The ovules is also known as megasporongia which are borne on a cushion-like tissue called placenta in the ovary. One or more than one ovules are present inside the ovary.

1. MEGASPORANGIUM
& TYPES OF OVULE

2.  Gynoecium is the female reproductive organ. The free
unit of gynoecium is called pistil or carpel.
 Carpel is also known as megasporophyll. In angiosperms
the carpel has a closed ovary bearing ovules on placentae.
The carpel is differentiated into three distinct region,
 Stigma - The free end of the carpel which receives pollen
grains.
 Style - A long, narrow tubular structure is present in
between the stigma and ovary.
 Ovary - The basal swollen part of the carpel.
• The ovules is also known as megasporongia which are
borne on a cushion-like tissue called placenta in the ovary.
One or more than one ovules are present inside the ovary.
INTRODUCTION
2

3. STRUCTURE OF MEGASPORANGIUM (OVULE)
 FUNICLE - Each ovule attached to the placenta by means of a thin stalk
called funiculus / Funiculum.
 Based on characteristics of structure of funicle, the ovules can be divided
into 3 types:
 The funicular (ovule with funiculus), the afunicular (funiculus as a
structure is absent) & sessile ones (funiculus is not morphologically
apparent and the ovule is attached to the placenta by means of the basal
part of the raphe).
 HILUM - The point of attachment of the funicle with the ovule. During
ripening, a separation layer is formed between the seed itself and the
funiculus (funicular seeds) or between the raphe and the placenta (sessile
seeds) and subsequently a remnant (scar) called hilum appears.
 RAPHE - In most of the ovule, funicle is attached to the main body of
ovule for some distance (at lateral side) to form a ridge like structure. It is
formed by union of funicle with the body of ovule.
3

4. • It is a glandular, non - vascular structure developing from funicle or placenta. Some filaments are attached
with funicle (some times placental).
• Obturators exhibit great variation in their origin, morphology, anatomy and extent of development.
• The function of obturators is to guide the passage of pollen tube towards the micropyle inside the ovary. The
pollen tube grows along the obturator.
 Funicular obturators are found in Magnoliaceae, Acanthaceae, Fabaceae,etc..
 Placental obturators are found occurs in Cucurbitaceae and Euphorbiaceae.
• In Crinum, the funiculus simply becomes knee-like and functions as an obturator.
• In Ceratocephalus, the cells of funicular epidermis, above the microphyle elongate radially with dense
cytoplasm acting as an obturator.
• In Thymelaeaceae the obturator originates from the stylar region. Cells of stylar canal elongate, extending up
to the microphyle.
• In Caltha the cells of the obturator show wall in growths, a characteristic feature of transfer cells.
• In Aegle some epidermal cells of funiculus as well as placenta elongate into densely cytoplasmic multicellular
hairs reaching as far as the micropyle.
4

5. An ovule develops as a papilla on the placenta. A hypodermal archesporial cell is differentiated.
 ARCHESPORIUM - It has a hypodermal origin. Cells which lay directly below the epidermis become
more conspicous, large in size and have prominent nucleus, they are called archesporial cell .
 The archesporial cell may divide periclinally to form outer primary parietal cell and inner primary
sporogenous cell. In some plants the archesporial cell directly behaves as megaspore mother cell.
 Primary parietal cell - Outer primary parietal cell forms the nucellus.
 Primary sporogenous cell - Inner primary sporogenous cell behave as megaspore mother cell.
 Nucellus is a diploid tissue that is present in the body of ovule, enclosed by integuments. It is a wall of
mega sporangium. The main region of the ovule is composed by mass of parenchymatous cells called
nucellus. Nucellus is the main part of ovule.
 Only one nucellus is present in each ovule, abnormally twin nucelli may occur in a common fold of
integuments. E.g. Aegle marmelos. Hydrocleys nymphoides.
5

6.  EPISTASE - There is similar group of specialized cutinized cells is found in the nucellar region, just
above the embryo sac. A well marked tissue in micropylar part of ovule.
 Usually originates from the apical cell of nucellar epidermis. It may be nutritive in function. E.g. Costus,
Castalia.
 PERISPERM - In most of the angiosperm, entire part of the nucellus is utilized by developing embryo sac
but in some of the angiosperm some part of the nucellus remain inside the ovules.
 That part of the nucellus present inside the seed in the form of a thin layer is known as perisperm. E.g.,
Commonly found in Piperaceae (Piper nigrum) and Zingiberaceae (Turmeric, Ginger).
 PSEUDO – EMBRYO SAC - The nucellus dissolves in the members of Podostemaceae family to form a
nutritional cavity.
 NUCELLAR BEAK - Nucellar tissue is generally confined to inner integument, but rarely it is projected
into micropyle (Caryophyllaceae) or beyond it forming a beak like structure called nucellar beak.
E.g. Members of Euphorbiaceae, Cucurbitacae, Nyctaginaceae.
6

7.  A place from where funicle and integuments arise is called chalaza. Four types of chalaza can be
distinguished:
 Pachychalaza or the massive one - Comprises most of the ovule or seed as compared to the nucellus and
integuments. E.g., Lauraceae.
 Perichalaza or the peripheral one - The unidirectional growth of the chalaza in the region of the raphe and
antiraphe occurs, resulting in replacement of the radial symmetry of the ovule and seed with the bilateral one.
E.g., Austrobaileyaceae.
 Mesochalaza or the intermediate one - The greater half of the formed ovule and the developing seed is
occupied by the nucellus and the integument or just by the integument. E.g., Araceae & Rhizophoraceae.
 Leptochalaza or the thin one - Represented by a small group of cells that become destroyed during seed
development. E.g., Fagales & Euphorbiaceae.
HYPOSTASE - Hypostase refers to a group of disc like or plate like cells present right below the embryo sac
and above the vascular supply to the funiculus.
• It is derived from nucellar cells. In some plants a group of thickened cells is found in the chalazal region just
below the embryo sac.
7
CHALAZA

8. • A well - defined but irregularly outlined group of nucellar cells with poorly cytoplasmic contents but have
partially lignified walls composed of a starch, proteins & lipids.
• Occasionally, the cells of the hypostase may surround a portion of the embryo sac and may even extend into
the micropylar half of the ovule.
• In the Loranthaceae, a hypostase is present below the archesporium. In Aristolochia, it persists in the
mature seed.
• Hypostase occurs in many families such as Amaryllidaceae, Liliaceae, Zingiberace, Euphorbiaceae,
Theaceae and Apiaceae.
• In Agave, the cells of hypostase accumulate starch, proteins and lipids.
FUNCTIONS:
• It maintains water balance in a resting seed during hot dry seasons.
• Take up protective role in mature seed.
• Hypostase forms a barrier or boundary for growing embryo sac and prevents from protruding into the base
of the ovule
• Hypostase transports nutrients by connecting the vascular bundle in the funiculus with the embryo sac
• It produces certain enzymes or hormones.
8

9. • The nucellus is covered by one or two coats called Integuments. Generally the ovule has one or two
integument . Most genera in monocot have two integument.
• FUNCTION - Integument forms seed coat in mature stage. Sometimes, it supplies nutrition.
• There are outer & inner integument. The integuments grow faster than the ovular body and form micropyle.
• In many plants it can be in different structure at young stages . In mature stage it can be absent or remain in a
complicated structure .
• In plants like Cananga, a middle integument is seen arising during megasporogenesis.
• There is a evidence that in some genera by a fusion of two separate primordia, a single integument has
originated.
• In Opuntia a peculiar condition occur where the extremely long funicles surrounds the ovule n looks like a
third integument . The 3rd integument can arise by splitting of outer integument, E.g., Ulmus .
• But most other cases it is a new structure arising from the base of the ovule, E.g., Asphodelus .
• In Euphorbiaceae, 3rd integument arise by a proliferation of the integumentary cells at the micropylar region,
called Caruncle.
• Some integument can possess chlorophyll, E.g., Morigna olifera , Gladiolus communis . Stomata can also
Stomata can also found in integument, E.g., Gossypium, Curvularia .
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INTEGUMENT

10. SOME SPECIAL INTEGUMENTS
 Aril : It is a sort of third integuments which develop from funicle or testa at the base
of the ovule.
E.g., Myristica, Asphodelus.
The aril may be develop as a true integument of false. The latter is formed by turning
of the tip of the outer integument. Such an aril is termed as arillode. E.g., Litchi.
 Operculum : It is a stopper or break like structure which is formed at the micropylar
end of the seed. It is formed due to the elongation of the cells of the inner integument.
E.g., Lemnaceae family (Lemna).
 Caruncle or Strophiole : It is formed due to the proliferation (out growth) of the cell
at the tip of the outer integuments over the micropyle. In a seed it over arches the
micropyle. It is formed by sugary contents so helps in absorption of water during
germination of seeds and dispersal of seeds by ants called myrmecochory.
E.g., Ricinus communis (Castor).
 Sarcotesta : When the outer integument become fleshy. It is called sarcotesta.
E.g., Magnoliaceae.
 Coma : Unicelled hair called coma arise from the epidermis of the outer integument.
Such seeds are described as comose.
E.g., In many plants like Calotropis, Gossypium.
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11. ENDOTHELIUM OR INTEGUMENTARY TAPETUM
 In most of the Tenuinucellate ovules, nucellar epidermis degenerates early and the innermost layer of the
integument becomes active to form a nucellus like tissue.
 Its cell possess a prominent nucleus. It is polyploid structure. Multinucleate condition present in Balanites.
Sometimes, binucleate condition. The cells are radially elongated dense cytoplasm and store starch and fats.
 It is single layered but it becomes multi – layered in some members of Asteraceae members. Helianthus has 10
– 12 layers. Having the similarities with the anther tapetum.
 It is a nutritive layer whose main function is to serve as an medium of transportation of food materials from
integument to embryo sac . In later stages, at the time of embryo’s maturity, the inner surface of
endothelium become cutinized and becomes a protective layer.
E.g., Helianthus and some plants of the Asteraceae family.
FUNCTIONS:
• Gives nutrition to embryo sac
• Works as a medium
• Gives protection
11

12.  Integument is absent just opposite to the chalaza, so that a narrow passage (pore) is formed which is
called micropyle. It may be formed either by the inner integument, in Centrospermales or by both inner
and outer integument , in Pontederiaceae where there is two integuments are present.
 When both integument take part in formation , a passage is formed by the outer integument, as a result
the micropylar canal has a zigzag outline. E.g., Melastomaceae .
 In Ficus, the integumentary cells come in contact with each other so that the canal of micropyle is
extremely narrow and imperceptible.
 In bitegmic ovules, it is generally formed by the inner integument, sometimes by both, rarely by outer.
When it is formed by both integuments, the micropylar canal encloses two tiny spaces.
o The space between outer and inner integuments, in the micropylar canal is called exostome.
o The space between inner integument and nucellus is called endostome.
 Function - The micropyle of ovule is usually meant for the entry of the pollen tube into the ovule.
12
MICROPYLE

13. TYPES OF OVULE
• The ovule can be formed in different size and shape . Many times it changes
its form during the course of its development.

14. ON THE BASIS OF INTEGUMENTS
 UNITEGMIC OVULE – They have a single
integument around ovule, termed as unitegmic ovule.
E.g., Members of Gamopetalae & Gymnosperm.
 BITEGMIC OVULE – They have two integument
around ovule, termed as bitegmic ovule.
E.g., In most of Angiosperm Polypetalae (Capsella) &
Monocots.
 ATEGMIC OVULE - The ovule in which integuments
are absent. They present in parasitic plants.
E.g., Olax, Liriosma, Loranthus & Santalum.
14

15. ON THE BASIS OF DIRECTION OF THE FUNICULUS
INFLEXION & POSITION OF OVARY
 EPITROPOUS OR ANTITROPOUS OVULES
In Epitropous one, the micropyle is turned in the opposite direction. The funiculus is curved from bottom to
top. The micropyle is directed upward to the upper end of the ovary. The ovule and carpel are flexing in
opposite directions. It divides into, - Epitropous dorsal (Abaxial, pointing away from central floral axis)
- Epitropous ventral (Adaxial, pointing towards the central floral axis)
 APOTROPOUS OR SYNTROPOUS OVULES
In Apotropous ovule the micropyle is turned towards the funiculus and placenta. The funiculus is curved
from the top downward. The micropyle is directed downward to the upper end of the ovary. The ovule is
flexing in the same direction as the carpel. It is also known as hypotropous ovules. It divides into,
- Hypotrpous dorsal (Abaxial, pointing away from central floral axis)
- Hypotropous ventral (Adaxial, pointing towards the central floral axis)
 PLEUROTROPOUS OVULES
In which the micropyle remains unturned and the funiculus does not curve. It divides into,
- Pleurotropous dorsal ( in which raphe is above) - Pleurotropous ventral (in which raphe is below)
15

16. ON THE BASIS OF NUCELLUS
 TENUINUCELLATE : The primary parietal cell is not differentiated and nucellus is not formed. The
parietal cell is absent and archesporial cell directly acts as a megaspore mother cell lies directly below the
nucellar epidermis.
 Sporogenous cell is hypodermal. The nucellus is either less developed or present in the form of single layer.
It is the most primitive type.
E.g., Gamopetalae group – Rubiaceae, Orchidaceae
 CRASSINUCELLATE : The primary parietal cell gives rise to nucellus. A well developed parietal tissue is
present and the microspore mother cell is separated from the nucellar epidermis by one or several layer .
 The nucellus may enlarge by an increasing number of parietal cell by few periclinal division and anticlinal
division. Sporogenous cell gets embedded in the massive nucellus.
E.g., Zizyphus. Several members in Salicaceae, Polygonaceae has a beak- shaped nucellus reaching out
the micropyle. Polypetalae group and Monocots.
16

17.  PSEDO – CRASSINUCELLATE : Sometimes, the nucellus is derived from the nucellar epidermis.
Because of the absence of parietal cells, the epidermis is divided and form many layer of cell.
E.g., Nigella damascena
17

18. TYPES OF OVULE
BASED ON THE POSITION OF MICROPYLE WITH RESPECT TO FUNICULUS

19. ORTHOTROPOUS OR ATROPOUS OVULE
 The body of ovule is upright in position.
 The micropyle, chalaza and hilum lie in one
straight line, so that this ovule is called
straight or upright ovule.
 It is the most primitive and most simple type
of ovule of angiosperms. Raphe is absent.
E.g., Betel, Piper, Polygonum, Urticaceae
and in Gymnosperms.
 These may be subdivided into additional
types based on the orientation of the
vasculature.
19

20.  ORTHO - AMPHITROPOUS TYPE
An ortho - amphitropous ovule is one in which the vasculature is straight, leading
from the funiculus base to the middle of the nucellus; the nucellus is bent sharply
in the middle along both the lower and upper sides, often with a “basal body”
present.
 ORTHO - CAMPYLOTROPOUS TYPE
An ortho - campylotropous ovule is similar to that of the ortho-amphitropous
type, except that the nucellar body is bent only along the lower side, with no “basal
body”. Characterized by persistence of the arc-shaped flexure of the ovule and
seed; embryos have different sizes and degrees of flexure; the structures of the
chalazal region remain in the initial ortho-position. Such a structure of ortho-
campylotropous ovules and seeds could be caused by changes in the structure of
the funiculus.
E.g., Capsella bursa-pastoris (Brassicaceae), seen in the members of
Euphorbiaceae & Potamogetonaceae
20

21. ANATROPOUS OVULE
 In this type, the body of the ovule is completely
turned at 180° angle, due to unilateral growth of
funiculus, so it is also called inverted ovule.
 The chalaza and micropyle lie in a straight line.
The hilum and micropyle lie side by side very close
to each other.
 This type of ovule is found in 80% families of
angiosperms but not in Capsella. In this ovule,
micropyle is facing downward condition.
 This is the most common type of ovule so that it is
considered as a "typical ovule" of angiosperms. .
It is also called resupinate ovule.
E.g., Castor & Members of Malvaceae,
Cucurbitaceae, Solanaceae, Asteraceae family.
21

22. These may be subdivided into additional types based on the orientation of
the vasculature.
 ANA - AMPHITROPOUS TYPE
An ana - amphitropous ovule is one in which a vascular strand curves,
traversing from the base of funiculus to the chalazal region of the nucellus;
the nucellus is bent sharply in the middle along both the lower and upper
sides, often with differentiated cells (called a “basal body”) at the angle of
the bend.
E.g., Alisma & seen in Asteraceae members.
 ANA - CAMPYLOTROPOUS TYPE
An ana - campylotropous ovule is similar to the ana - amphitropous type in
vasculature, differing in that the nucellus is bent only along the lower side,
with no “basal body”.
E.g., Capparidaceae & Cucurbitaceae.
22

23. HEMI - ANATROPOUS OR HEMITROPOUS OVULE
 In this ovule, the body of the ovule bents on funicle at 90°
angle, i.e., body of ovule is present at right angles to the
funiculus.
 This is an intermediate type between ortho and anatropous
ovules.
 This ovule is also called horizontal ovule because body of
ovule is present in horizontal position on the funiculus.
 Micropyle and chalaza are present in the same line but
micropyle is situated away from hilum.
E.g., Ranunculus, Primula, Golphimia.
 Based on the position of the structures of the ovule
chalazal region and on the shape of the axis of the
funiculus or raphe at their transition to the common
straight morphological axis,
23

24.  HEMI – ANATROPOUS TYPE
In which the axis in the ovule, when passing in a funiculus or a raphe, changes the angle of inclination
relatively to the placenta as a result of the displacement of the chalaza, the hypostase and the conducting
bundle into the hemi-position. This is a typical version of hemitropous ovule. E.g., Lilaea subulata
 HEMI - ORTHOTROPUS TYPE
The axis in the ovule curves through the funiculus or raphe toward the chalazal region retaining the ortho-
position. Due to the predominant growth of the micropyle and middle parts on the antiraphal side of the ovule
as compared to the raphal side in the great part of the integuments and nucellus, the morphological axis
running parallel to the placenta remains straight, therefore the micropyle does not approach the placenta.
E.g., Polygonum affine
 HEMI – CAMPYLOTROPOUS TYPE
In most representatives of this family, the ovules are anatropous, unitegmic and are characterized by the
formation of a complete raphe. The early developmental stages prior to the beginning of meiosis are similar,
but when the megasporogenesis is getting completed, the asymmetric chalaza is formed in Swertia iberica
ovules on the raphal side due to intensive cell division in the sub - epidermis, which coordinately causes
lengthening of the integument in the apical part, flexure of the micropyle and the embryo sac.
E.g., Swertia iberica (Gentianaceae)
24

25. CAMPYLOTROPOUS
OVULE
25
 In this ovule, the body of ovule curved
(Curvature is not effective) in such a way so that
micropyle and chalaza are not present in straight
line.
 The embryo sac and nucellus both are present in
curved position.
 Micropyle comes close to the hilum.
E.g., Fabaceae, Capparidaceae, Brassicaceae
family [Capsella]

26.  There is a viewpoint exists that amphitropous ovules differ from campylotropous ones
by the presence of a ‘basal body’.
 It should be noted that the ‘basal body’ can be of different morphological nature, and it
is described not only in amphitropous ovules, but in campylotropous ones as well.
 OB - CAMPYLOTROPOUS TYPE
Along with the true campylotropous ovule, the ob - campylotropous one can also be
distinguished, in which the antiraphe is the more developed part compared to the raphe.
26

27. AMPHITROPOUS OVULE
 In this type of ovule, curvature is more
pronounced or effective in the nucellus and due
to this effect of nucellus, embryo sac becomes
horse shoe shaped.
 Micropyle comes close to the hilum. It is also
called as transverse ovule.
E.g., Mirabilis, Lemna, Poppy, Alisma,
Butomaceae family.
27

28. These may be subdivided into additional types based on the orientation of the
vasculature.
 ANA - AMPHITROPOUS TYPE
An ana - amphitropous ovule is one in which a vascular strand curves,
traversing from the base of funiculus to the chalazal region of the nucellus;
the nucellus is bent sharply in the middle along both the lower and upper
sides, often with differentiated cells (called a “basal body”) at the angle of the
bend.
E.g., Alisma & seen in Asteraceae members.
ORTHO - AMPHITROPOUS TYPE
An ortho - amphitropous ovule is one in which the vasculature is straight,
leading from the funiculus base to the middle of the nucellus; the nucellus is
bent sharply in the middle along both the lower and upper sides, often with a
“basal body” present.
28

29. CIRCINOTROPOUS
OVULE
 In this type of ovule, body of ovule is inverted
once and again turned into straight position due to
the growth of funiculus so that body of ovule is
present at funicle at 360°.
 The entire body of ovule is surrounded by long
funicle.
 It is also known as coiled ovule. Micropyle is
situated away from hilum.
E.g., Plumbaginaceae, Cactaceae family -
Opuntia.
29

30. According to David (1966), 266 out of 315 families, for which the morphological type
of ovule is established, are dicotyledons. Differences at the level of the genus and even
of the species..
30
0
50
100
150
200
250

31. MEGASPOROGENESIS
 The process of formation of megaspore from megaspore mother cell
by meiotic division is known as megasporogenesis.
 During the development of ovule, in the beginning of this process,
nucellus develops from the placenta in the form of a small rounded
outgrowth like structure. At this stage, all the cells of nucellus are
undifferentiated and homologous and meristematic.
 This mass of cells is surrounded by single celled thick layer of
epidermis.
• A single hypodermal cell of nucellus is differentiated and increase
in size. It becomes different from the rest of the cells due to the
presence of distinct nucleus. It is called archesporial cell.
• Archesporium divides periclinally to form an outer primary
parietal cell and inner primary sporogenous cell. Activity of
primary parietal cell depends a type of plants.
31

32.  The primary sporogenous cell directly act as a megaspore mother cell. It is diploid & divides meiotically to
form four haploid megaspores.
• The four haploid megaspores generally arranged in linear tetrad. Generally, the lowermost or chalazal
megaspore remains functional.
• Out of tetrad of megaspores and the other three which lie towards the micropyle degenerate. This functional
megaspore produces female gametophyte. In most Angiosperms, chalazal megaspore remains functional.
• In Elytranthe , Balanophora the micropylar megaspore give rise to embryo sac and others are degenerate . A
similar condition occur in Onagraceae family . In Rosa sometimes 2nd micropylar megaspore functions .
32

33. MEGAGAMETOGENESIS
DEVELOPMENT OF FEMALE GAMETOPYTE (EMBRYO SAC)
 Megaspore is the first cell of the female gametophyte.
 The development of an embryo sac from a megaspore is
known as megagametogenesis. Embryo sac is 7 - celled.
 The nucleus of a functional megaspore divides mitotically
to produce four - four nuclei are formed at each poles (8
nuclei).
 Three of these nuclei comprise as egg apparatus which
move to one pole and produce a central egg cell and two
synergid cells situated on either side of the egg cell.
 Another three nuclei migrate to the opposite pole to give
rise to haploid & uninucleate antipodal cells, the two
nuclei remaining in the centre, the polar nuclei fuse to
form diploid secondary nucleus.
33

34. • The megaspore thus develops into a mature
megagametophyte or embryo sac.
Depending upon number of megaspore nuclei taking
part in formation of female gametophyte, three types of
developments are recognised as under,
 MONOSPORIC - When only one megaspore
nucleus is involved in formation of the female
gametophyte, the development is said to be
monosporic. E.g., Polygonum divaricatum
 BISPORIC - When two megaspore nuclei are
involved in formation of the female gametophyte, the
development is termed as bisporic. E.g., Allium
fistulosum
 TETRASPORIC - When all the four megaspore
nuclei take part in formation of the female
gametophyte, the development is called tetrasporic.
E.g., Peperomia
34

35.  https://www.brainkart.com/article/Types-of-Plant-Ovule_963/
 https://courses.lumenlearning.com/boundless-biology/chapter/plant-reproductive-development-and-structure/
 https://www.vedantu.com/biology/ovule#:~:text=Ans%3A%20There%20are%20categorically%20six,straight%2
0in%20the%20orthotropous%20ovule.
 https://www.biologydiscussion.com/angiosperms/angiosperms-with-diagram-plant-kingdom/52167
 http://www.bio.miami.edu/dana/226/226F09_4.html
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 https://byjus.com/questions/edible-part-in-the-fruit-of-litchi-is-1-mesocarp-2-aril-3-fleshy-thalamus-4-
cotyledons/
 https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/ovule
 https://www.cleariitmedical.com/2019/06/biology-notes-sexual-reproduction-in-flowering-plants.html
 https://academic.oup.com/aob/article/107/9/1465/168249
 https://www.zobodat.at/pdf/Wulfenia_25_0081-0109.pdf
 https://ccelms.ap.gov.in/adminassets/docs/25032021115405-605c79dd43fc5.pdf 35