Back to: Botany 300 Level
Hello, my brilliant friend! I hope you’re doing great today! Have you ever peeled the stem of a plant and noticed different layers inside? Or wondered why some plants, like maize, have soft stems while others, like mango trees, grow thick and woody? The secret lies in their internal structure! Today, we’ll explore the anatomy of stems in monocots and dicots and why they look and function differently.
Anatomy of stems in monocots and dicots
Understanding Monocot and Dicot Stems
Plants are classified as monocots (e.g., maize, palm, banana) or dicots (e.g., mango, hibiscus, beans) based on their seed structure. This classification also affects the structure of their stems.
Monocot stems are usually herbaceous (soft and green).
Dicot stems can be herbaceous or woody, with thickening over time.
Let’s look at their internal structures (anatomy)!
Anatomy of a Dicot Stem
Dicot stems have a well-organised vascular system, allowing them to develop secondary growth (wood formation). The main layers, from outer to inner, are:
Epidermis – The outermost protective layer with a cuticle and sometimes trichomes (tiny hairs).
Cortex – A region made of parenchyma and collenchyma cells that store food and support the stem.
Endodermis – A thin layer separating the cortex from the vascular tissues.
Vascular Bundles (Xylem and Phloem) – Arranged in a ring around a central pith:
Xylem (transports water) is on the inner side.
Phloem (transports food) is on the outer side.
Cambium (a layer between xylem and phloem) helps in secondary growth (wood formation).
Pith – A central region made of parenchyma cells for storage.
This ring-like vascular arrangement allows dicot stems to grow thick and strong over time, forming woody structures in trees and shrubs.
Anatomy of a Monocot Stem
Monocot stems have a scattered vascular system and do not develop secondary growth. The main layers include:
Epidermis – A single outer protective layer with a cuticle.
Ground Tissue – Unlike dicots, monocots lack a distinct cortex and pith. Instead, they have a uniform ground tissue for storage and support.
Vascular Bundles – Scattered throughout the ground tissue:
Xylem (water transport) is inside the bundle.
Phloem (food transport) is outside the bundle.
No Cambium, meaning no secondary growth (no wood formation).
This scattered vascular system makes monocot stems flexible but unable to become thick and woody, which is why plants like maize and banana remain soft.
A Simple Story to Understand This Concept
Imagine two friends planting crops:
One plants mango (a dicot), which grows thick and strong over the years because of its cambium.
The other plants maize (a monocot), which grows fast but stays soft and flexible because it lacks cambium.
This is why trees like mango last for decades, while maize plants die after one season!
Summary
Dicot stems have vascular bundles in a ring, allowing secondary growth (wood formation).
Monocot stems have scattered vascular bundles, so they do not grow thick and woody.
Dicots have distinct cortex and pith, while monocots have ground tissue.
Monocot plants remain soft, while dicots can become trees and shrubs.
Evaluation
- How are vascular bundles arranged in dicot stems?
- Why do monocots lack secondary growth?
- What is the function of the cambium?
- How does the pith differ in monocots and dicots?
- Why do monocot plants remain herbaceous while dicots can become woody?
You are doing an amazing job! Now, the next time you see a tree or a maize plant, you’ll understand why their stems look different! Keep learning with Afrilearn, and I’ll see you in the next exciting lesson. Stay curious and keep growing!
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