Roots and Shoots

Hi. In this video, we'll be talking about the two major structures of the plant body, the roots and shoots. Now, before we get there, let's actually start by reviewing some of the plant anatomy we've already talked about. Hopefully you remember that plants are you carry, Ah, tick organisms that synthesized sugars by using sunlight energy to generate a teepee and then using that 80 p to carry out carbon fixation in the Calvin cycle. This process of courses photosynthesis that I'm talking about. And if you don't remember this or you feel like you need to review it may be highly recommend you go back and check out the videos on photosynthesis and the Calvin cycle. There also some videos on general, uh, plant biology. Let's just say that can cover some topics to maybe give you a little more background before this. Now moving on the chloroplast is the organ L in the plant cell that carries out photosynthesis. Usually there's many chloroplasts in there, not just one. Carrying out photosynthesis and chloroplasts are get their name from chlorophyll, which is the green photo pigment that plays a big role in absorbing sunlight. Energy. Now chloroplasts like the one we see here. Onley Take up a little space in the cell. There. Many need to fit in the cells. They don't, you know, uh, take up tons of room. However, plant cells have this large structure called the Central Vac You'il and Central Vac. You'll has a variety of functions in the plant cell. For one thing, it's filled with water, sugar, amino acids. Other stuff. Sometimes plant cells will sequester toxins in the central vac. You'll thio protect the cell from them, and we call this solution in the central vac you'll the cell sap. And in addition to just holding this material, the Central Vac. You'll also is responsible for maintaining a plant cells ter giggity right that rigidness that the cell gets now. The scent. The vacuole is only one piece of maintaining that rigidness. The other piece is the cell wall, which provides structure and protection for the plant cell. Now you might recall they're actually two types of cell walls. There's primary cell wall and secondary cell wall. Primary cell wall is made of cellulose and cellulose, you'll remember. Is that Polly Sacha ride and it, uh, this primary cell wall surrounds the plasma membrane while the cell is growing. Now, the secondary cell wall is only found in some plants. Cells and secondary cell wall is a thicker structure, and not only is it made of cellulose, it's made of lignin. Lignin is a polymer you might recall that's found in vascular plants, and it helps the cells in those plants maintain rigidity. It's also a very important component of wood, so that might give you a sense of the sort of ah hard material that results from lignin fication. Now the secondary cell wall will actually form after the cell has grown. So it's uhh You know, the primary cell wall is gonna form during cell growth. After cell growth, some plant cells will form that secondary cell wall. You might recall that plant cells actually have channels between them called plasma. Does Mata and these channels allow for the transport of materials between cells and cell signaling? So you can see, uh, basically, the image we have here is a blown up version of one of these junctions. Between plant cells, you can see the plasma. Does Mata create these channels between the cells? However, these plant cells still have their cell walls and plasma membranes. And, of course, one last thing that's worth noting is, um, this substance, the middle, um, Ella, mostly made of pectin, is kind of like a sticky goo that's gonna help glue these plant cells together, and you will find it on the outside of the primary cell wall. Now let's flip the page.

Hopefully you remember from our discussion on photosynthesis that plants need water, carbon dioxide and sunlight. You carry out that process. Water provides thes source of electrons. Carbon dioxide is the source of carbon, and sunlight is going to provide the energy needed for this process. In addition to these things, plants also need nutrients. They need nutrients like nitrogen, phosphorous, potassium and magnesium in particular, they need these things to build molecules and to maintain their Selves. Basically to lit. They'll die without these things. Um, hopefully you already are your brain years already turning. And you're thinking on nitrogen phosphorous. What could those be used for? Proteins, right? Proteins, nucleic acids to the backbone of nucleic acids Has all those phosphate groups proteins and nucleic acids filled with nitrogen. So, you know, thes nutrients are essential to the basic function of a plants cells. Now, usually these nutrients are obtained from the soil where they're found as ions. Right. So we're not just gonna see ah, plain old potassium sitting around. It's going to be like potassium with the charge on it. Um, of course, potassium is a cat I in, so it's gonna have a positive charge no plants absorb Uhh. You know these nutrients and water through their roots. And of course, they absorb sunlight energy through their leaves. And this absorption is going, or this need for absorption is going to play into the morphology or the appearance of those structures. So leaves have to absorb that sunlight Energy, right. They take the appearance of sheets. This is actually giving them a really high surface area to volume ratio. You might recall that that surface area to volume ratio has a huge effect on absorption. Uh, the higher that ratio, the mawr absorption is possible. So leaves being these broad, very thin structures have very low volume for a huge amount of surface area routes have a slightly lower ratio. Uh, their tube like structures. Right. So they're gonna have mawr volume two more volume compared thio their surface area, but they form a really diffuse network. So they do. They are able thio still generate a large amount of surface area for absorption. Now, the reason they need a little more volume is roots are also going to be super important in for transporting materials. Right, So you need a little space in there in order, Thio move stuff around effectively now. Storage structures which you know, can be found in routes, for example, like tubers where they you know the route will swell up with sugars or something like a carrot, for example, those air structures that are not involved in absorption. And that's why they will actually have the lowest surface area to volume ratio of these parts of the plants. No, uh, you can see the two major parts of a plant right here. We have the chutes and down here, the roots. And of course, you can also see that in this picture of a realtor tree over here, where the earth has been cut away so you can actually see all these roots below ground here. And of course, all these branches and the actual trunk of the tree itself are the shoots, the proverbial shoots. So the root system has a couple jobs. It's not just there to absorb water and ions from the soil. It also anchors the plant into the ground, which is quite important. I mean, you don't want to just blow away. If a gust of wind comes by, uh, roots can also storm materials produced in the chutes for later use. Think of carrot, for example. The actual part where eating is the root of that plant. I mean, this green stuff on top of the carrot, those air, the shoots, we actually eat the root of this plant. We don't really eat the shoots of this plant, Andi. That's because these routes are full of sugar. So they're delicious, right? And that's because they're actually being used for storage purposes, right? It's these green tops that are actually producing the sugars, and then they're being stored in Thedc Arat route. Now, when talking about routes, uh, it's important to get a little terminology straight. Uh, the main dominant route is called the Tap Root. Right here you can see the taproot. I'm drawing a line through it that is our tap root, and it's the dominant root from which all the other roots of the plant will project. Those other roots of the plant are things we call lateral roots, and here I'm going to draw a lateral root for a few lateral roots in red. So those are lateral roots. Now. It's important to note that not all routes are actually going to arise from, uh arise from like some taproot. Some plants are what we call Advantis cious. And basically, these have roots that developed from the shoot system rather than the root system. So here you can see the shoot of a plant. So that is the shoot. Right? And here are some roots sprouting from it thes structures. Right here. You jump out of the image. Sorry. You guys can't see what I'm pointing at. Those are the roots there sprouting off the shoot, making this an Advantis cious plant. Uh, there are a variety of plants that show this sort of morphology. A lot of vines are Advantis cious mawr famously, uh, fig trees send down these long, you know, tendrils from their shoots down to form routes into the ground. Very cool looking. If you've ever seen one in person, it's almost like a canopy of these aerial roots. Now let's turn the page

the roots main job is absorbing water and nutrients. The chutes main job is to absorb co two and light and to then carry out photosynthesis. The stem of the plant is the vertical growth structure. This is how the plant is going to reach its leaves up to get access toe light. And when we talk about the stem of a plant, it's important to get some terminology straight. There are these points on the stem we call with notes. This is basically the part of the stem where leaves and buds will grow out and the space between these nodes is called an intern owed. So basically, the stem of a plant is made up of a Siris of inter nodes and nodes. Now, at these nodes we have what is called a lateral, or sometimes an auxiliary bud. And you can see a picture of that. Here we have these little buds represented in yellow, appearing at the nodes of stem. Now at the top of the plant will have what's called the a pickle. Bud. You can see that up here. This image is labeled terminal, but this is also called the a pickle. But now this a pickle. Bud is the primary growth point of the plant. This is where the plant is going to basically grow upward from those lateral buds are where leaves, um, branches or flatters. Various lateral structures will develop so a pickle but is for vertical growth lateral but is for, uh, lateral growth. Now very quickly. Branches are special structure. That is a woody projection from the plant, not all plants or woody plants. So not all plants are going to have those woody projections. Some stems are non woody, so turning our attention to what grows on the stem. Let's look at leaves these air the organs, vascular plants that are the sights of photosynthesis and gas exchange. And they actually have two parts the petty oh, which is thestreet talk or this portion that connects the leaf to this stem. So this is petty ole right here, and then the other portion is called the blade like a blade of grass. That's really the portion we think of as the leaf, so to speak. Now the interior tissue of leaf is where the magic of photosynthesis, so to speak, happens. We call that area the Miso Phil So here. This is all miso, Phil, and you can actually see this layer on the outside. That's the cuticle, a structure we've talked about before That prevents water loss from land plants and also, you might notice here in the bottom, the guard cells thes cells around the opening in the leaf known as thes stone MMA, or stay mata as the plural form you see here. So those snow mata are the pores and leaf that control gas exchange and help regulate water loss. So uhh, they open and close based on the swelling or shriveling of the guard cells, which are these special cells that fluctuate there to ter giggity to open and close that poor that stone A. And you can see that going on in these images here, and actually the way these plants swell or shrivel is by moving potassium ions and water follows those potassium ions, so either they're drawn into the HVAC. You'll write the central Vac u ALS water follows. They get targeted. So here, there targeted, they swell up, and that pops open the port or the potassium ions. Leave the evac. You'll go to the extra cellular environment, drawing water out of the HVAC. You'll making those guards cells shrink and lose to tear giggity. And that causes thes Stoneman to close. All right, that's all I have for this page. Let's flip.

plants have an amazing range of FINA typical 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'm more just want you to get a qualitative sense of the breath of morphological variety that plants can take on. So let's start with roots now. We talked about Advantis cious roots before, which are those routes that are gonna come from a stem. And there is a special type called a prop route, which is basically a an advantage cious route that props up the plant. It gives it aerial support. So these air modified roots that give the plant ah little boost above the ground. Right here we have a picture of a corn plant which has thes prop roots. But, uh, these prop roots air also seen in, for example, mangrove trees, which live in like a brackish water and use the prop roots to kind of prop themselves out of the water. Go figure Now, new metaphors are generally advantages that they don't have to be, and these are special, modified routes that allow for gas exchange. You can see them in this image. All these little, uh they look like sticks popping up from the ground. Those air, actually roots. Technically there, Newman. Ah, fors. So those air routes that air doing gas exchange plants again like mangroves have these because, uh, for example, with the mangroves they live in that brackish water. They still need thio extract gas. So these new metaphors allow them to pull gas out of the air by sticking up above the water. Uh, now let's move on and take a look. A tsum modified stems. So, for example, we have cat die, 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 cactuses Will, actually CAC ty Rather will make you very sick Or maybe even a little more than that. See some crazy things. Let's put it that way. Now. Stolen zones are a type of modified stem that allow a plant to produce a new individual above ground can see an example of a stolen right here. This is the stolen. It's being shot out of the plant and it where it lands. It produces a new individuals. Sort of the opposite of a stolen is a rhizome. Um, 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. Air actually just modified stems modified to store carbohydrates. And, uh, 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. Uh, it's called a bulb, and it's basically leaf that's been modified for food storage. So just like a stem can be modified for food storage right with the 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 route 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 a modified leaves that improve water storage there very often compared, uh to capt I Because of those similarities, you know, they have the same kind of, uh, almost like feel to them. And a nice example of a succulent is, uh, the gave plant, which is what tequila comes from. Also, Moscow don't discount mescal. Very underrated. Now, tendrils are another type of modified. Leave these air how climbing plants like vines are able to grip onto surfaces so they have these modified leaves that almost act like a like grappling hooks, right. They wrap on a surface and grip it and allow the plant to climb vertically. There's also leaves that act as floor floral mimics, basically like pretending to be a flower. Uh, perfect example of this is poinsettia, which has thes 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's also traps like the Venus flytrap, right? Um, that eat animals. Those are also modified leaves. And lastly, cactus spines are modified leaves, so I just want to make a quick note here. Remember, thorns are modified stems thes cactus spines, air 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. I'll see you guys next time.