Monocots & Dicots

One-by-one or two-by-two, scientists use seed structure as a major classification tool.

Until recently, seeds were thought to exist in two basic forms: monocotyledons and dicotyledons. Since those words have so many syllables and are tricky to spell, most people call them monocots and dicots. Monocots, such as corn, have only one seed body. Dicots, such as beans and most nuts, easily break into two halves.

Monocots vs. dicots (PennState Wikispaces)

Way, way back, nearly a billion years ago, plants and animals diverged into two different life forms. Before that happened, life existed as eukaryotes. Eukaryotes are organisms with a true nucleus. They evolved approximately 2.7 billion years ago, but I digress.

What I find fascinating is that the complete protein originally found in eukaryotes is regained when we eat monocots and dicots at the same time. Crazy, right? Traditional meals of rice and beans, peanut butter and bread, even oatmeal cookies with nuts provide your body with the basic building blocks of life itself!

Traditional classification

Aside from having a single seed body, monocots also feature flower petals that are multiples of three, leaves with parallel veins, and fibrous roots. A cross section of the stem will show a chaotic arrangement of veins (vascular bundles). Bulbs, such as tulips and garlic, are modified monocots.

Dicots, on the other hand, have flower petals in multiples of four or five, leaf veins that are random or scattered, and vascular bundles that look like the rings of trees. They also have taproots. But dicots are no longer a classification. Well, not exactly.

Modern changes in taxonomy

Electron microscopes and genetic mapping have drastically changed the way we look at plants. Superficial similarities can no longer be used to classify them. In 1991, researchers learned that dicots were not as simple as we thought. In fact, dicots are not even included in the new taxonomy! This is because dicots are not all descended from a single ancestor. A new term was created to differentiate between simple, primitive dicots and more modern tricolpate dicots. [How’s that for a word?]. That new word is eudicot. 

Plant identification

So, how does understanding all this evolution help you in the garden? Plant classification can help you determine if you are looking at an infant prized heirloom tomato or a weed. Also, some herbicides are designed to only attack monocots, while others only kill dicots. Most important, cutting the top off of a monocot will kill it (lawns being a notable exception).

Can you identify the different classes of plants in your garden? I’ll bet you can!