The gynoecium

The "gynoecium" refers to all of the carpels in a flower. A carpel is a modified leaf of a flowering plant that has ovules on its edges. Carpels fuse singly or in groups to enclose their ovules.

A flower may have one to many carpels.

If a flower has multiple carpels, they may be separate, each carpel forming a separate pistil, or fused together, forming a single compound pistil.

Flower with many pistils
This flower has many carpels. Each carpel forms a separate pistil.

Flower with single pisitl
This flower has one pistil, but you cannot tell how many carpels are fused together to form it.

To determine the number of carpels in a pistil, you must recognize that carpels evolved from leaf-like structures with ovules on their edges.

cycad-like megasporophyll
The first seed plants were gymnosperms. Gymnosperms bear ovules on leaf-like structures, but do not enclose those ovules. You can see this type of structure in modern cycads.

Simple pistil
Leaf-like structures that fold and fuse to surround the ovules on their edges occur in angiosperms (flowering plants). This is a pistl formed from a single carpel (a single leaf-like structure with ovules on its edges.)

 

 

A cross-section of the ovary of a pistil will often reveal how many carpels make up a pistil. Look at where ovules are attached in the ovary and envision how leaf-like structures with ovules on their edges must be fused to form that ovary.

  • In the pistil above, only one carpel makes up the pistil: the carpel surrounds its ovules, and its fertile edges (where the ovules are attached) are fused together to form an internal space called a locule. Ovules are housed inside a locule.

Cross-sections of ovaries from three different pistils are shown below:

Cross-sections of three ovaries

 How many locules are in Ovary #1? (Click here)  

 How many locules are in Ovary 2? (Click here) 

 How many locules are in Ovary #3? (Click here) 

 How many CARPELS made up the pistil that had ovary #1? (Click here)  

 How many CARPELS made up the pistil that had ovary #2? (Click here)  

 How many CARPELS made up the pistil that had ovary #3? (Click here)           

 

Each pistil has a stigma, where pollen lands, a style, though which pollen tubes have to grow to reach eggs in the ovules, and an ovary.

Parts of a pistil