hi everybody and welcome back to miss Angus biology class I am Miss angler in today's video we are going to be looking at plant organs now it is at this point that if you are not so certain about plant tissues you should click the video now at the top right hand corner go watch that video and then come back here the reason for that is you need to know all the plant tissues and their functions and structure before I can apply and show you how they make these organs now if you are new here don't forget to give this video a thumbs up and make sure you are subscribed with your notifications turned on because I post every Tuesday and Thursday so let's get into the video now breaking down our plant into two major systems the first system is above ground which we call the shoot system this is where we're going to go through the structures that we see in the leaf and the stem and then we're going to go into the root system which of course is exclusively The Roots as well as the outgrowth called the root hairs now remember it's really important that we understand that there is a difference between a plant organs above and below ground and sometimes there are certain structures or tissues that have slightly different roles above or below ground now before we go any further in this section we do need to recap the three main tissues I'm going to talk about throughout this video and I'm going to apply these tissue types to each of the organs so you know how they work now remember these are organs which means they need to be made up of many different tissues working together for a common cause so the first group of tissues that we want to go over are going to be the dermal tissues now you may remember the dermal tissues as these are the tissues that are responsible for covering the outside of our plant we see this on the stem the leaf and The Roots now these dermal tissues can be specialized as we see as our example here we can get something like stomata which is a special kind of dermal tissue and it is adapted for a very specific function but I'll get into that later the next kind of tissue type we need to just quickly revise over is vascular tissue now vascular tissue comes in two kinds and vascular tissue is either going to be xylem for water or phloem for food it's also important to remember that this is what gives the plant structure and support it's also the transportation tissue and as we can see with the arrows in this diagram xylem goes in one direction from The Roots up only whereas phloem can go both down and up because it's transporting food now the final group of tissues we are going to look at is ground tissues please don't be confused by this name it doesn't mean that these tissues are in the ground or underground they are simply the building tissues or they provide the foundation that we build our plant off of hence ground building from the ground up and these tissues generally fall into three major categories they are parenchyma calling timer and sclerenchyma please remember you do need to be able to draw and label and tell the difference between these tissues and exams and tests as well and you also need to know the differences in their functions based off of their structures now when we just quickly go over the different variances for their functions remember that parenchyma is the packaging tissue so it's big cells we've got Colin kymer which is the structural support but not as hard and rigid generally we see this in a stem it's often green and filled with chloroplasts as well and it's got thickened corners and then finally we've got sclerenchyma which is the very very hard connective tissue that we have in Plants it's what forms things like the husk of a seed or the bark and the wood of a tree and it has very thickened cell walls all the way around it now each of these tissue types are going to be explained for each of the organs in other words for every plant organ you must know the dermal tissue that is present the vascular tissue that is present and the ground tissue that is present and it varies from organ to organ so let's begin with our first organ of a plant which is of course a leaf or leaves now leaves are really important because they are like our solar panels right they are trapping the sunlight they are absorbing it and they are using it for photosynthesis and they've got a lot going on inside of them each of them having a very important function now this is a diagram of a 3D image of a leaf that we have cut open so we can see it on the inside and I'm starting off with something called the cuticle now the cuticle is a see-through translucent covering and it's most important function is that it is there for waterproofing now waterproofing is really important because you need to prevent water loss due to heat and that's what the cuticle does it's also clear which means that it allows sunlight to move through the cuticle and into the upper epidermal layer which we see here and now and that brings me to the next layer which is of course the epidermis and the epidermal tissue if we remember is the tissue that is responsible for protection now the um upper epidermal layer doesn't necessarily have any color to it either and it often is there as a protective barrier the most important thing about this also is that it is one cell layer thick so it's not a very thick layer but it acts as the skin or outer layer now sitting just below that is something called the mesophyll now the word meso means middle okay and the mesophyll is made out of two kinds of special cells one is called a palisade cell the other is called a spongy cell now we call it a palisade cell because like a palisade fence all of the cells are elongated like rectangles and they sit side by side the spongy cells or the spongy mesophyll are the irregular shaped cells that sit just below it now their shapes are really important in the way that they are put together because it influences of course their function so let's just quickly speak about Palisade cells Palisade cells are stacked the way they are and they're stacked standing up because you want to be able to put as many cells next to each other as possible now what's also really cool about Palisade cells is that the chloroplasts can actually move inside the cells and so what they often do is they accumulate near the top end of the cell so they can be closest to the sunlight spongy mesophil cells which are these cells that are lower down and on our diagram they are these lighter green cells that we see over here they are more of the packaging tissue they are a type of packaging tissue that is used often for water and for water evaporation but I'm going to get more onto that in another video where I go into the transportation and support systems of plants the next thing that we see inside our leaves is of course the next group of tissue which is our vascular tissues we have got our xylem and we have got our flow now remember these are running through veins in leaves which I'm sure you've seen before and that's what this entire structure is over here what are they transporting they are transporting all the products of photosynthesis so when we are photosynthesizing we are taking all of those carbohydrates and we are moving them around to the plant and that is moving in the flow the xylem on the other hand is bringing water all the way up from our roots to the leaves so that we can use that water to photosynthesize and that water is going into our meso fill now our final underside of our Leaf again has a repetition of structures we've got the lower dermis and the lower cuticle this is on the underside of the leaf but now we've got a really important extra modified epidermal tissue which is this over here it is the stomata now the stomata is a modified epithelial cell and you actually have two cells that sit side by side and they look sort of like jelly bean shapes and what happens is they have really really large vacuoles on the inside so this little black area here is going to be my vacuole and what we do is we fill that vacuole up with liquid or we drain it to make it open or closed now right now this stomata is open whereas this stomata would be closed and that's how we open and close the stomata to allow specifically gases but also water to leave the leaf as byproducts of photosynthesis now all of this is going to be even more elaborated when I move on to transportation and support within plants the next structure I want to move into is stems now there are more than one kind of stem actually there's a monocot stem and a dicot stem I'm specifically going to focus in on dicot stems it depends on the school and the curriculum that you're doing but the majority of us are only going to learn about a dicotyledonous stem which is what you see here and I automatically already know it is a stem for a couple of reasons one of course before we go any further look at this shape okay this is a cross section through a stem and we know that stems are generally like a cylinder right the next thing I know and I can confirm that this is a stem is because of these egg shaped bundles of tissues they sometimes look like eggs or maybe sometimes they also look like an acorn from a um oak tree depends on how you see it but that is the defining thing to say this is a stem now while they're making such a big deal about this is because when we go onto Roots just now well you might confuse stems with roots so this is what it looks like we have little bundles of tissues in a circle around the center and that's how I know I'm dealing with a stem now let's go into the various tissues again every single one of the tissues we've covered must appear here so starting off with the epidermis now a stem does have an epidermis and this epidermal tissue sometimes contains chloroplasts often it is in the colon climber which sits just below the epidermis and that sits inside the cortex now the cortex is the filling of the stem and as I said to you now it can contain Colin kymer now if Colin kymer has chloroplasts in it we call it chlorine chymer and that's what gives a stem a green look to it and so I want you to imagine that this whole entire area here where it's got that stripy green detail that is all going to be the cortex now sitting beyond that or as I mentioned to you earlier these little units of tissue and it is made out of our second category of tissues which is the xylem and the flow and these are our vascular tissues now as it may already be very obvious stems are conductive tissues in other words we are moving things from the roots and the leaves up and down and so that's why it's really important that these vascular bundles or this xylem and phloem appears and so in many textbooks we refer to these little egg shaped structures as a vascular bundle and that's what it is together it's really important to everybody that you put the phloem on the outside and the xylem on the inside it's really really important so we've got the water transportation on the inside and the food Transportation on the outside it will be very clear again why that is happening once we get to transportation in Plants now the final two things I want to cover is this white inner ring and it is called the cambium now cambium is a type of tissue I didn't recap earlier but you may remember this from learning your other plant tissues a cambium is a merry stem and Mary stems remember are able to turn into things so it means that they can change they can differentiate and this cambium is what is allowing the stem to grow and widen and thicken but it can also sometimes become Bach and we'll get into that a little bit more later on again once we go into more detail into plants but the basics is that cambium allows 4 lateral growth in other words taking a narrow stem and making it much wider now the final final Final tissue we're going to go over here is the pith the pith is all this Central tissue that sits in the middle here it is mostly ground tissue think things like our parenchyma it's quite fleshy and green um and as plants age and change and maybe this stem is going to become a woody stem the Perth the cambian and the cortex all slightly start to change consistencies but for now I'm only talking about Green fleshy stems so we'll stick to the pith being made out of parenchyma now we're going to move on to our last plant organ which are roots and roots are incredibly specialized like leaves and so it's important to know those specialized tissues now I also want to remind you that you do need to be able to tell the difference between a root and a stem and you can see here that the root diagram is very similar to a stem because remember a stem has those vascular bundles of tissues going around in a circle and then they have got the cambium which runs through it's like an inner circle you can see the pictures look very very similar but the main difference is remember those vascular bundles they are divided into half the top half having the phloem and the bottom half having the xylem if we have a look at the diagram alongside that is actually not the case but before I get to those let's make sure we start from the outside and work our way in now I'm going to start off with these routes now root hairs are really important because they increase the surface area that is why we have them and we need to increase the surface area so we can absorb more now potentially you will be asked to draw a root hair and this is sort of what a root here looks like we've got our nucleus up in the top corner and what makes root hairs unique is that they have a vacuole which is what I'm drawing now which goes the full length of your um root hair and the reason why you have the vacuole there is to create a osmotic difference in other words a difference in water so that you're constantly pulling water in all the time and remember that's the main function of roots is to Anchor but also to absorb water and minerals now sitting just inside of that is again the cortex layer and the cortex layer remember is made up of all of those ground tissues now potentially there will be two kinds of ground tissues here we'll have parenchyma but we'll probably also have Colin kymer too now a quick side note will we ever find chlorine chymer in a root no we will not because Roots do not have chloroplasts because they cannot photosynthesize because they are underground so just keep that in mind and actually something I want to go back to before we go any further I forgot to mention this about our routers our root hairs they do not have a cuticle so on the outside there is no cuticle now this makes sense because what do cuticles do cuticles waterproof now why would you want to make the cell that is responsible for absorbing water waterproof the answer you wouldn't want to do that you want your root hairs to absorb as much water as possible so root hairs have no cuticle on them now let's move in to our deeper layers and we're going to go into the endodermis now the endodermis is as it suggests Endo means inside and dermis means skin it is a layer that is very specially functioning to funnel water in other words cause water to flow in a certain direction now what's not in this diagram which we do need to know which is found just below the endodermis or part of the endodermis is something called the casparin strip now the kasparian strip is a waterproof layer that makes sure water gets where it needs to go now again I'm going to elaborate this more when we do transport of water in Plants but essentially water is going to go from the outside soil into the root here through the cortex through the endodermis around the casparin strip and then into the xylem and it's this casparin strip that is waterproof but it doesn't make sense now why there's a waterproof layer on the inside but don't worry the upcoming video will explain that too we then have Sitting below that as we've mentioned before we have our xylem and we have our floamed Asylum there's our phloem and you'll notice there again in different locations the phloem is now sitting on the center and the xylem is in red sitting in them right right in the middle of our diagram and along the edges now the last and final thing that I want to bring your attention to is something called the pericycle and also the vascular cambium so I'm actually going to put these two together um the pericycle is again where we have growth and where we are going to affect water movement and the vascular cambium as we mentioned earlier cambium means it is a merry stem it is growing and it potentially will change the type of tissue it started off as and so vascular cambium is essentially a merry stem that turns into more vascular tissue now as always I like to finish off my lessons with terminology recap remember you can use these to create flash cards which makes studying so much easier and you will definitely get more marks by using the correct terminology in your explanations now as you can see there was a lot of terminology so let's quickly go through them all we spoke about the tissue types in the beginning and we spoke about the outer layer being called the epidermal tissue this is the single layer of cells that sits on the outside of a plant it's there for protection and it is specialized in leaves and in Roots we then spoke about ground tissue which was that special packaging tissue that fills up the majority of the plant it gives its shape but also support examples of it we'll speak about just now but they were things like sclerenchyma and Colin kymer we then spoke about vascular tissue which was the xylem and phloem they are the ones who are transporting substances within plants we then moved on to specific structures like a cuticle and a cuticle is a thin waxy waterproof layer that we find on the outside of leaves sometimes stems but never roots speaking of Leaves we moved on to the mesophyll layer which is the middle layer of the leaf it is where we find the specialized mesophyll Palisade cells and the mesophyll spongy cells speaking of that packaging tissue we looked at also mentioning the ground tissues parenchyma collenchyma and sclerenchyma again if you'd like more detail on that go and watch my plant tissues video we then moved on to Regions or areas that you find in stems and roots and that one region we spoke about a lot was the cortex the cortex is this packaging layer it is often right underneath the epidermal layer when we see this in stems and Roots please don't think cortex core that's not what it means we did just now mention xylem and phloem so I'm not going to go over those again the cambium remember cambium is a word to describe that very unique kind of tissue that can grow into almost anything cambium does fall under a non-permanent or semi-permanent tissue it often allows for lateral growth and plants getting wider along with that we also spoke about the pericycle and the pericycle is closely related to the cambium the pericycle is not a tissue but rather a region it's very similar to the cortex it is an area or a layer a name we give a layer speaking of layers we also have the endodermis which is the inner skin like layer and that we find in Roots it has a very important job of funneling water from the outside of the root to the core of the root and it does this through the casparian strip which is this waterproof waxy layer right in the middle of the root and it funnels water into xylem which we'll get to in more detail at a later video we also looked at root hairs and stomata which were specialized epidermal cells that allowed substances into and out of a plant now if you like this video make sure you give it a thumbs up and I will see you all again soon bye [Music]