Structure of ovule

1. Structure of Ovule & Types of ovule
Dr. Vasanta I. Kahalkar
Assistant Professor
Department of Botany
M. G. Arts, Science & Late N. P. Commerce College
Armori

2. Ovule is the fertile part of Pistil. Morphologically
it is called megasporangium. The ovule consists
of the stalk and the body. It is protective outer
coat are called integuments and the stalk called
funicle. The ovule may have either one or two
integuments. Ovule with one integuments are
called unitegmic ovules and those have with two
integument are bitegmic.
The integuments envelops the inner nucellus
except at one place which is the opening known
as micropyle. This micropyle is the main passage
area for the entry of pollen tube. Nucellus is the
fertile part that form the female gametophyte
(embryo sac). Basal region of the ovule is called
chalaza.
Structure of ovule

3. • Following are the conditions seen in ovule in relation to
integuments :
(i) Unitegmic : Ovule with a single integument, e.g.,
sympetalous or gamopetalous dicotyledons.
(ii) Bitegmic : Ovule with two integuments as in polypetalous
(Archichlamydeae) dicotyledons and monocotyledons.
(iii) Caruncle : It is formed as an outgrowth of the outer
integument in the micropylar region.
Caruncle is common in the ovules of Euphorbiaceae. e.g.,
Castor (Ricinus).
(iv) Aril : In Asphodelus, a 3rd integuments called aril. Arises
from the base of ovule & its covers complete the other two
integument.
(v) Ategmic : In some parasites like Loranthus, Viscum,
Santalum etc., there is no integument. Such an ovule is
called ategmic.

4. Types of Ovules
• Based on the position of micropyle and chalaza
with respect to funicle, the ovule are of
following six types.
• a) Orthotropous
• b) Anatropous
• c) Hemi-anatropous
• d) Campylotropous
• e) Amphitropous
• f) Circinotropous

5. 1. Orthotropous
• The micropyle, chalaza and funicle are in
straight line. This is most primitive type of
ovules. e.g., Betel, Piper, Polygonum.

6. 2. Anatropous
• The body of the ovule is completely inverted
(turn at 180o angle ) so that micropyle and
funicle come to lie very close to each other.
e.g., 82% of angiosperm families.

7. 3. Hemi-anatropous
• Ovule turns at 90 angle upon the funicle or
body of ovule is at right angle to the funicle
e.g., Ranunculus.

8. 4. Campylotropous
• Ovule is circled more or less at right angle to
funicle. Micropylar end is bent down slightly.
e.g., in members of Leguminosae and
Cruciferae.

9. 5. Amphitropous
• The body of the ovule is very much curved and
embryo sac becomes curved like horse shoe
e.g. Lemna, Poppy,

10. 6 Circinotropous
• The funicle in this case is especially long that
it creates a nearly full circle around the ovule
and micropyle is ultimately pointing upwards.

11. Circinotropous
Campylotropous
Orthotropous Hemi-anatropous
Anatropous

12. THANK YOU