1. The document discusses different types of endosperm, embryos, and cotyledons in plants. 2. There are three main types of endosperm based on development - nuclear, cellular, and helobial. Nuclear endosperm involves free nuclear divisions while cellular involves immediate cell wall formation. 3. Embryos can be dicot-style with two cotyledons and a radicle or monocot-style with a single scutellum cotyledon. Cotyledons are the first leaves that emerge from a germinating seed and store nutrients.

1. DIFFERENT TYPES OF
ENDOSPERM, EMBRYOS AND
COTYLEDONS
Raju Ram Choudhary
2019A48D

2. What is Endosperm?
Nutritive tissue for the developing embroys in angiosperms
Functionally it is comparable to female gametophyte in gymnosperms but has
unique origin.
Gametophyte – Haploid and before pollination
Endosperm – Triploid and product of fertilization

3. Types of endosperm (Depending upon mode of development)
Nuclear
Cellular
Helobial
 Cellular endosperm is largely restricted to dicotyledonous
families, in monocots it occurs only in Araceae and
Lemnaceae.

4. 1. Nuclear Endosperm
 Division of PEN and a few subsequent nuclear divisions are not
accompanied by wall formation
 Central cell of embryo sac has formed a few to several thousand
nuclei freely suspended in its sap.
 Ex: Floerkea, Limnanthes, Oxyspora.

5.  Degree of cellularization :
 Cellularization only around the embryo. Ex; Phaseolus
 Wall region confined to only micropilar end while chalazal region remains free
nuclear and it often elongates and behaves like an haustorium. Ex; Crotalaria
 Vermiform appendage at chalaza end. Ex; Grevillea robusta
 Beside the main chalazal haustorium, numerous single-celled finger-shaped
projections are present all over the endosperm. Ex; Lomatia polymorpha
 Coconut endosperm
 PEN undergoes a number of free nuclear divisons
 When fruit is about 50mm long the embryo sac filled with a clear fluid in which
float numerous nuclei of various sizes
 Gradually these free nuclei starts forming cells and setting at periphery of cavity,
and layers of cellular endosperm start appearing
 In mature coconuts the liquid endosperm becomes milky and it does not contains
free nuclei or cells

6. 2. Cellular endosperm
• Absence of free nuclear stage
• The division of the PEN and a few subsequent nuclear divisions are followed
regularly by wall formation.
• The occurrence of haustoria is a common feature of this type of endosperm; it
is more varied than that is the nuclear endosperm
• The first division of the PEN is followed by a transverse wall resulting into
two chambers of almost equal size.

7.  A very aggressive chalazal haustorium is formed in Iodina
rhombifolia. The haustorium is actually formed before
fertilization. After fertilization, the division of the primary
endosperm nucleus is followed by transverse partitioning of
the central cell, resulting in the formation of a micropylar
chamber and a chalazal chamber. The endosperm proper is
derived from the micropylar chamber alone. The chalazal
chamber functions as an aggressive, uninucleate haustorium.
Profuse branching at the free- end gives the haustorium a
coralloid appearance.
 In the Acanthaceae, the endosperm development is
asymmetric and it shows characteristic micropylar and
chalazal haustoria.

8. A very aggressive
chalazal haustorium
is formed in
Iodina rhombifolia.

9. 3. Helobial endosperm
 Intermediate above two type e.g., members of order helobiales Monocot
 First division is cellular (i.e., wall formation follows the first division)
 However, inside each of these newly formed cells, free nuclear divisions occur.
 But finally, the endosperm becomes cellular following the pattern of development
of nuclear endosperms.

10.  The primary endosperm nucleus moves to
the chalazal end of the embryo sac where
it divides forming a large micropylar
chamber and a small chalazal chamber.
 In the micropylar chamber, free- nuclear
divisions and cell formation, start at a
much later stage.
 In the chalazal chamber, the nucleus
either remains undivided or divides
only a few times.
 If latter is the situation, the divisions
are usually free- nuclear. Sometimes, in
Phylidrum lanuginosum, it may become
cellular.
 Example : Asphodelus tenuifolius

11. Embryo
Embryogenesis is a process that occurs after the fertilization of
an ovule to produce a fully developed plant embryo
The zygote produced after fertilization must undergo various
cellular divisions and differentiations to become a mature
embryo
An end stage embryo has five major components including the
shoot apical meristem, hypocotyl, root meristem, root cap, and
cotyledons
Plant embryogenesis results in an immature form of the plant,
lacking most structures like leaves, stems, and reproductive
structures.

12.  Six moments in embryogenesis
I. Two cell stage
II. Eight cell stage
III. Globular stage
IV. Heart stage
V. Torpedo stage
VI. Maturation
1. endosperm
2. single celled zygote
3. embryo
4. suspensor
5. cotyledons
6. shoot apical meristem (SAM)
7. root apical meristem (RAM)

13. Dicot Embryo
Basal cell forms a 6-10 celled suspensor
Terminal cell produces embryo except the radicle.
The first division of terminal cell is generally
longitudinal.
It consists of an embryonal axis and two cotyledons.
Plumule is terminal and lies in between the two
elongated cotyledons

14. Monocot Embryo
 Basal cell produces a single celled suspensor.
 The embryo is small and situated in a groove at one end of the
endosperm.
 There is a single cotyledon (Scutellum)
 Plumule appears lateral due to excessive growth of the single
cotyledon.
 The plumule and radicle are enclosed in sheaths. They are
coleoptile and coleorhiza.
 The outer covering of endosperm separates the embryo by a
proteinous layer called aleurone layer.

15. Schnarf (1929), Johansen (1945) and Maheshwari (1950) have recognized five
main types of embryos in dicotyledons.
The terminal cell of the two-celled pro-embryo divides by longitudinal wall.
1. Crucifer type:
 Basal cell plays little or no role in the development of the embryo.
2. Asterad type:
 Basal and terminal cells play an important role in the development of the
embryo
The terminal cell of the two-celled pro-embryo divides by a transverse wall, Basal
cell plays a little or no role in the development of the embryo.
3. Solanad type:
 Basal cell usually forms a suspensor of two or more cells.
4. Caryophyllod type
 Basal cell does divide further
5. Chenopodiad type:
 Both basal and terminal cells take part in the development of the embryo.

16. Cotyledons
“The embryonic leaf in seed-bearing plants, one or more of which are
the first to appear from a germinating seed.”
 Cotyledons are formed during embryogenesis, along with the root
and shoot meristems, and are therefore present in the seed prior to
germination.
 The cotyledon of grasses and many other monocotyledons is a highly
modified leaf composed of a scutellum and a coleoptile.
 The scutellum is a tissue within the seed that is specialized to absorb
stored food from the adjacent endosperm.
 The coleoptile is a protective cap that covers the plumule (precursor
to the stem and leaves of the plant)

17.  The number of cotyledons present is one characteristic used by
botanists to classify the flowering plants (angiosperms).
 Species with one cotyledon are called monocotyledonous
("monocots"). Plants with two embryonic leaves are termed
dicotyledonous ("dicots").
 Gymnosperm seedlings also have cotyledons, and these are often
variable in number (multicotyledonous), with from 2 to 24
cotyledons forming a whorl at the top of the hypocotyl (the
embryonic stem) surrounding the plumule.
 Within each species, there is often still some variation in cotyledon
numbers, e.g. Monterey pine (Pinus radiata) seedlings have 5–9,
and Jeffrey pine (Pinus jeffreyi) 7–13 (Mirov 1967)
 Other species are more fixed, with e.g. Mediterranean cypress
always having just two cotyledons. The highest number reported is
for big-cone pinyon (Pinus maximartinezii), with 24

18. Epigeal and Hypogeal
Epigeal - expanding on the germination of the seed, throwing off the seed
shell, rising above the ground, and perhaps becoming photosynthetic
Hypogeal - not expanding, remaining below ground and not becoming
photosynthetic