Gynoecium

The gynoecium is an important part of a flower. It is the innermost part and is made up of one or more pistils. These pistils produce ovules, which eventually develop into the fruit and seeds of the plant. The gynoecium is usually surrounded by the pollen-producing parts of the flower, called stamens.

We often call the gynoecium the "female" part of the flower. This is because it helps create the structures that will produce egg cells. However, it is important to remember that the flower itself is not male or female—it is the part that makes the egg cells that determines this role.

In plants like mosses, liverworts, and hornworts, the word gynoecium is also used to describe clusters of special structures called archegonia, along with any changed leaves or stems on the plant. These help in the production of female gametes.

The way the gynoecium develops and is arranged helps scientists identify and study different kinds of flowering plants, known as angiosperms. However, understanding the gynoecium can sometimes be tricky, making it a fascinating area of study in plant biology.

Introduction

Unlike most animals, plants can grow new parts even after they start growing. This includes roots, leaves, and flowers. In flowering plants, a special part called the gynoecium forms in the middle of the flower. It can be one piece called a carpel or several carpels stuck together.

After the plant’s seeds form, the gynoecium turns into a fruit. The fruit helps protect the seeds and often helps them spread to new places. The gynoecium has special tissues that come from different cells working together. These tissues help make the parts of the gynoecium, such as the pistil, carpels, ovary, and ovules. The carpel margin meristem helps make the ovules, parts of the ovary, and helps stick the carpels together.

animals plants embryogenesis meristems primordium ovules

Pistil

"Pistil" redirects here; not to be confused with Pistol.

The gynoecium, which is the innermost part of a flower, can have one or more pistils. A pistil usually has three main parts: an ovary at the base, a style in the middle, and a stigma at the top.

• The ovary is the swollen bottom part that holds tiny structures called ovules, which can grow into seeds.
• The style is a tube-like section that helps pollen reach the ovary.
• The stigma is the top part that catches pollen from other flowers.

Carpels

The parts of a flower that make seeds are called carpels. A carpel is the female part of a flower and usually has a style, a stigma, and an ovary. Inside the ovary are tiny structures called ovules, where the egg cells form. A group of carpels together makes up what we call a pistil. Carpels can be very small, like in some orchids, or very large, like in the plant Entada gigas.

Types

A gynoecium may have one carpel, called monocarpous, or many separate carpels, called apocarpous. When many carpels join together to form one structure, it is called syncarpous. Sometimes a syncarpous gynoecium can look very similar to a monocarpous one.

The way carpels join in a syncarpous gynoecium can differ. They might join only at the base, keeping separate styles and stigmas. Sometimes they join completely except for their stigmas. In some plants like Apocynaceae, carpels join at their styles or stigmas but have separate ovaries. When carpels join, their ovaries can be called a single compound ovary. It can be tricky to tell how many carpels joined together. If the styles and stigmas are separate, they can help count the carpels. Inside the compound ovary, the carpels might have separate sections divided by walls called septa. If there is only one style, stigma, and one section in the ovary, we might need to look at how the ovules are placed to learn more.

Pistil

Pistils start as tiny beginnings on a flower's growing tip, forming later and closer to the top of the flower than the sepals, petals, and stamens. Studies show that carpels, the parts of the pistil, are most likely similar to leaves.

A carpel works like a megasporophyll, but it usually includes a stigma and encloses ovules in its enlarged lower part, called the ovary.

In some early flowering plant groups, including Degeneriaceae and Winteraceae, a carpel starts as a shallow cup where ovules develop. The carpel then forms a folded, leaf-like shape that is not fully closed at the edges. It does not have a style, but has a wide stigmatic edge along the margin to allow pollen tubes to reach the surface.

Gynoecium position

In early flowering plants, the parts that make seeds are usually arranged in a spiral around a central base. In later plants, these parts tend to be in circles around the base.

Flowers can have different arrangements. Some flowers have a tube-like shape where the parts around the seed-making part are attached below it, called a superior ovary. Others have this tube shape up to the top of the seed-making part, called an inferior ovary. Examples include orchids, asters, and evening primroses. Between these, some flowers have a mix of both arrangements, called a half-inferior ovary, and are common in the rose family and saxifrages.

Sometimes, the seed-making part sits on a small stalk called a gynophore, as seen in Isomeris arborea.

Placentation

Main article: Ovule

Inside the ovary of a flower, small parts called ovules grow from special places called placentas. These placentas are often arranged in straight lines. In some flowers, there is one line of these places in each ovary. In others, the lines can be spaced along the wall of the ovary or near the center. When the ovary is divided into sections, the ovules grow from a line at the inner corner of each section. In a simple ovary without divisions, the ovules attach to a central column. Sometimes, a single ovule attaches to the bottom or top of a section of the ovary.

The ovule

Main article: Ovule

In flowering plants, an ovule is a special part inside the flower that helps make seeds. It starts as a small structure with a stalk and protective layers. Inside, one cell changes and creates a group of cells that includes an egg cell. When pollen from another flower reaches the ovule, it helps the egg grow into a new plant, starting the process of making seeds. The tiny opening in the ovule lets the pollen in, and the stalk keeps the ovule in place.

Role of the stigma and style

Main article: Stigma (botany)

The stigma is the special tip of a flower part that catches pollen when it lands there. It can look different in many plants — sometimes long and thin, sometimes round like a ball, and sometimes fuzzy. This helps it catch pollen from insects or other things that visit the flower.

The style is the tube-like part that connects the stigma to the rest of the flower. Together, they help make sure that pollen from one plant fertilizes another plant, not the same one, which helps plants grow stronger. Some plants, like Tasmannia and Degeneria, have Stigmas right along the edges of their flower parts without a style in between.