Question

explain the types of the ovules

Answer 1

Types of ovule

There are six types of ovules:

1. Orthotropous or atropous ovule

(ortho-straight, tropous - turn)

The body of the ovule is erect or straight. The hilum, chalaza and the micropyle lie in a straight line e.g.Polygonum.

2. Anatropous ovule

(ana - backward or up, tropous - turn)

The body of the ovule becomes completely inverted during the development so that the micropyle lies very close to the hilum (eg) Gamopetalae members.

3. Hemi-anatropous or hemitropous ovule

The body of the ovule is placed transversely at right angles to the funicle. The micropyle and chalaza lie in one straight line e.g.Ranunculus.

4. Campylotropous ovule

(kampylos - curved)

The body of the ovule is curved or bent round so that the micropyle and chalaza do not lie in the same straight line. e.g. Leguminosae.

5. Amphitropous ovule

The curvature of the ovule is very much pronounced and the embryosac also becomes curved e.g.Allismaceae, and Butomaceae.

6. Circinotropous ovule

The nucellus and the axis are in the same line in the beginning but due to rapid growth on one side, the ovule becomes anatropous. The curvature continues further and the micropyle again points upwards (e.g.) Opuntia.

Answer 2

Types of Ovules

Ovules have been separated into six categories based on their shapes:

Orthotropous (Atropous)

This is where the body of these ovules is straight so that the chalaza, where the nucellus and integuments merge, the funicle, which attaches the ovule to the placenta, and the micropyle are all aligned.

Anatropous

In this case, the ovules become completely inverted during development so that the micropyle lies close to the hilum. The hilum is a scar that marks the point where the seed was attached to the fruit wall by the funicle.

Hemi-anatropous

The body of these ovules becomes at a right angle in relation to the funicle, so it looks like the ovule is lying on its side.

Campylotropous

The body of this type is bent and the alignment between the chalaza and micropyle is lost. The embryo sac is only slightly curved.


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Amphitropous

The body of the ovule is very much curved that the embryo sac and the ovule itself take the shape of a horseshoe.

Circinotropous

The funicle in this case is especially long that it creates a nearly full circle around the ovule whose micropyle is ultimately pointing upwards.