1. Lecture #2
The Development of the Plant body

2. Parts of a flower
The four kinds of
floral organs are
the sepals,
petals, stamens,
and carpels.
 epals and petals are
S
nonreproductive organs.
 tamens and carpels
S
are the male and female
reproductive organs,
respectively.

3. The stamen
 he microsporangia/pollen
T
sacs contain the pollen grains
 made up of
anther and filament

4. The stamen: tissue differentiation
endothecium
10 parietal layer
**middle layer
Tapetum
Archesporial * (nourishment of the developing
PMC)
layer
Meiosis***
10 sporogenous Micro microspores
tissue sporocytes
*periclinal division
**in eudicots originate from outer parietal layer; in monocots from inner parietal layer
***cytokinesis is usually simultaneous in dicots and successive in monocots

5. Illustration of a new models for plant archesporial initiation in the
ovule and anther.
Cells colored in red, blue, yellow, magenta, orange and green
indicate archesporial cells, sporogenous cells (sc), primary
parietal cells, tapetal cells, middle layer cells and endothecium
cells, respectively.

8. Development of male gametophyte

9. The ovule
 onsists of the:
C chalaza
nucellus
 nucellus – the
megasporangium
 integuments
 uniculus – the stalk
f
 halaza- the region where
c
the integuments fuse micropyle
with the funiculus

10. Megasporogenesis
Sporogeous cell
Archesporial cell
Parietal cell
meiosis
10 sporogenous Megaspore 4 Megaspores
cell mother cell
(3 degenerate)

13. Pollination and Fertilization
Pollination – is the transfer of the pollen
to the stigma of the flower
Self pollination – transfer within the same
flower or between flowers of
the same plant
Cross pollination –transfer to a genetically
distinct flower
Double fertilization gives rise to the
zygote and endosperm
• ndosperm development usually
E
precedes embryo development.

15. Endosperm
 he endosperm is rich in nutrients, which it provides to
T
the developing embryo.
 n most monocots and some eudicots, the endosperm
I
also stores nutrients that can be used by the seedling
after germination.
 n many eudicots, the food reserves of the endosperm
I
are completely exported to the cotyledons before the
seed completes its development, and consequently the
mature seed lacks endosperm.

16. Embryo and suspensor
 he first mitotic division of the zygote is transverse, splitting the
T
fertilized egg into a basal cell, and a terminal cell which gives
rise to most of the embryo.
 he basal cell continues to divide transversely, producing a
T
thread of cells, the suspensor, which anchors the embryo to
its parent.

17. Embryo and suspensor
 he suspensor pushes the embryo into the endosperm
T
 he suspensor may develop into a large haustorium which
T
draws nutrients to the embryo from the parent
 he terminal cell divides several time and forms a spherical
T
proembryo attached to the suspensor.
 otyledons begin to form as bumps on the proembryo.
C
-A eudicot, with its two cotyledons, is
heart- shaped at this stage.
-Only one cotyledon develops in monocots.

18. The embryo
 After the cotyledons appear, the embryo elongates.
-Cradled between cotyledons is the apical meristem of the embryonic
shoot.
-At the opposite end of the embryo axis, is the apex of the embryonic root,
also with a meristem.
 After the seed germinates, the apical meristems at the tips of the shoot and
root will sustain growth as long as the plant lives.
-The three primary meristems - protoderm, ground meristem, and
procambrium - are also present in the embryo.
 During the last stages of maturation, a seed dehydrates until its water
content is only about
5-15% of its weight.
- The embryo stops growing until the seed germinates.
- The embryo and its food supply are enclosed by a protective seed coat
formed by the integuments of the ovule.

19. The Seed
 In the seed of a common bean, the embryo consists of an elongate
structure, the embryonic axis, attached to fleshy cotyledons.
- Below the point at which the fleshy cotyledons are attached, the
embryonic axis is called the hypocotyl and above it is the
epicotyl/ plumule, consisting of the shoot tip with a pair of
miniature leaves.
- The hypocotyl terminates in the radicle, or embryonic root.

20. The Seed
 While the cotyledons of the common bean supply food to the
developing embryo, the seeds of some dicots, such as castor beans,
retain their food supply in the endosperm and have cotyledons that
are very thin.
- The cotyledons will absorb nutrients from the endosperm and
transfer them to the embryo when the seed germinates.

21. The Seed
 The seed of a monocot has a single cotyledon.
- Members of the grass family, including maize and wheat, have a
specialized cotyledon, a scutellum.
- The scutellum is very thin, with a large surface area pressed
against the endosperm, from which the scutellum absorbs
nutrients during germination.
 The embryo of a grass seed is enclosed by two sheaths, a
coleorhiza, which covers the young root, and a coleoptile, which
cover the young shoot.

22. Types of seed
germination
1. ypogeal germination
H
2. pigeal germination
E

24. Life cycle of angiosperms