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Current time:0:00Total duration:11:00

Intro to vascular tissues (xylem & phloem)

Video transcript

when plants appear on the land for the very first time these plants were extremely tiny like Mars and algae and for a few million years there were no plans on our planet which could grow taller than few inches but why well turns out growing tall has some challenges however with time plants slowly started evolving and eventually they were able to overcome those challenges and as you know today we can have tall plants plants which can grow into trees trees which can grow hundreds of meters tall and so the question we want to try and answer in this video is what are the challenges that the early plants faced because of which they couldn't grow tall and how did they overcome them so the biggest challenge that these early plants faced was a lack of a transport system what's a transport system and why do they need them well let's take an example and understand this for example consider my house plant in order for this plan to stay alive all the parts of it require food and water and minerals so that they can grow but where are they available now you might know that most of the water and the minerals are available in the soil so the soil contains water and it has minerals in it minerals and the plants have roots which can absorb these water and minerals so great but what about the rest of the part of the plants like the leaves how do they get that water well can you see the plants need to transport that water from the roots all the way to the leaves and all the other parts so can you see that a transport system is needed to transport this water and it's dissolved minerals up right similarly think about food how do plants get their food you might know that they photosynthesize they use the energy of the Sun to create their own food and most of this photosynthesis happens in the leaves okay so let's say let's say some of the food is synthesized in these leaves consider these are food ok these are basically sugars let's call them as food as of now now what about the parts of the plants that cannot photosynthesize for example roots can photosynthesize because they're under the ground they're not exposed to sunlight there may be certain growing parts of the plan which might require this food because they cannot photosynthesize maybe there are some leaves somewhere which are an absolute shade and because of which they are not able to photosynthesize so again what to do we need a transport system the food needs to get transported to the different parts so again the food needs to get transported down maybe to the roots sometimes it might have to get transferred up to some other parts so can you see a transport system is necessary without which these plants cannot survive and the ordinary plants didn't have a transport system and therefore they were very tiny the thing is if you are very tiny then this transportation happens just by diffusion diffusion is a process in which stuff moves from a region of high concentration to lower concentration so if it's very tiny these food particles these sugars can easily move into the different parts of the plant they can easily diffuse into it similarly the water can easily diffuse to all the different parts of the plant but as the plants get taller then diffusion becomes super slow and it almost becomes impossible to transport it just by diffusion this is where specialized transport system is needed and so eventually plants evolved these transport system today they're called as vascular tissues so the transport system evolved are called vascular tissues and the word vascular vascular means vessels vessels I like to think of them as pipes so you can think of them as pie it's a piping system through which they can move the food and water or along their body and what do these vascular tissues look like well just like the name suggests they look like pipes so pipes which start from the roots so let me show you the roots and so pipes that start from the roots and go all the way to each and every leaves I've not shown it for all the leaves but it goes to each and every leaves but wait you may be thinking how can we use one pipe to transport both food and water won't they get mixed up well to make sure they don't get mixed up we have to separate piping systems one for water and one for food and we give them names so the piping system that we use for water is called xylem so xylem transports water and the dissolved minerals okay when we say water or it already has dissolved minerals and for food we have another tissue called phloem oops it's flow yum and this one transfers transports food mostly sugars but it can also transport other things like hormones Minow acid it's another step but mostly mostly food and the way I like to remember this I remember watching this in some YouTube video I like to remember this as for for food and for phloem so food phloem fur fur and another reason why they have to be separate is because if you look at water the water transport is only one direction up can you see why because all the water and minerals are present in the roots right so we just have a transport up to all the leaves but the food transport has to be in both directions sometimes you would want the food to go up maybe to the growing areas of the plants sometimes you want the food to go down in the roots that's where the storage organs are right so you see food needs to be transport in both directions and therefore xylem is only one way transport up and form well that is 'we transport so it makes perfect sense to have two separate vascular tissues altogether and so this white line I have drawn don't think of this as a single pipe but imagine it's a bundle of a lot of xylem pipes and a lot of form pipes together in fact let me show you a little better if I were to zoom in on to this and if we could see inside these are the xylem and the phloem bundles again each one has a lot of xylem and phloem teachers inside and if you could see from the top if you could have a microscopic view of this right then it would look somewhat like this this is what you would see in a microscope okay and what you see over here these are the vascular tissues again let me zoom in even further so if we zoom in one of these parts you can see a lot of lot of round things over here these are the xylem let me just mark them these are round things that you're seeing over here these are the xylem tissues they are the pipes that are coming out of the screen okay think of it that way they are the one that transport water these over here and then you can see pipes over here as well you can see small small round things over here as well they are much thinner than xylem these are the phloem okay between you have other cells but these are the forum and so you can see a lot of xylem and a lot of phloem are bundled together along with some other supporting cells as well and that bundle is what I've drawn over here so the single thing that I've drawn over here is both lots of xylem x' and lots of form together and these pipes this start from the roots and they end all the way into the leaves so let me show you a sumed inversion of the leaf all right you may have seen a leaf like this the veins that you see in the leaves are actually the xylem and the phloem these are the vascular tissues and then you can see they branch off and to becoming smaller and smaller let me zoom in even further and you can see them branching off like a network of roads connecting different different parts of the city right this way they make sure our maximum number of cells are able to get the food and water how the transport system in plants work isn't that amazing and now that they have developed the vascular tissues nothing can stop them from growing tall growing into trees to grow hundreds of meters tall because of which we have forests and jungles and everything but finally you might have another question how do these transport systems even work I mean in tall trees how are they able to get that water from the ground all the way to the top is there some kind of a pump and I guess that's where things get even more interesting no they don't have a pump yet they use some clever mechanism to get their job done and we look at these mechanisms in great detail in the future videos okay but one of the things about not having a pump is that this whole system becomes very slow so plants because they don't have a pump they have slow transport system but you know what that's fine for them the plants are saying it's okay we don't have a rush we don't have to go anywhere they have pretty low energy demands and so they can easily survive with a very slow transport system they don't need a pump unlike animals who have very high energy demands and animals do need a pump that's why we have a heart heart is our pump but plants and trees they don't need that and as I said we will look at how these things work without a pump in the future videos anyways that's it for this video so let's quickly summarize what did we learn in the video we saw that plants have developed a piping system to transport food and water which we call the vascular tissues we have two different ones one to transport water unidirectional transport called xylem and want to transport food in both directions bi-directional called phloem and the way I like to remember this is for for food for for phloem and since they don't have a heart their transport system is pretty slow but that's fine because their energy demands are pretty low as they don't have to go anywhere they're pretty much still and I would like to end by asking you to wonder about one thing can you imagine how different our world would be without vascular tissues