Difference Between Monocotyledon & Dicotyledon 🔬

Flowering plants, plants that produce flowers and seeds, can be sorted into two categories. It can either be a monocotyledon or dicotyledon; or monocot and dicot for short. I found this very interesting when I first learnt it in class because we usually do not look at growing plants in that way. What were also interesting were the differences at microscopic views. But before we do, let me explain a little on how to tell the difference by looking without the microscope.

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When you plant a seed, the first leaf/shoot that you see growing can either be one single leaf or two leaves. Didn’t know that? Me neither until my teacher explained it to us. All I just see is something come out of the ground and I go ‘Hey, cool something is growing’, and that’s it. Anyways, these first leaf/leaves that you see are called cotyledon/s. Thus giving their names mono (one) or di (two) – cotyledon.

Photo: Comparison of monocot and dicot sprouting by Peter Halasz. (User:Pengo), CC BY-SA 2.5

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Another difference we can see is also on the leaves, in particular the vascular structure type on the leaf. What is that? It is the veins you see on the leaf. Is it straight lines or branching lines? If it is straight, then it is a monocot. If it contains branching lines then it is a dicot.

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Another thing I just only discovered is the way the leaf grows. A dicot leaf grows from the tip or edge of the leaf. Whereas the monocot leaf grows from that base; this I already knew because of the oat grass I grow for Soju. I would pick off the strands for the impatient Soju to eat and wait for more to grow.

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Of course there are a few more features we could look at to determine the category. However I think it is time to look at the differences at a microscopic level. In particular the stem and root cross-section views.

Below is a diagram and information of what we will expect to see.

(drawn by yours truly)

Monocotyledon	Dicotyledon
Stem: Vascular bundle scattered throughout	Stem: Vascular bundle located at periphery of stem
Root: Vascular bundle arranged in circle towards middle of root	Root: Vascular bundle located in centre, xylem forms a star or cross shape. Phloem found around cross.

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Touching quickly on what a vascular bundle is, it comprises of cells that form tubes/ducts that allows the transport of water and nutrients. Think of it as a tunnel called Xylem which allows only water to travel via to distribute water throughout the plant. Or another tunnel called Phloem which allows only nutrients to travel via. These tunnels like to travel next to each other.

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Here is a fun fact:

Ever wondered what the rings you see on a tree when you cut it down? They are old xylem tissue/cells. Xylem only survives for a year before new ones are made; thus the reason why we see a ring a year which also allows us to count how old a tree is.

Picture Source by Luigi Chiesa, CC BY 3.0

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Here are pictures of the slide samples I have, excluding the dicot root. That picture is an old picture I had taken back in school. Unfortunately I do not have a slide of a dicot root of my own. 😢

Doesn’t the vascular bundle found in the monocot stem look like skull heads? Also a little hard to see the dicot one but it looks a little like a burger with jelly fish legs.

Here are my old drawings and parts labelled.

Looking at them, we can see the xylem is always bigger than the phloem and they are always next to each other.

Saving the best for last, I saw I had a ‘Woody Dicot Stem’ cross section slide so I thought I would check it out. I was blown away; I thought I was looking at a Mandela art! Check out the different patterns.

Unless cited, all other images/gifs belong to @supersoju

Unless linked, other information were taken from my class notes