Plants have an amazing range of phenotypic plasticity. Meaning that they're able to take these basic structures, the roots, stems, and leaves, and modify them to gain a significant variety of functions. Now, I don't really want you to memorize any of this; I more just want you to get a qualitative sense of the breadth of morphological variety that plants can take on. So, let's start with roots. Now, we talked about adventitious roots before, which are those roots that are going to come from a stem. And there is a special type called a prop root, which is basically an adventitious root that props up the plant. It gives it aerial support. So these are modified roots that give the plant a little boost above the ground. Right here we have a picture of a corn plant, which has these prop roots, but these prop roots are also seen in, for example, mangrove trees, which live in brackish water and use the prop roots to kind of prop themselves out of the water. Go figure. Now, pneumatophores are generally advantageous that they don't have to be, and these are special modified roots that allow for gas exchange. You can see them in this image, all these little, they look like sticks popping up from the ground. Those are actually roots, technically they're pneumatophores, so those are roots that are doing gas exchange. Plants, again, like mangroves, have these because, for example, with the mangroves, they live in that brackish water, they still need to extract gas, so these pneumatophores allow them to pull gas out of the air by sticking up above the water.
Now, let's move on and take a look at some modified stems. So, for example, we have cacti. Right? A cactus is basically a stem, but it's been modified for water storage. Right? You know, it's the old myth, if you're stuck in the desert, find a cactus and drink it. I don't recommend doing that. Drinking from a lot of cacti will actually make you very sick, or maybe even a little more than that, see some crazy things, let's put it that way. Now, stolons are a type of modified stem that allows a plant to produce a new individual above ground. You can see an example of a stolon right here, this is the stolon, it's being kinda like shot out of the plant, and it where it lands, it produces a new individual. Sort of like the opposite of a stolon is a rhizome, and this is basically the same type of thing, a stem projection that comes out, this time it goes underground instead of going out above ground, and where it lands, it produces a new individual. Now, stems can also be modified into what are called stem tubers. Most notably, things like potatoes. Yeah. Potatoes are actually just modified stems, modified to store carbohydrates. And another structure you probably didn't realize was actually a modified stem, is a thorn. Thorns are just stems that have been modified into these defensive structures.
Let's lastly take a look at some modified leaves. Bet you didn't realize that an onion is actually a modified leaf. Yes. The layers of an onion are all modified leaves. It's called a bulb, and it's basically a leaf that's been modified for food storage. So, just like a stem can be modified into tubers, leaves can also be modified for food storage. And don't forget, earlier we looked at the example of a carrot, which is a root that has been, in some cases, in some sense, modified for food storage. Now, succulents are not only drought-friendly plants, and hopefully, if you live in a drought-stricken area, you'll replace your lawn with some nice succulents. But succulents have modified leaves that improve water storage. They're very often compared to cacti because of those similarities. You know, they have the same kind of, almost like feel to them. A nice example of a succulent is the Agave plant, which is what tequila comes from. Also, mezcal. Don't discount mezcal. Very underrated. Now, tendrils are another type of modified leaf. These are how climbing plants, like vines, are able to grip onto surfaces. So, they have these modified leaves that almost act like grappling hooks. Right? They wrap onto a surface and grip it, allowing the plant to climb vertically. There's also leaves that act as floral mimics, basically like pretending to be a flower. A perfect example of this is the poinsettia, which has these leaves that turn red to mimic the appearance of a flower, even though it's actually just a leaf, and this is done to help with insect pollination. There are also traps like the Venus flytrap. Right? That eat animals, those are also modified leaves. And lastly, cactus spines are modified leaves. So, just want to make a quick note here, remember thorns are modified stems, these cactus spines are modified leaves. So they may seem like more or less, the same structure, but they're coming from different sources. Now that's all I have for this lesson. See you guys next time.