Monocot vs Dicot: Key Differences and Examples to Help You Remember

Introduction

All species of flowering plants can be classified as either monocots or dicots, which refers to the number of cotyledons the plant embryo contains. The cotyledon is the portion of the plant embryo that is leafy, stemming off of a shoot called the hypocotyl that connects other sections of the embryo. Plants that are monocots have one cotyledon, while dicots have two cotyledons in their embryos. Here are some key differences between the two types of flowering plants and how to distinguish them from one another.

Leaves

Monocots have leaves that are known as isobilateral, which means that both sides are made of the same tissue and appear the same to the naked eye. These leaves must be equally exposed to sunlight on all sides, so they are usually vertical in appearance, allowing the sun to shine on the entirety of the leaf throughout the day. Monocots with distinguishable isobilateral leaves include corn, lilies, and irises.

Dicot leaves, on the other hand, are dorsiventral, meaning that they have an upper and lower surface that differ in appearance and structure. There are often many more stomata cells on the lower surface of dorsiventral leaves, whereas isobilateral leaves have an even distribution of the cells. These leaves often also are attached to the dicot plant at a perpendicular angle, allowing sunlight to shine directly onto the upper surface of the leaf. Plants with dorsiventral leaves include most trees and wildflowers.

Another way to distinguish monocots and dicots based on their leaves is by looking at the vein structure within the leaves. Monocots have a parallel venation, meaning that the veins within the leaf run parallel to one another and do not become entangled or branch off each other. Plants like coconuts and wheat display strong examples of this parallel venation. Dicot plants, on the other hand, have reticulated venation. Leaves with this type of venation have veins that stem off of one another throughout the entire leaf, creating a web-like structure with veins of varying lengths and thicknesses. Papaya and hibiscus leaves have noticeable reticulate venation like many other dicots.

Roots

Another distinguishable feature between monocots and dicots is their differing root systems. Monocots are known for having a fibrous root system. The systems consist of many thin roots of varying lengths branching from the stem of the plant. There is no main or tap root, in the fibrous root system. Instead, many roots form a circular shape as they stretch away from the source. Plants like rice and bananas have observable fibrous root systems representative of most monocots. Dicots, on the other hand, have a taproot system. Unlike fibrous root systems, taproot systems consist of a large root branching downwards from the center of the plant with smaller roots stemming off of it. Taproot systems often plunge much deeper into the soil than fibrous root systems, allowing them to absorb nutrients. Plants with distinguishable taproots are dandelions, carrots, and beets.

Petal Grouping

The number of cotyledons in plant embryos affects many features of the adult plant, including the grouping of its petals. In dicots, petals are often seen in multiples of four or five. Primary examples of this grouping include flowers like magnolias and roses, as well as geraniums. In monocots, flower petals most readily appear in groupings of three. Flowers such as tulips, and daffodils are good examples of this. The petal grouping can also be observed in larger plants, such as palm trees.

Secondary Growth

Secondary growth refers to the increase in the thickness of certain plants. The cause is cell division in the more mature stages of a plant’s life. This growth results in wood or bark surrounding the plant in a protective layer. While monocots used to be able to participate in secondary growth, most species have lost the ability to do so. Certain monocots can still produce an outer layer, like palm and agave trees, as well as bamboo. Dicots, however, very commonly display secondary growth, as seen in various tree species.

Vascular Arrangement

The stem of every plant contains vascular tissue. This tissue aids in the transport of various nutrients and communication signals between different parts of the plant. This tissue occurs in bundles, and these bundles distribute differently in monocots and dicots. If you were to look at the inside stem of a monocot, the vascular bundles are distributed throughout the area of the stem from the periphery to the center. In dicots, these bundles are located solely at the periphery of the stem. Thus, offering another manner in which to distinguish the two types of plants.