 In this video we are going to talk about tissues, oops not the tissue which you use after being scolded by your parents, we are going to talk about tissues of the living world. So here are few plant cells, happy plant cells okay. Now they will hold hands together okay and will perform a specific function. Let's say they all formed the outer layer of the leaf. So here they will create a protective layer for the leaf right that is their function. So the definition of tissues goes like this. These are group of cells that share similar structure and they work together to carry out a specific function. Now we have touched upon this concept already in our previous videos right when we discussed animal tissues. So this video we will talk specifically about the tissues of the plant kingdom. Now animals we know are constantly on the move right they are moving either in search of food or shelter or maybe a potential mate. But that's not the case for plants they have rather a very laid back stationary kind of life. But if you look closely you will notice that even with stationary life plants have to work really hard to thrive. They have this urge to grow tall, they have to prepare their own food and then they have to take water from the soil they have to absorb it through their roots so it's really hard work right. So as the needs of both plants and animals are very different their tissues are very different and it's fascinating to see how nature has tailored the tissues to meet the needs of both these living organisms. Now when scientists closely examined the tissues the different tissues found in plants they found that the tissues in plants are comparatively very simple and they could be fundamentally divided into two different types. They found tissues that had cells that were actively dividing and then there were tissues whose cells were not dividing at all. They called them dividing tissues or meristematic tissue or non-dividing tissues or permanent tissues. Okay here I would like to share an interesting fact with you. In any plant the tissue that is found in abundance are these non-dividing or permanent tissue and not the dividing ones. Interesting right? Just think about it. Meristematic tissue has dividing cells which means it will increase in number as the plant continues to grow. On the flip side if a tissue consists of non-dividing cells it won't undergo division so naturally you would expect that the number of non-dividing cells or permanent tissue would be relatively small in a plant right but in reality it's actually the opposite of that. So what goes on? What do you think? Well here is the explanation. The permanent tissues are formed from the meristematic tissue itself. Yes, every time the cells of the meristematic tissue divides it will divide into two right and one of those cells will remain meristematic meaning it will retain its ability to divide further while the other cell the newly formed cell will head off to become a part of the permanent tissue and the process continues. So every time a meristematic cell divide it will give rise to a cell that will be a part of the permanent tissue and that is how the permanent tissue are more in number than the meristematic tissue in any plant. Now what just happened? The meristematic tissue it gave rise to special kind of tissues right? A permanent tissue. Now there are various types of permanent tissue some responsible for water transport, some for say transport of food okay there are various kinds of permanent tissue and here the meristematic tissue it converted into a type of permanent tissue into a special type of permanent tissue and this process of formation of specialized tissues from meristematic tissue is called differentiation. Now you will come across this term a number of time in biology every time there is this specialization happening it will be termed as differentiation okay. Now we will talk in detail about the function and roles of this differentiated tissue or the permanent tissue in our future video but in this video we will limit our discussion only to the meristematic tissue and let us begin with the cells that makes up the meristematic tissue. So as you can see here are few cells that are stuck together forming a tissue and since these cells have the property to actively divide they also have special characteristics right and the first among them is that they have very thin cell wall which helps them to rapidly divide right next they have very dense cytoplasm because their metabolic rate is so high they need a lot of ingredients to keep dividing okay that's why they have very dense cytoplasm along with a very prominent nuclei and they don't have any vacuole usually we get to see large vacuoles in plant cell right but these cells they don't have vacuole can you tell why well vacuoles are mostly meant for storing stuff and these cells are like hey come on we are doing enough we are dividing rapidly don't give us this extra responsibility of storing stuff okay we don't want to do that while the cells of the differentiated tissues or the permanent tissues in our future video we will see that they do have vacuoles in them so these were some properties of the cells of meristematic tissue now given their incredible property to divide these tissues are found in the growing regions of the plant unlike animals whose growth is pretty uniform the growth and plants are limited only to certain areas I would like you to pause the video and think of those areas where growth take place in a plant okay so the first answer would obviously be the shoot tip right because the plant will grow tall so the meristematic tissue will be found in the tip of the shoot but then we cannot have a healthy tall plant without deep rooted roots right so the roots should also equally grow below the ground and to grow they will need meristematic tissue so even in the root tips it will be present here as well so in all the tips there will be meristematic tissue now the plant also grows in diameter right so the meristematic tissue will also be present in these parts the lateral parts of the plant where else well you must have noticed new buds or branches arising from this nodal areas right so we have meristematic tissues there as well so as you can see these meristematic tissues are not just limited to the tips of roots and shoots but they are present at various locations in the plant body right and based on their location in the plant body they are named accordingly the one present at the apex of the root and shoot are called apical meristem the one which are present in the lateral part are called lateral meristem and the one present in the nodal areas are called intercalary meristem now here I have a very interesting thing to show you I found a video where we could actually see the division of meristematic tissue so here we have a shoot tip okay the darker or the reddish black areas are the meristematic tissues okay now as I play the video keep a close eye onto this reddish dark areas what did you observe let's play it again so as you see this shoot tip growing these darker or reddish area are getting restricted to these corners here and this corners as you may already guess gives rise to those intercalary meristem later in the plant body right because these are where the leaves and new branches will grow from and again the red colored part is located on the tip of the shoot which helps them to keep growing tall so this is how meristematic tissue gets distributed in different body parts of the plant that's why if you ever try to cut off the tip of the shoot of any plant what would happen after few days you will see that a new shoot is arising from this intercalary meristematic area from the nodes right because that is where the meristematic tissue is you will very prominently observe them in grasses as well so here is a grass blade this is where it is attached to the shoot and the meristematic tissue will be here right so after being grazed upon let's say the cattle chewed off the top part or the tip of this grass blade what happens then the grass will grow back tall again right but this time you won't see the pointed tip of the grass blade why because the cell division and development is growing in this intercalary meristematic area and not at the tip interesting right now let's talk about lateral meristem that increases the diameter or the width or the girth of the plant body especially the wooden woody plants and when you see the cross section of a big trunk of a woody tree you will see rings like this and these are formed by the division of these literal meristem these are called annual rings and we can find out the age of a plant by calculating these annual rings well how they are formed and how to calculate the age of a plant is out of the scope of our syllabus but it's again an interesting topic to read about so the lateral meristem it increases the width or the diameter of the plant so this is how the meristematic tissues are strategically placed at different location in a plant body so that they continue to grow throughout their life