cotyledons give the embryo a torpedo shape.
 Shoot apical meristem is fully established and
appears as a mound or dome between the
cotyledons.
 Root apical meristem is established with the
root apex having a delimitation signifying the
progenitor of the embryonic radicle.
 Primary meristems already visible

24. protoderm
procambium
SAM
hypocotyl
RAM
Capsella – torpedo stage of embryo – cotyledons,
procambium present
Taken from: BSA
<http://secure.botany.org/plantimages/ImageData.asp?IDN
=20-011>

25.  Cotyledons curve
towards the
hypocotyl due to
space
restrictions
within the ovule.
 The tips of the
cotyledon
eventually reach
the tip of the
root pole.

26. SAM
procambium protoderm
cotyledons hypocotyl
RAM seed coat
root cap

27. protoderm
SAM
procambium
hypocotyl ground meristem
seed coat
cotyledons
root cap
RAM

28.  Plants, with special respect to angiosperms,
undergo different phases in its life cycle. One
of which is embryogenesis, the formation of a
multicellular embryo to a single-celled
zygote. This process involves various stages
in its development such as the globular,
heart, torpedo, and maturation stages which
are very critical to the growth of the plant.

29.  Raghavan, V. (1997). Molecular Embryology
of Flowering Plants. Cambridge University
Press. 40 West 20th St., New York, USA.
 Raghavan, V. (2006). Double Fertilization:
Embryo and Endosperm Development in
Flowering Plants. Springer-Verlag Berlin
Heidelberg. Leipzig, Germany.