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Monocot: Definition, Function & Examples

Instructor: Adrienne Brundage

Monocots are one of the two major types of flowering plants, and are characterized by having a single cotyledon, or seed leaf. Grains, grasses, bamboo and onions are all examples of monocots.

We also recommend watching Classification of Vascular, Nonvascular, Monocot & Dicot Plants and Structure of Plant Stems: Vascular and Ground Tissue

Definition

Ah, plants. These organisms make up a good portion of the living things on earth, and do all manner of important jobs for us. They provide us with food and energy, take carbon dioxide out of the air, recycle nutrients, and sometimes just look pretty.

There are so many plants on earth that scientists have taken to categorizing them, just so it's a little bit easier to study them. The first big category of plants has to do with if they have flowers or not. We then break up the flowering plants into two major groups based on their physical form and how many leaves are developed when the seeds first germinate.

If a plant has one seed leaf, or cotyledon, it falls into the group monocotyledon, or monocot for short. If a plant has two seed leaves, it falls into the group dicotyledon, or dicot for short. Since cotyledons are only present for a short period of time, it's usually much easier to recognize monocots due to their trimerous flowers (flower parts in multiples of three), and leaves with parallel veins.

What is a Cotyledon?

Since it's fundamental to the definition, let's talk a little bit about the cotyledon. A cotyledon is the first leaf developed by the embryo of a seed plant. These are those first little leaves that you see on the tender plant shoots of spring.

Monocots have one cotyledon, while dicots have two.
Monocots have one cotyledon, while dicots have two

Notice the picture on the left - it looks a little bit like new grass in the spring, doesn't it? While the picture on the right looks like a new flower seed that you planted in your garden. The shoot on the left is the cotyledon of the monocot. I bet you know what type of plant your grass is now, right? Yep, it's a monocot.

The Look of a Monocot

But let's be honest - how often are you crouched on the ground waiting for a seed to emerge? Probably not very often. So how is it possible to tell a monocot from a dicot when looking at mature plants? Luckily, the number of cotyledons is not the only physical feature of plants.

Monocots have a trimerous flower, or a flower with parts in multiples of three. You can simply count the petals of a flower, and if you can divide the total number by three, you probably have a monocot.

Lily flower with six petals
Lily flower with six petals

Look at the above image of a lily. Notice that there are six petals in total, a multiple of three. Lilies are a type of monocot. In fact, many of those big, showy flowers are monocots, like lilies, daffodils, bluebells, irises, orchids, and tulips.

But flowers are not the only way to recognize a monocot. The structure of the leaves is also a great clue. The veins in monocots are not arranged in circles, like in a tree. Instead, they are scattered throughout the plant. You can see the veins the best on the leaves of the plant, where they are arranged in parallel lines.

Iris leaf showing parallel veins
Iris leaf showing parallel veins

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