What Is a Carpel? The Seed Bearing Unit of a Flower
A carpel is the basic seed bearing unit of a flower. The Master Gardeners of Northern Virginia define it as a structure that contains an ovary with one or more ovules, a stigma and often a style. The word comes from the Greek karpos, meaning fruit.
The short answer
Each carpel is one unit of a flower’s female part. It holds an ovary with ovules, a stigma and often a style. A single carpel forms a simple pistil. Several fused carpels form one compound pistil, and the number of chambers in the ovary can reveal how many carpels fused.
What is a carpel?
NC State calls the pistil the female structure of a flower, and the Northern Virginia glossary calls a pistil a carpel or a group of fused carpels. Colorado State says fruit consists of carpels where the ovules develop, plus the ovary wall or pericarp. See what forms inside in cannabis seed anatomy.
How do carpels form a pistil?
The Northern Virginia glossary covers three cases. One carpel makes one simple pistil. Two or more separate carpels make an equal number of simple pistils. Fused carpels make one compound pistil. All the carpels of a flower together are called the gynoecium.
| Carpels | Pistil | Source |
|---|---|---|
| One | One simple pistil | Northern Virginia |
| Several, separate | Several simple pistils | Northern Virginia |
| Several, fused | One compound pistil | Northern Virginia |
How can you count carpels in fruit?
Slice the fruit across its middle. The Northern Virginia glossary says the number of styles, stigma lobes or locules, which are chambers in the ovary, can reveal the number of carpels. The University of Minnesota says a simple fruit forms from one carpel or from fused carpels that look like one.
How to: step by step
- Slice a tomato or pepper across the middle.
- Count the seed chambers.
- Look at an open flower of the same plant.
- Count the stigma lobes.
- Compare the two counts.
Troubleshooting
Chambers hard to see: use a firm, unripe fruit.
Flower has no pistil: NC State says some flowers have no pistil.
Curious about leaves: read cannabis leaf anatomy and how bees move pollen in what roles do bees play in outdoor cannabis.
Carpels make fruit
Each fruit traces back to its carpels. See how seed types differ in six differences between feminized and autoflowering weed seeds. Kind Seed Co shares more plant science notes for curious growers.
Sources
- Gynoecium, carpel, pistil, Master Gardeners of Northern Virginia
- Extension Gardener Handbook, chapter 3: botany, NC State Extension
- Botany (CMG GardenNotes 120), Colorado State University Extension
- Chapter 8: terms, The Science of Plants, University of Minnesota Libraries
- Chapter 3: basic botany, plant physiology, and plant classification, University of Tennessee Master Gardener Program
FAQ
Is a carpel the same as a pistil?
Not always. The Northern Virginia glossary says the words are often used interchangeably but a pistil can be one carpel or several fused carpels.
Is an apple core the ovary?
Yes. The University of Minnesota says apple flesh is hypanthium tissue and the ovary is the papery core that encloses the seed.
What are fused carpels?
Carpels joined into one compound pistil. The Northern Virginia glossary calls this gynoecium syncarpous.
Do all flowers have carpels?
No. NC State says some plants have flowers with no pistil, such as male only staminate flowers.
What does carpel mean?
The Northern Virginia glossary says the word comes from the Greek karpos, which translates to fruit.
