Primary Meristems

by Jason Amores Sumpter
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Hi. In this video, we'll be talking about plant growth, and we'll be focusing in on the various marry systems that plants use now. Most plants experience what's called indeterminant growth, that is, they grow throughout their entire lives and that growth is not terminated. Now plants grow using what are called Mary STEMS. This is a collection of plants stem cells that is able to produce daughter cells and differentiate into any of the necessary mature cell types, meaning that these stem cells conform any of the necessary tissues and structures within the plant. Now primary growth as opposed to secondary growth that we'll talk about a little later in this lesson is when the plants X. When the plant extends its roots through the soil or grows, it's shoots to increase light absorption. Sometimes this can mean sending the shoots down vertically or the stems up. I'm sorry, sending the roots down vertically and sending the shoots up vertically. However, sometimes it's about creating a mawr diffuse root system or shoot system. For example, if there's nothing competing for light above the plant, it might actually send its shoots out to create a wider surface area for sun light absorption, almost like creating a bigger solar panel. You could think of it as now. The a pickle Mary stem is going to be the merest M located at the tip of each route and shoot. And we call the a pickle mayor stem in the shoot. Very creative name. Shoot a pickle, Mayor stem. This gives rise to things like leaves and flowers. And of course, we'll seen you. Stems coming from this. And the route. A pickle marrow stem gives rise to spoiler alert Roots. Here, you can see an example of a shoot a pickle marry stem. We have this little nub, right? And here, that is our Technically, this is our shoot a pickle, mayor stem, And you can see it's surrounded by these young leaves right here. And if we actually take a look at the image over here, you can see that we have our little April marry stem in here. Right? That's gonna be our shoot a pickle, mayor stem. And then over here, get my head out of the way. You can see that, uh, these little regions in the center those our our shoot a pickle mayor stems and surrounding them are these young leaves, so that's actually a young leaf. So moving on, let's actually go ahead and talk about what are called the primary mirror stems. You see these? A pickle Mayor stems will actually differentiate in or to let me say that a different way. Uh, these primary marry stems that air going to form the various tissues of plants differentiate from the A pickle Mary stems and these primary mayor stems are the mayor stems responsible for primary growth. They come in three flavors for our three tissue systems, right? We have the proto durm that's going to give rise to the epidermis. The pro Camby, um, that's going to give rise to the vascular tissue and the ground marry stem, which you guessed it is going to give rise to the ground tissue. So let's take a look at these two figures here on this side. I have a shoot, and on this side I have a root, and let's actually take a look at some of these Mary stems. So the proto Durm, since it gives rise to the epidermis, should come as no surprise that it's found on the exterior of these structures. So this exterior layer of cells here and also on this side had exterior layer of cells and the exterior layer of cells over here is our proto durm, and that's going to give rise to our epidermis. Now the pro Camby, um, which is going to give rise to the vascular tissue, is found inside the proto dream, writes. The program is going to be the most external air. And the pro Camby, um, is going to be a more internal air. And we can see our pro Camby, um uh, in our route as the most central area. This, like core area here and in our shoot, it's actually gonna be this. You can kind of see this darkened line that kind of goes through the middle of the structure here. That's our pro Camby. Um, right that's going to develop into the vascular system now. Lastly, we owe actually, before I get to the ground, Mayor stem really quick. I do want to say that the pro campeon will actually also develop into what's called the vascular Camby. Um, and cork Camby. Um, these air, actually, other types of marist, um, so the pro Camby, um directly develops into vascular tissue, and it also develops into these other types of marry stems that are technically lateral marry stems. And we're gonna talk about those in just a moment. So don't worry. We'll get to that. So let's finish up here with our ground Mary stem and remember that the ground mirror stem will give rise to the ground tissue. And this ground tissue is basically the tissue that's not vascular tissue and not dermal tissue. So it's the everything else stuff, and in our route, it's going to be a the stuff found in this internal area here, of course, also over on this side. I'm just not drying it all the way across and in our shoot. It's actually going to be found in this region as well as this region in here. Um, the you might remember that in the chutes we have the ground tissue divided up as pith and cortex. Right? The stuff that's in, uh, inside the vascular bundles and the stuff That's exterior to the vascular bundles. Well, that's why our ground mayor stem has found on the inside and the outside of our pro Camby in there. All right, with that. Let's actually Oh, my gosh. Let me get my big head out of the waste. You can see where I drew. I'm sorry, you guys. Yeah. So our ground mary stem in the roots. Pardon my fat noodle. You can see that it's this internal tissue here. And I was just drawing it in over here on this side just to be clear that, you know, these things are occurring on both sides. So just to be super crystal clear, let me put some green over here. And just like all in there, that's all ground. Marry stem. Cool. Now let me get my big fat head in the picture and say, Let's turn the page.