Difference Between Anatropous and Orthotropous Ovule

The difference between anatropous and orthotropous ovules lies primarily in their orientation within the ovary. Anatropous ovules are characterized by a downward-pointing orientation, with the micropyle at the top. In contrast, orthotropous ovules are upright or straight, with the micropyle situated at the bottom. In this article, we will learn about the difference between Anatropous and Orthotropous Ovules along with their examples.

Difference Between Anatropous and Orthotropous Ovule

The difference between Anatropous and Orthotropous Ovules can be summarized as follows:

Characteristic	Anatropous Ovule	Orthotropous Ovule
Orientation	Inverted	Upright
Curvature	Undergoes a 180-degree curvature	Straight/no curvature
Micropyle position	Positioned at the bottom	Positioned at the apex/top
Funicle Attachment	Attached via the funicle at the micropyle end	Attached at the base of the ovule away from the micropyle
Common examples	Lily, Onion, Orchids	Most gymnosperms, roses
Occurrence	It occurs in 80% of all angiosperms.	Found in host gymnosperm families.
Advantage	Adaptations for specific pollination/fertilization	Versatile, adapted to various pollination methods like insect and wind pollination.

Meaning of Ovule in Plants

Ovules are the fundamental female reproductive structures of a plant. They are found within the ovary of flowering plants (angiosperms) that give rise to seeds upon fertilization. Ovules contain the female gametophyte, which produces the egg cells necessary for fertilization, as well as protective layers and tissues that support the development and maturation of seeds.

In angiosperms, ovules develop into seeds enclosed in fleshy fruit upon fertilization. In gymnosperms, like conifers and geckos, ovules are found within the cones of these plants and, upon fertilization, form naked seeds.

What is Anatropous Ovule?

Anatropous ovules are characterized by an inverted orientation within the ovary. These ovules have a 180-degree curvature of the ovule during development, leading to its inverted orientation. In this position, the ovule is attached to the ovary wall via a funicle structure, with the micropyle facing downwards.

Examples of Anatropous Ovules

Several plants have anatropous ovules, such as

• Apples
• Lillies
• Helianthus
• Beans
• Sunflowers

What is Orthotropous Ovule?

Orthotropous or atropous ovules exhibit a straight, upright orientation within the ovary. Unlike anatropous ovules, orthotropous ovules do not undergo curvature during development. Instead, they maintain a linear alignment, with the micropyle positioned at the apex or uppermost part of the ovule.

Example of Orthotropous Ovule

The plants that have orthotropous ovules are:

Gymnosperms like Pinus, Cycas, etc.

• Roses
• Piper nigrum
• Polygonum

Conclusion: Difference Between Anatropous and Orthotropous Ovule

Ovules are essential structures that are responsible for the production of seeds. All plants have ovules for successful reproduction and propagation. They are of various types based on their orientation in the ovary in flowering plants. Anatropous and Orthotropous ovules are thus two types of ovules with inverted and upright arrangements in the ovary, respectively. Both are essential for the fusion of pollen grains and the production of seeds and fruits.

FAQs on Anatropous and Orthotropous Ovule

Is Pinus Ovules Orthotropous or Anatropous?

The ovules of Pinus and most gymnosperms are Orthotropous, meaning they are upright with the micropyle facing the top of the ovary.

Is the Ovule of Cycas Orthotropous?

Yes, the ovules of Cycas are orthotropous as they are upright in orientation, and their micropyles face the apex.

What are Some Examples of Anatropous and Orthotropous Ovules?

Examples of anatropous ovules are beans, apples, lilies, etc., while orthotropous ovules are Pinus, Cycas, roses, etc.

What do you Mean by Orthotropous Ovules?

Orthotropous or atropous ovules are those that have an upright orientation with the ovary of a plant. They have the micropyle facing the top and have no curvature.

What is the Difference Between Anatropous and Orthotropous Ovules?

The difference between anatropous and orthotropous ovules is that anatropous ovules are present at 180-degree curvature in the ovary, with the micropyle facing downwards, while orthotropous ovules are upright.

What is Anatropous Ovule with Example?

An anatropous ovule is a type of ovule that is inverted or turned back upon itself, with the micropyle and chalaza close together. An example of a plant with anatropous ovules is the tomato (Solanum lycopersicum).