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Dicotyledon

life science Maturity 11-13 Next article →

Dicotyledons, often called dicots, are a massive group of flowering plants. These plants belong to the larger category known as angiosperms. The name "dicotyledon" comes from a specific feature found in their seeds. A dicot seed contains two embryonic leaves called cotyledons.

These tiny leaves provide energy for the plant as it first begins to grow. There are approximately 200,000 different species within this vast group.

Young castor bean plant showing prominent cotyledons
Young castor bean plant showing prominent cotyledons

Understanding these plants is essential for studying how Earth's diverse ecosystems function.

Scientists distinguish dicots from monocotyledons, or monocots, through several physical traits. While monocots usually have one cotyledon, most dicots have two.

Peperomia caperata 1-OB9
Peperomia caperata 1-OB9

However, there are rare exceptions to this rule. For example, the plant Psittacanthus schiedeanus can have as many as twelve cotyledons. In terms of flower structure, monocots are typically trimerous, meaning their parts come in threes. Dicots are often tetramerous or pentamerous, meaning they have parts in fours or fives. You can also look at the leaf veins to tell them apart. Dicot leaves often show reticulate venation, which looks like a net. Monocot leaves usually have veins that run parallel to one another.

Internal structures also reveal the differences between these plant groups. In the stem of a dicot, the vascular bundles are arranged in concentric circles. In monocots, these same bundles are scattered throughout the stem. The roots of dicots develop from the radicle, which is the part of the embryo that becomes the root. Monocots often have adventitious roots instead. Furthermore, many dicots exhibit secondary growth, which allows the plant to grow thicker over time. This type of growth is generally absent in monocots. You can also find stomata, or tiny pores for breathing, on both sides of a dicot leaf. In monocots, these pores are more common on the lower side.

Modern science has changed how we classify these plants. For a long time, dicots and monocots were seen as two equal divisions of flowering plants. However, molecular phylogenetic research starting in the 1990s revealed a more complex story. This research uses DNA to trace how different species are related. Scientists discovered that dicots are not a monophyletic group. A monophyletic group includes a single ancestor and all its descendants. Instead, the traditional dicot group is paraphyletic. This means it includes a common ancestor but leaves out some of its descendants. Specifically, monocots actually evolved from within the traditional dicot group.

Because of this discovery, the eudicots were identified as a major group. Eudicots are the largest monophyletic group found within the dicotyledons. They are separated from other flowering plants by the specific structure of their pollen. Most other flowering plants have monosulcate pollen, which has a single sulcus, or furrow.

Amborella trichopoda
Amborella trichopoda

In contrast, eudicots possess tricolpate pollen. This means their pollen grains have three or more pores set within furrows called colpi. This microscopic difference helps botanists organize the tree of life with much higher precision.

Botanists use different systems to name and organize these plant families. The APG IV system is the current consensus used by many scientists. This system recognizes that the traditional dicot group is paraphyletic to the monocots. Older methods, such as the Cronquist system, used different names. In the Cronquist system, dicots were often treated as a class called Magnoliopsida. This name was based on the type genus Magnolia. Other systems, like the Dahlgren and Thorne systems, used different ways to categorize the various orders of plants. These historical shifts show how much our understanding of biology evolves with new technology.

Today, studying dicots connects us to many different scientific fields. It links botany to genetics through the study of DNA and evolution. It also connects to ecology by showing how 200,000 species interact with their environments.

Victoria Regia01
Victoria Regia01

From the giant water lilies to the smallest garden flowers, these plants shape our world. Whether looking at the net-like veins of a leaf or the pollen under a microscope, the details of dicots reveal the deep history of life on Earth.

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🖼️ Images & Media (10)
File:Dicotyledon plant-let.jpg
Dicotyledon plant-let.jpg
File:Young castor bean plant showing prominent cotyledons.jpg
Young castor bean plant showing prominent...
File:Amborella trichopoda.jpg
Amborella trichopoda.jpg
File:Victoria Regia01.jpg
Victoria Regia01.jpg
File:Kadsura japonica (fruits s6).jpg
Kadsura japonica (fruits s6).jpg
File:Ascarina lucida - Mike Dickison - 461357202.jpeg
Ascarina lucida - Mike Dickison - 461357202.jpeg
File:Peperomia caperata 1-OB9.jpg
Peperomia caperata 1-OB9.jpg
File:CeratophyllumSubmersum.jpg
CeratophyllumSubmersum.jpg
File:Darlingtonia californica ne1.JPG
Darlingtonia californica ne1.JPG
File:Dracaena reflexa.JPG
Dracaena reflexa.JPG
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