hi everybody and welcome back to miss Angus biology class I am Miss angler and in today's video we are going to look at plant tissues um specifically I'm going to show you how to identify them how to make it really easy to study for exams because I know tissues all look the same and especially plant tissues it's so hard to tell the difference there's so much to remember I'm going to make it really easy I'm also going to break down their functions that you know what they do and finally I'm also going to show you what they look like under a microscope so that you know in an exam what it looks like in a diagram form or in a micrograph now if you are new here don't forget to give this video a thumbs up and subscribe and make sure your notifications are turned on because I post Life Sciences content for grades 10 to 12. all right now let's just quickly break down the plant tissues and then I'm going to go into more details so tissues come in two forms they either come as a meristematic tissue which is tissue that is temporary and doesn't hang around for very long in a plant it's where growing happens whereas permanent tissue is as the name suggests lasts longer and technically meristematic tissue becomes permanent tissue over time and that particular permanent tissue can be things like parenchyma collinchyma sclerenchyma and I'm going to go through all of those soon now as well as the vascular tissues which is xylem and phloem so let's begin with looking at the Mary stems now the Mary stems are tissue that grow and they differentiate into any kind of tissue and we find them in two major regions we find them at the tips of a shoot or the tip of the root which is what we call apical Mary stems and then the second location is lateral which means we actually find it here in the stem and it is responsible for a slightly different kind of growth and if we look over on to the side here apical Mary stems or the merry stems we find at the tip they cause primary growth and they cause the lengthening of the plant and so what that means is the apical Mary stems are responsible for plants growing up towards the Sun but also the roots growing down towards water and soil now the lateral Mary stems on the other hand they are there for secondary growth and they occur in something called the cambium when we move on to the next section when we do plant organs I'll explain what plant cambium is but essentially it's this when you want to make a plant like a tree or even just a shrub or a bush you want it stems to become thicker the cambium is a ring of tissue that allows you to grow in width in other words one year may be the width of your stem is this size but due to lateral Mary stems two or three years later it could be this wide and that is because the lateral merry stems have grown in thickness the second thing it also does is it provides bark on trees and that does make sense because every time you get a little bit wider you know like the width of your stem increases you're going to have to add on a new layer of bark Now we move on to the epidermis which is the first of our permanent tissues now the epidermis in this picture is grouped together with a lot of other cells and tissues I just want to point it out if we have a look here if we look right at the surface we see there is a label here that says cuticle and then it says upper epidermis and you've actually got a lower epidermis and then a lower cuticle down here and so what I'm going to talk about is those first two the cuticle and the upper epidermis so essentially the point of any epidermis is protection okay so we're trying to protect everything that is below it and we also want to make sure that all the tissues that are sitting underneath it which is basically everything down here in this curly bracket where it says mesophyll we want to make sure that those cells can do their job and so the point of specialized epidermal cells comes into play here now what is the point of the epidermis and what is near it or on it that helps it do its job well we've got two things here first of all when it comes to the cuticle which is this structure over here and if you can't see what it is it is actually the see-through layer that's sitting on the top of a plant a waxy cuticle is literally made out of wax and it prevents water loss the other thing that's really important about the actual epidermis itself which is this middle layer over here I'm just going to color in one of the cells in Black you can see that is an epidermal cell this whole thing you'll notice there's only one cell layer thick there is one next to each other so here is another one next to it and there's another one but you'll notice there aren't any underneath it there are other cells underneath it and the reason for that is you want to be able to get as much sunlight moving from the waxy cuticle down through the epidermis and you want to get it into these other underlying layers and so you want it to be transparent and that is also the waxy cuticle being transparent allowing for sunlight to penetrate into the lower tissues now some of these epidermal tissues are specialized for example if we look at the lower part of this diagram where it says stoma and guard cell those are specialized cells that I'm going to quickly point out called the stomata now in preparing for your tests or exams you may be asked to draw a picture like this draw any of the cells and label them this particular diagram is putting many tissues together but you are going to have to learn this diagram at some point because it comes up in the plant organs section which is after plant tissues now as I mentioned you get specialized epidermis tissue and in particular we are looking at the stomata the stomata are the little openings that are on the underside of the leaf and what you can see here is what we call a guard cell and there are two and literally they guard the openings of your plant and they make sure that certain substances can come in and certain substances can come out and they do that by using their vacuole and basically their vacuole fills with water or cell sap or it empties and that's what opens and closes the stoma or this opening in the middle you'll see here is the stoma open and here is the summer closed by the way the word stoma should not be confused with the word stroma s-t-r-o-m-a the stroma is the filling inside of a chloroplast now the final specialized epidermal tissue is the root hair cell you will find these cells growing on the surface of the roots now you can't actually see these These are microscopic and as you can see I mean this is an example there's the sides of the soil particle and there's the size of the root here it's very very very small you can't actually see these but you'll see that it's got this really long elongated um structure to it and in actual fact what it's doing is it's pushing it's um vacuole down into the elongated part so you can actually see here is a normal size vacuole along size so there it is if I just do a little upline whereas this particular one goes all the way down and then it comes all the way around you can see it's very very large and so what they've done is they've elongated their vacuole down so that they can make this long root hair now why do we do this well root hair cells have two functions um the reason that they have these two functions is to improve the surface area of the plant because you want to absorb as much nutrients from the soil as possible and the second thing is you want a nice large vacuole not just to help with the root hair but to help store the water or the minerals that are actually coming in and then once they're in the plant then you can determine where they go we're now going to move on to the next kind of permanent tissue which is our ground tissues starting with parenchyma or parenchyma depending on how your teacher says it and these are the most abundant tissues in Plants we see three different kinds and I'm going to go through how to identify them and their functions now starting off with parenchyma looking at parenchyma we need to be able to see it in a diagram and in a micrograph and we need to look for two things when we identify the first thing is it must have a thin cell wall which we can actually see very clearly in the micrograph over here it's a very thin cell wall and also we're looking for intercellular airspaces which again you can actually see in the micrograph really clearly it's these little spaces in between and if I color them in there is an intercellular airspace there's another and there's another if we look at the diagram often what you see is this kind of picture over here and it looks like they're irregularly shaped so sort of round rectangular shaped cells and it links back to their purpose their shape remember shape equals function and if we look at their functions it actually makes sense why they look the way they do they are what we call the packaging tissue which means that they give the body like sponginess and softness and flexibility and so being these like circular shapes does that and having spaces in between them makes them more spongy they're also where we store things you'll notice they look quite empty I mean if you look at the micrograph there's nothing really inside of here and that's because they need a lot of space to store stuff now the intracellular airspaces allow for gaseous exchange because it's where gases can can literally Exchange in that empty space and it also allows for meiosis because again you need an empty space for water to move through and so that's what parenchyma or parenchyma does for plants now a special mention for parenchyma that has chloroplasts in it because I want to point out regular parenchyma doesn't have any chloroplasts in it but a special mention for parenchyma who does we call them chlorine chymer and literally they've changed their name because their normal parenchyma but now they've got chloroplasts inside of them which means they can photosynthesize and this often is the parenchymen you can see on the surface of a stem that's what makes the stem green and fleshy the next tissue is Colin kymer and um collenchymers sometimes is confused with parenchyma because they look very very similar let me show you how to tell the difference between them so when we are trying to identify them we're looking for two things number one we're going to look for these thickened corners and if you have a look down at this micrograph you can see here the corners are unevenly thickened in other words if you even compare it to this one over here that's a very very very thick corner now other than the thickened Corners you'll also notice that the corners are definitely unevenly thickened you'll notice that one side of the cell will be really really thin and then maybe another side of the cell will be much much thinner so you're looking for that uneven look um and that's pretty much the easiest way to identify them and if you look at our diagram at the top here if they gave this to you in an exam what you're looking for and you can see it quite clearly here is it seems as though the cell wall doesn't sit perfectly around the cytoplasm in the sentence because it's so unevenly thickened so you're looking for that unevenness around the cytoplasm on the inside now this thickness has a function because remember shape is function and so if we look at our functions in Colon Kyla we can see a couple of things one we can see that it provides support and strength now Colin Khan is able to do this because its walls have been thickened with cellulose and pectin and now these walls are thicker but they still have flexibility so it means that we can still have like soft bendy green stems the stems haven't made the transition into a woody stem just yet and most importantly they are still green and they'll be able to photosynthesize which means that Colin kymer does have um oroplas in it as well our final ground tissue is going to be our sclerenchyma now sclerenchyma is the thickest of the tissues sometimes again this one is a little bit confused with Colin kymer but you've got to look out for one main important detail and that is when we are trying to identify them they have evenly thickened walls and if you look alongside here at our micrograph you can see that the walls are much more evenly thickened all the way around you'll notice that it's not like slightly thinner on one side and then slightly thicker on the other as we saw in Colin Karma it's evenly thickened it's even more clearly seen in the diagram here where the thickened walls make more of like a geometric and consistent or uniform pattern now sclerenchyma's functions are divided into two depending on where you find them the main function of sclerenchyma is to provide rigidity and strength which means that you want to keep things upright and stable we find this in a lot part of our roots and our stems and our branches and this is where we find wood and scaram Karma is actually divided into two if it is a sclerenchyma that's a fiber we are going to see it in wood and bark of a tree and that's what you can see alongside it these are what our fibers look like when you cut them in half and you can see on the inside clarids on the other hand are another kind of sclerenchyma and these scleros are found in nuts or stone fruit so the shell of a nut or the pit of a stone fruit on the center and they look a little bit like the one that we have alongside but if I were to sketch it for you essentially the main difference if we draw them is sitting on the inside if that is the outside of the cell wall it seems like they have these like pinched in centers that have these like little arms that stick out and um they seem to look like their cytoplasm has like fallen in on itself like it doesn't have a cell wall or a cell membrane anymore and the reason for that is sclerenchana out of all the uh ground tissues is dead all the other tissues are living Scar and climate most importantly is non-living or should I say it's rather dead it was alive and now it has died now let's move into the final set of tissues which is the vascular tissues these are the transporting tissues that we see in plants and they are very specialized in their structure and they are xylem and phloem now let's run through xylem first of all you may be familiar with xylem you may have learned it in previous grades it transports water and it's got a very specific structure if we focus in on the main structure points of xylem it has elongated cells which means they're like long and thin a large Lumen literally means that the whole or the opening is quite large in other words it's quite big so that's a large Lumen versus a smaller lumen they're dead and empty um and so there's nothing inside of them there is no cytoplasm there is no organelles and that would get in the way of transporting water their cell walls are thickened with lignin and they do that because of the water pressure the water is really like strong so it pushes up against the wall of the xylem and you need to keep it um stable and lastly they have pits for lateral water movement and if you have a look alongside on the diagram you can actually see some of the pits which are these little openings and they've actually labeled them on the diagram as well those are the pits and that allows for lateral water movement so you can move from one xylem vessel to the next so the overall function of xylem is simply to transport water and minerals in One Direction this is important only in one from Niche from the roots to the shoots and xylem vessels can come in two different structures um basically xylem comes in two different shapes if you will and we call them either vessels or tracheots vessels are round and elongated whereas trackids are spindle and what spindle means is that they sort of like taper off at the end and so if I were to draw that for you so you can see what I mean a vessel would be like a round shape like that like a long tube right like a cylinder whereas a tracheid would um be long as well but the ends kind of go pinch in they like taper off like that so that's a slight difference between the two and so that's why I call them round or spindle and then the way they are arranged so here they say end to end which is what our vessels are so what that means is that wherever one vessel ends another one is stacked on top of it like that whereas overlapped it means that the tracheids the nature of their shape where it's pointy at the end it means they actually need to be overlapped so they sort of like sit like this on top of each other so they overlap and that's how you can tell the difference between the two now let's look on to phloem which is like the sister to xylem and they do have a lot in common in terms of their physical appearance but there are some very defining structural things that I want you to look out for something that phloem does share with xylem is that it is also arranged end to end so it's stacked on top of each other and you can see that um quite nicely actually alongside here you can see the cells stacked on top of each other so here is one stack and here is the next and so those are stacked onto each other and that's what it means to be overlapped but then they have the structure which makes them very unique which is this structure over here called the sieve plate the purpose of the silver plate like any sieve is to filter out make sure that there's any like large pieces of sugar that it is flattened out and so that it can move more freely because it can great it can get quite like goopy and sugary like syrup so you want to keep it flowing quite well and the last thing which isn't in this diagram here but but alongside um phloem cells they have companion cells which are essentially cells sitting alongside um these are just regular like parenchyma cells they're not necessarily any companion cells but they could technically be comparing companion cells as well perhaps but essentially what they do is these companion cells sit alongside our phloem cells and they provide phloem with all the nutrients it needs to survive all of the mitochondria and energy because you don't want any other organelles in the way you want to keep the phloem empty so you don't want any organelles there so you put it in a little Companion now as to the functions of our phloem when we speak about the function of phloem I think we already know it transports sugars and it's a two-way movement which means that sugars are going to go from the bottom up so from the roots to the shoots but they must also be able to go from the leaves where they're ultimately made down to the roots to be stored later so that's also another defining difference between Xylo and phloem is the move movement of substances and that's it for today's video I hope you've enjoyed it make sure you are subscribed and your notifications are turned on I'm constantly growing the grade 10 playlist so keep checking back and that's why you need the notifications to make sure you get the newest content every Tuesday and Thursday and I will see you all again soon with many more plant videos as well as other grade 10 topics bye