Pistil and Megasporangium: Definition, Structure, Types

Edited By Irshad Anwar | Updated on Aug 28, 2024 11:49 AM IST

Definition Of Pistil And Megasporangium

The female reproductive organ in the flower is the pistil. It comprises stigma, style, and ovary, inside which is located the megasporangium or ovule. Plant reproduction depends on it. Meiosis in it gives rise to megaspores that develop into the female gametophyte or embryo sac. It is involved in fertilisation and leads to the formation of seeds and eventually propagation of species of plant. As such, it plays a very vital role in the flowering plants' reproductive cycle. The pistil and megasporangium detail how plants reproduce themselves to hold populations.

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Structure Of The Pistil

The pistil refers to the female reproductive organ of a flower that produces ova or ovules, which after fertilisation, develop into seeds.

Components Of The Pistil

The pistil consists of three major parts: stigma, style, and ovary. The stigma is the sticky surface catching the pollen. The style connects it to the ovary, while the latter carries the ovules that develop into seeds upon fertilisation.

The Function Of Each Part

Stigma picks up pollen grains, the style gives way to pollen tubes that find their way down to the ovary, and the ovary contains the ovules which become seeds upon fertilisation.

Types Of Pistils

The types of pistils are described below-

Simple Pistil

A pistil containing a single carpel or a single unit of fused carpels; is usually found in flowers with a single ovary.

Compound Pistil

If two or more carpels unite, a compound pistil forms with an ovary that contains more than one chamber. This corresponds to the fact that there may be more than one loculus or compartment for ovules.

Differences Between Simple And Compound Pistils

The simple pistil has one chamber for ovules while the compound pistil has more than one chamber, each of which may have ovules. The compound pistil is bigger and more complex in structure.

Megasporangium (Ovule)

The megasporangium is that structure within the ovary where the megaspores develop into female gametophytes. But it is simply known as the ovule.

Structure And Location Within The Ovary

An ovule consists of a few parts like the nucellus, integuments, and the micropyle. The stalk by which the ovule is attached to the wall of the ovary is known as the funiculus.

Types Of Ovules Based On Position

Ovules can also be classified based on the orientation of these structures to the ovary. There are anatropous, orthotropous, and others; all differently varied from one another.

Frequently Asked Questions (FAQs)

1. What are the parts of a pistil and their functions?

A whole pistil is comprised of three major parts: stigma, style, and ovary. The stigma is the topmost part that captures pollen grains. The style is the stalk that connects the stigma to the ovary through which the pollen tubes grow to reach the ovary. The ovary contains the ovules; upon fertilisation, the ovules develop into seeds.

2. How does the megasporangium develop into an embryo sac?

Meiosis inside a megasporangium—a type of ovule—results in four megaspores. One megaspore will undergo mitotic divisions developing into the embryo sac, otherwise known as the female gametophyte. This includes the egg cell, which develops into an embryo upon fertilisation with sperm cells.

3. What is the difference between a simple pistil and a compound pistil?

A simple pistil is unilocular. While a compound pistil is formed by more than one but fused carpels, resulting in an ovary with multiple chambers, simple pistils likely have only one to the ovary; compound pistils may have as many as several ovules per ovary chamber.

4. What is the role of the pistil in pollination and fertilisation?

The most important part of a plant involved in the process of pollination and fertilisation is the pistil. This part holds and retains pollen grains. From here, because of the process of pollination, the pollen tubes grow and develop down through the style into the ovary, carrying with them the sperm cells. Inside the ovary, these sperm cells fertilise the ovules to finally produce seeds.

5. What are the common types of ovules based on their position?

The common types of ovules concerning their position are:

Anatropous ovule: Inverted ovule; the micropyle is directed towards the placenta.
Orthotropous ovule: Upright ovule; micropyle, chalaza and funiculus are in a straight line.
Campylotropous ovule: The Ovule is curved; the micropyle and chalaza are not in a straight line.
Amphitropous ovule: The ovule partially becomes inverted and curved with both ends of the ovule approaching each other.
Circinotropous ovule: It is an ovule that does a complete turn of 360 degrees.