Everyone knows that carrots, onions, and potatoes are healthy to eat. But did you know that you’re actually eating the cortex of a plant? In this lesson, learn about the function of one part of a plant called the cortex.
Layers of a Plant Stem
If you were to describe a plant you would probably use words like simple, green, and leafy, right? But if you zoomed in, you’d see that a plant is comprised of many complex layers. Each layer has an important function and is essential to keeping the plant alive. Let’s briefly examine four layers found in the stem of a tomato plant.
Starting on the outside of the plant stem, this outermost layer is called the epidermis. The epidermis is like the skin of the plant. It helps protect the plant just like your skin protects you. Let’s shave off the epidermis and expose the next layer, called the cortex. Later in this lesson we’ll focus on this layer in detail.
But before we do this, let’s keep shaving off layers and dive deeper into the plant stem.The layer below the cortex is called vascular tissue. The vascular tissue is comprised of the xylem and phloem, which distribute water and nutrients throughout the plant.
The exact arrangement of the vascular tissues depends if it’s a dicot or a monocot plant. Remember, a monocot has a 1-seed leaf and a dicot has 2-seed leaves. We’re almost there; one last layer to explore.
The innermost layer, called pith cavity, stores water and starch. This last layer isn’t present in all plants, since monocots lack a pith.
Definition of the Cortex
Let’s explore the cortex layer in more detail.
The cortex is root and stem tissue found between the epidermis and vascular tissue of a plant. When you eat potatoes or carrots you are actually eating the root of a plant’s cortex. So, the next time you are at dinner, instead of saying, ‘please pass the potatoes,’ you should impress your family and say, ‘please pass the cortex.’
Function of the Cortex
The cortex can have numerous functions in plants, including food storage, mechanical support and photosynthesis. The exact function depends on the type of cells present. The cortex is comprised mostly of parenchyma cells, but can also contain sclerenchyma, or collenchyma cells.
Parenchyma cells have thin cell walls that can have multiple functions. If they are exposed to light, the cells can support photosynthesis, or if they’re located in plant roots the cells can store food. When parenchyma cells store food, it’s like how fat in our bodies help store extra energy. If the cortex has collenchyma cells present, the cells help support new plant growth.
Lastly, if the cortex has sclerenchyma cells present, the cells provide structural support to the plant stem keeping it upright. Sclerenchyma cells work like bones, which help provide structural support for our body.
In this lesson, we learned that the cortex is root and stem tissue found between the epidermis and vascular tissue of a plant. Depending on the type of cells present, the cortex might be involved in photosynthesis, food storage or structural support.