Question

Describe types of ovules diagrammatically.

Answer 1

In Angiosperms, six different types of ovules can be formed. These are:
1. Orthotropous
2. Anatropous
3. Campylotropous
4. Amphitropous
5. Hemianatropous
6. Circinotropous
1. Orthotropous ovule: 'The micropyle, chalaza and funicle lie in one straight line.
Example: family Polygonaceae, Piperaceae and ovule of most gymnosperms.
2. Anatropous (Inverted) ovule: The body of the ovule is completely inverted so that micropyle and hilum come to lie very close to each other. 82% of families of angiosperms contain this type of ovule.
Example: plants belonging to gamopetalae sub-class according to Bentham and Hooker classification.
3. Campylotropous: When the ovule is curved, the micropyle is directed towards chalaza. Chalaza is situated at right angles to funicle.
Example: Members of Cruciferae and Leguminosae family.
4. Amphibious or Transverse Ovule: The ovule curvature is more pronounced and embryo sac becomes horse-shoe shaped.
Example: Families Alismataceae, Butomaceae.
5. Hemianatropous Ovule: When nucellus and integuments lie more or less at right angles to the funicle.
Example: Families Ranunculaceae and Primulaceae.
6. Circinotropous ovule: The funicle is exceptionally long and forms a complete circle around the ovules, which is free from it except for a small area at the end of funicle.
Example: Opuntia and other members of families Cactaceae and Plumbaginaceae.