Nonvascular Plants - Video Tutorials & Practice Problems
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Nonvascular Plants - 1
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Hi. In this video, we're gonna talk a little bit about nonvascular plants. Nonvascular plants or bryophytes, as they're technically called, are, plants that include mosses, liverworts, and hornworts. You can see a phylogeny of this right here. We have the Embryophytes, which includes, all the different types of plants we'll be talking about. And then here, we have our bryophytes. And you can see that vascular plants is a separate lineage. And remember that the, defining feature of these organisms is that they don't contain vascular tissue reinforced with lignin. Although some may have transport tissues that use cellulose to maintain their rigidity. You can see an example of moss, liverwort and a hornwort, right here. Don't worry if you can't really tell these apart, I mean, hopefully, you've seen moss before, if you've never seen or heard of liverwort or hornwort, not a big deal. These are just, you know, little, you know, low to the ground, very simple, vast nonvascular plants. Now, as we previously discussed, they have, gametophyte dominant life cycle, which is going to change in, later lineages to a sporophyte dominant life cycle. And these organisms are also homospores, meaning that they, the spores they produce are all of the same type. Some species have bisexual gametophytes, meaning that the, male and female reproductive, or the male and female gametophytes rather, are located in the same plant. Some species, like, mosses for example, have separate male and female gametophytes. So the male parts and the female parts are found in separate plants. Here we have, an example of a moss life cycle. And we can just kinda use this as a stand in for our nonvascular plant life cycle. So I'm just gonna quickly walk you through this image, jump out of the way here. So spores give rise to the gametophytes. Right? And here we have our male gametophyte, here we have our female gametophyte. And it's through mitosis that these spores will develop into the gametophytes. Here you can see we have the fully developed male and female gametophyte. And you might notice there's actually an error in this diagram. I didn't make it. It's really not a big deal, but, you know, here it says female, here it's male. You know, these arrows should be reversed. Sorry. I didn't make the figure. But it doesn't re it shouldn't really affect, your understanding. Obviously, the failed the female gametophyte spore is going to develop into the female gametophyte and the male gametophyte spore is going to develop into the male gametophyte. So just remember that these arrows are crisscrossed. Anyhow, these gametophytes are going to produce, the sperm and the egg. And remember that the sperm requires water to get to the egg. And the structure that produces the sperm is called the antheridium, the structure that produces the egg is called the archegonium, don't worry we're going to go over this again on the next page. So when the sperm and the egg get together, we're going to have fertilization, a zygote is gonna form, right, and that is going to develop into an embryo. And everything on this side, remember, except for the zygote here, need to note that zygote is 2 n, All this other stuff is n. Right? And it's it's indicated in, in the figure that these are all haploid. All this stuff, of course, except for the zygote. Right? The zygote's diploid. They don't actually show it in the figure, but when the sperm and the egg combine they're gonna form the zygote. So everything over here is diploid. Diploid. Right? So this is the dominant part of the life cycle. Basically, what that means is the the part of the plant we're used to seeing is going to be this, haploid gametophyte part of the plant. This embryo that forms after the sperm gets to the egg, this embryo is going to sprout into this sporangium. Right? So this embryo, basically, is going to develop into the sporophyte. And the sporophyte, part of the sporophyte is the sporangium, which produces the spores. And those spores, remember, are going to be haploid, and, the sporophyte produces them through meiosis. Those haploid spores then develop into the gametophyte and we repeat this cycle. So, you know, this is just basic alteration of generations. The things to bear in mind are that, water is necessary for the sperm to get to the egg. And those terms antheridium and archegonium, don't forget, we're gonna talk about those in just a moment. So with that, let's flip the page.
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Nonvascular Plants - 2
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So let's go over a bunch of terminology. Again, gametophyte, that's the gamete producing part of the bryophyte. Hopefully, that term is very familiar by now. And, in the case of bryophytes, because they have a gametophyte dominant life cycle, the gametophyte is the part of the plant that we're most familiar with. And remember, that bryophyte, gametes require water. Right? Water is needed to move the sperm to the egg. The gametangia is the organ or cell, in which the gametes are produced. And they're contained in something called a gametophore. Now, remember, that there is a sort of like male and female dichotomy here. So there, the gametangia can produce male or female gametes and if it produces, female gametes, then we call it archegonia. Right? That's the female gametangia and it's gonna produce egg cells. And this is where fertilization is gonna occur. Right? The antheridia is the male gametangia and that's gonna produce sperm which are gonna go to those eggs to do fertilization. Now, taking a look at our figure here, you can see the male and female plants. And here, this is what the top of our male plant looks like, that's our male gametangia. Right? This is our gametophore. And we have the antheridium and the sperm in there. So, the antheridium is the structure that's going to produce those sperm. This whole thing is our gametophore. Oops. And then, of course, here we have the female side which is the archegonium. So let me write that in. This is the archagonium. And it's gonium because we're dealing with a single single archegonium. That's the singular form of the word. Archagonia is the plural. And here you can see our egg inside the archegonium. And, as we said, those, sperm are gonna need water to get to the egg. Now, some species, as as we mentioned previously, some species actually, are bisexual. That is they, will have the archegonia and antheridia in the same plant. We call those monoecious. So that's just a, a monoecious plant is just one that bears the sperm and the egg in the same gametophyte. A dioecious plant bears sperm and the egg on separate gametophytes. So these mosses that we're talking about, these mosses are dioecious. Right? Because the male and the female parts, or male and female gametophytes rather are on different plants. And notice how in this figure it says nonvascular leaves, right, and nonvascular stem. This is a nonvascular plant, so it's going to lap those, vascular tissues, and it can't have, leaves in the sense that we're used to thinking of leaves because it doesn't have vasculature. So these are nonvascular leaves in quote, quotes. Also, technically, these aren't roots because, again, roots require vascular tissue. These are what are called rhizoids. They they're functionally like roots. They're very similar. The difference is that they don't have those vascular tissues, but they serve the same purpose. But we have to give it a different name to distinguish it. Now moving on, let's take a look at the sporophyte. So we just looked at the gametophyte anatomy. Let's look at the sporophyte anatomy. So the sporophytes in these nonvascular plants are gonna be the small structures. Right? This is the part of the plant where not you really, like when we think of moss or, you know, you probably have never thought of a liverwort, but if you were to, you wouldn't really be thinking about the sporophyte, you'd be thinking about the gametophyte of that organism. And that's because, again, these organisms have a gametophyte dominant life cycle. Now the sporophyte, that's the structure that contains the sporangium, which is what makes the spores. And the sporophyte has a couple features to it. It has what's called the foot. And the foot is basically the attachment to, the gametophyte and it absorbs nutrients from the gametophyte. And, then you have the ceta which is it's basically like the stock of the sporophyte and it's going to transport nutrients up from the gametophyte to the capsule. And the capsule is that top of the, the sporophyte and it's the, sporangium structure, basically. It it is the structure that contains the sporangium. You can see, another view of this here. We have the capsule, and you can see some spores being produced and coming out. Right? And of course, those spores are going to, grow into the gametophyte, which is sort of what's being shown in this image here. It's like the, the growth of the gametophyte starting out as a little bud with, you know, little bityrysoids and then growing into a full fledged gametophyte. And this, this early structure, which is really just a chain of cells that you see right here, that grows from the spore and develops into the gametophyte is called the protonema. And it's, again, it's just a little chain of cells that grows out of the spore and develops into the gametophyte. It's kinda like the sprout of the, nonvascular plant. Alright. That's all I have on this video about vascular plants. I'm sorry, nonvascular plants. So I'll see you guys next time.