Tissues

hi. In these videos will be looking at the various tissues found in plants, tissues. You might recall our special collections of cells that usually air from a similar origin and have similar function and basically unite to carry out some specialized function of an organ. Now the first type of tissue in plants. We're gonna look at his vascular tissue, and we've actually talked about vascular tissue before when we talked about general plant biology. Now, vascular tissue transports water nutrients and the photosynthetic products around the plants. And sometimes these could be massive distances. I mean, think about a redwood tree, Those huge giants. Those plants have to carry water up from their roots in the ground, hundreds of feet in the air. I mean, it's mind boggling. Thebes distances that some plants have to transport various materials. Now, vascular tissue is grouped into what are called vascular bundles. You probably actually seen these before. For example, in a stock of celery. When you cut it, you can actually see the vascular bundles there, these little dots that you can see in the plant and these vascular bundles actually run the length of the stem, um, vascular tissue is usually broken into xylem and flowing. Xylem is the water conducting tissue. Uh, it brings water and dissolved nutrients up from the roots to the chutes. So this is uni directional. It's bringing this stuff up and on Lee up. It does not float. Bring water down, for example. There wouldn't really be appointing that, though, If you think about it. Waters absorbed in the roots It's needed up in the chutes and other parts of the plant, so the asylum on Lee has toe worry about bringing it up. Now xylem will be composed of what are called track kids and these air long thin water conducting cells that are found in all vascular plants. And they have what are called pits. Pits are openings in the secondary cell wall that allow water flow. Andi, there's Onley primary cell wall present in these pits. So in our diagram, let me actually jump out of the way here. You can see we have some pits labeled in our tray kids, and you can see them right here. There's another one right here, and these allow for water flow again. And in those pits there is no secondary cell wall right. None of that Onley primary cell wall at the pits? No. Some plants have vessel elements. Angiosperms specifically have vessel elements. Some other plants do too. But mainly they're found in angiosperms. And these compared to Trey, kids are much shorter and wider. Um, and they also have pits, but they have these special openings as well called perforations. So trade kids air kind of like long thin tubes. Vessel elements are shorter and wider. So think of it as a, uh, a tray kid as a thin pipe and vessel element as a very wide pipe. And these vessel elements have what are called perforations, and they're basically just openings in the cell wall that you can see here that allow for water conduction. And actually, because of thes perforations and the morphology, the shape of the vessel elements, vessel elements are actually better able to conduct water than Trey kids. Or I should say they're able to mawr efficiently conduct water than Trey. Kids now xylem also contain what are called fibers, and we're gonna learn more about this later, which are certain type of cell called a scaler, and came a cell. We're gonna learn more about these later to they also contain Parent came a sells for lateral transport of water. Right xylem are Their main job is to get water to flow up. It's gonna be different cells that transport water laterally around asylum. And we're gonna learn more about these two types of cells later on. Uh, and don't worry, we're gonna bring it all back together. So moving on, let's take a look at flow. Um, these air the other main type of vascular tissue and flow them conduct sugars, amino acids as well as chemical signaling molecules like hormones. And they are bi directional, right? They can, um they can conduct these things between the roots and shoots. They could go up and down flow more made up of what are called SIV tube elements. These are specialized. Parent came A cells that transport sugar and other elements, and they have what are called SIV plates. If we look at our sieve tube element here, which is going to be this cell, you can see the sieve plate at the bottom has a bunch of holes in it right that allow for the transport of various materials between cells. You also have called companion cells, and these support the sieve tube elements both metabolically and physically. Um, the sieve tube elements lack, for example, mitochondria. So these companion cells, they're going to keep them alive so they can keep doing their job. They the companions cells also helped produce membrane for the city of tube elements. So thes sieve tube elements really rely on these companion cells in order to carry out their function that let's turn the page.

epidermal tissue is kind of like the skin of the plant. It protects the plant from pathogens physical damage and also helps prevent water loss. Now epidermal cells will actually secrete this waxy film called the cuticle that helps prevent with helps prevent water loss. And you can see the in this image the water beating up on the surface of this plant because of the cuticle its hydrophobic and causes the water to beat up on the surface. It also prevents the water from leaving the inside of the plant. Now, sometimes on the epidermis of plants will find what it called. Try combs that air little hair like structures made of specialized epidermal cells. And they carry out a very wide range of functions. Um, they can be involved in water loss. They can help defend against herbivores by containing some sort of nasty chemicals like these air chemical. Try a combs here that are meant to prevent herbivores from eating the plant they cover. Uh, they can also help reflect sunlight, and in fact, they can even be involved in eating animals like we see here. This stock of the plant is covered in these. Try combs which are the little hair like things with the beads on the end. And you can see that these try combs have wrapped around this hapless insect here, which is now destined to become plant food. Ground tissue is the third type of tissue found in plants, so we have epidermal tissue, vascular tissue and ground tissue. And ground tissue is basically everything that is an epidermis or vascular tissue. So it's kind of the grab bag, but generally speaking ground tissues gonna be responsible for producing and storing important molecules for the plant. Generally, we can separate the ground tissue into two regions the pith and the cortex. The pith is going to be this inner region here, and it is basically ground tissue that's surrounded by the vascular bundles. Now what we're looking at, just to be crystal clear is the cross section of a plant stem right here. So basically, if we had a plant stem and I don't know, like, here's a little leaf coming off of it, you know, if we cut that across and then took that piece and were to look at it, look down on that cross section. That's what we're looking at right here. It's that interior layers, the pith. You're gonna find the cortex, actually, all the way out here, the layer marked six. This kind of dark layer on the outside. That's the cortex. It's the ground tissue outside of the vascular bundles. So this whole region in here, those air, the vascular bundles this region marked three is the asylum spelling it the French way there for the next 30 on the end. Kidding. And then four Here, this is the flow him and these are the vascular bundles. So the pith is the inside six. That's the cortex on the outside. And seven, What's labeled seven here is actually our epidermis, so the cortex can actually be broken down into, uh, certain layers itself. We have the Endo Durmus, which is the innermost layer of the cortex. So it's going thio form the cell boundary between theme the, um, the cortex and the vascular tissue of the plant. On the other side, we have the Paris cycle, which is a thin layer of tissue between the Endo Durmus and the flow. Um, so essentially, the if we were toe kind of zoom in on this image right here, we'd basically have the flow, Um, which is layer four. And then we'd have the Paris cycle, and then we'd have. Which is you can't really see here. It's not later. Five. Layer five something else, But you don't need to worry about it. So basically, just to make this crystal clear, let me jump out of the image and write this in. You have the flow him, the Harris cycle and then the Endo Durmus. And we're going deeper into the plant in this as we go along this way. All right, let's flip the page and talk about some of the specialized cells of the ground tissue system.

ground tissue is made up of three special types of cells. Parent came cells are the most abundant cells in plants. They form the pith in the cortex of stems, the cortex of roots and the masonville of leaves. Uh, many of these parent kinda cells are toti potent, which means they can develop into any type of cell at any time, basically, and that's why they're going to be involved in healing as well as a sexual reproduction. In fact, speaking of healing, sometimes you'll see what's called a callous. This is basically a massive, unorganized parent. Came a cells covering a wound, right? So these guys are gonna rush onto the scene and develop into the necessary type of cell and help seal up that wound. But you also see parent came a cells act as rays, which we mentioned previously. These radiate through the vascular tissue to transport the water and nutrients laterally. Remember, we said that the xylem are responsible for vertical transport. These guys air going to help them out by doing lateral transport. There's also colon kinda cells. Thes basically are just there for structural support, and they really help out in growing parts of the plant. So growing shoots and leaves, you'll have these colon chema cells providing structural support. The reason their favorite and growing areas is because even though there you know, they have these thick cell walls, they're very structurally sound. They're actually still very stretchy and flexible. So while the plant is growing, thes can provide structural support but not hinder the plant's growth by being too rigid. For example, Sklar Square and Kinda cells as a mouthful to say that provide structural support. Similar to Colin came a cells, but they provide structural support in places where growth has ceased and generally speaking square and Kima cells are dead at maturity. So these basically have a thin primary cell wall in a very thick secondary cell wall made of lignin and cellulose, you'll find squaring came a cells as fibers, which we previously mentioned. Um, thes fibers will run along the asylum, for example, and help provide structural support. You'll also see squaring kima cells called UH square IDs, which basically have really thick lignin walls and form a protective coating on like seeds and the shells of nuts, for example. So these guys have, like, extra beefed up Thio form a really hard exterior coating on plant structures, whereas the fibers arm or involved in structural support on in the tissues of plants now putting this all together. Here we have all of the types of cells we've talked about. The xylem, the flow, um, all next to each other with their support cells, like the square and kind of fiber, which again is going to provide structural support. We've got a parent, came a cell. You know, that could be like a ray that's providing lateral transport of water and nutrients. We also, of course, have our colon kinda cells that are going to provide structural support in growing sections of the plant. All right, that's all I have for this lesson. I'll see you guys next time.