Hello my dear children, namaste and welcome to the very first session of our next unit, Plant Physiology for ICSE class 10. Yes, we are getting started with the chapter Absorption by Roots and this is Ambika, your Biology Master Teacher. right here on this amazing platform of Vedantu. Well guys, talking about the amazing platform, do remember to stay subscribed to this channel Vedantu 9th and 10th English because as you know, especially now that we are coming closer and closer to its end of the academic year, it is time to be updated, to stay updated with everything that we put up on this channel.
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It's never a crime to commit a mistake because we're all humans, right? So mistakes are very, very natural, but it becomes a problem when you don't learn anything from it. Okay. So mistakes are only proof that you are trying. So trying is never a problem, right?
Just keep trying until you succeed. Yes. And today let us learn about the functions of roots.
Of course, roots. and all of these simple simple things that we have perhaps known right since our childhood need of water and minerals for plants characteristics of roots for absorbing water overview of a few phenomena helpful in absorption okay all right getting started with what we call the root system and shoot system of course icse class 10 students i know all of you know what a root system is and what a shoot system is definitely everything that's below the soil we call it the root system right and everything that is above the soil we call it the shoot system and what does it include the stem leaves flowers fruits and enclosed seeds if at all it's there within the fruit right all of those are part of the shoot system so we can basically summarize it this way root system is the underground part of a flowering plant shoot system is the portion above the ground well actually the root system would be the underground part of any plant for that matter right not just flowering plants. All right so now coming to the functions of roots. The functions of roots we all know it does a lot more than just anchoring the plant in the ground there is a lot that it can do. What all?
Of course anchoring the plant in the ground is the first and foremost function of the root system. Secondly it also helps in taking in water and minerals water and minerals dissolved in it which are all in between soil particles they can be taken up by the plant with the help of this root system thirdly to bring water and minerals up to the stems how does it help if the water is just within the roots itself right water has to be pushed to the upper parts of the plant by some mechanism only then it's becoming helpful to the plant right so with the help of xylem tissue your roots i mean your plant's roots are also able to achieve that sort of function. Then to bring prepared food from the leaves to the roots, phloem as we call it, right, because phloem tissue like xylem, xylem and phloem are basically what we call conducting tissues, right, xylem helps in water and mineral transport, phloem helps in transport of prepared food which is the end product of photosynthesis from the leaves to the different parts of the plant body. okay.
So this also needs a sort of interaction between the root system and the phloem tissues obviously and then of course in certain plants it also acts as a sort of storage area for food okay, root vegetables and all of that as we may call them, food storage can be a function in some plants. Okay now coming to why plants need water and minerals in the first place. Well there can can be a lot of reasons. First of all for photosynthesis of course water is used up in green leaves as a raw material in the synthesis of glucose the process which we call photosynthesis. How does photosynthesis work?
The plants are able to take in carbon dioxide from the atmosphere. combine it with water which is the ingredient we obtain from the soil as we have just said with the help of the root system and in the presence of sunlight and in the presence of chlorophyll which is the magical pigment in plants which gives leaves its green color the plants are able to synthesize carbohydrates especially in the form of glucose which is C6H12O6 glucose and oxygen is released as a byproduct. So there are two major functions of photosynthesis one is providing food for the plant itself and providing food for all the other organisms around the world.
Secondly, oxygen which acts as the life sustaining gas on our planet. Well we will learn more about photosynthesis in the next chapter. For the time being you just need to know why water is essential because photosynthesis is a major physiological process in plants. Water is a major ingredient of this process.
Okay next one transpiration. Transpiration. is yet another physiological process in plants just like how human beings we sweat right we call it perspiration.
Likewise plants carry out what we call transpiration which is loss of water in the vapor form right. So how exactly does this work? You will understand more about it in upcoming chapters as well but then for now just understand that a large quantity of water from a plant body does get evaporated as water vapor during transpiration.
So why is it even significant? That's the question, right? It helps in cooling the plant body, especially in hot weathers, just like sweating helps cool down our bodies.
Transpiration, which occurs as a result of this kind of systematic water transport, right? From the roots to the upper parts of the plant body and from the aerial parts of the plant, it gets lost in the vapor form through the openings, which we call stomata. So as a result of a process like this cooling of the plant body in hot weathers occurs right.
Secondly the second advantage of transpiration is to produce a sort of suction force. Well I will tell you more about this later on but then just remember that because water is getting lost from the stomata from these upper tissues of the plant body it continuously tries and creates a sort of vacuum a sort of suction force to pull in more and more water. So. from the below parts of the plant body and hence from the soil itself, from the root itself.
So this pushing up from the roots does occur but at the same time transpiration has a sort of pulling effect as a result of which a continuous column of water gets maintained in the plant body. Okay, so this is about transpiration. So we have seen photosynthesis and transpiration, how water plays a major role in these two.
Now transportation, I have told you all about the element fluid. Xylem especially is involved in transport of water and minerals, substances and water solution from the roots upward into the shoot or with the help of phloem from leaves to other parts of the plant. This is all happening with the help of a watery medium in the plant body, right.
So transportation of materials requires water. Then mechanical stiffness. Now if you have ever...
being the kind of person who has a nice garden be it a few plants in your little even if it's a balcony garden it's all right if you have a love for taking care of the plants that you are growing like watering them regularly some plants need water on a daily basis some of them need water only on a weekly basis into one right so if you are the kind of person who takes care of all that you might have observed whether or not your plants leaves are appearing hydrated or whether they are appearing drooped in and dehydrated right. So mechanical stiffness is seen in a plant when it is full of water or rather when a plant cell is turgid or full of water it appears very very healthy and mechanically stiff. This is what we mean by mechanical stiffness.
If it's dehydrated if it doesn't have enough water in it I mean the plant cells they don't have enough water in them I mean they They are obviously not turgid. They appear something like this, like drooped down and hence they do not appear stiff, right? This is what we call a healthy turgid plant. Okay, now coming to the characteristics of roots for absorbing water.
What makes roots special? What makes them eligible to absorb water? There are three major pointers for this. First of all, all roots are provided with tiny hair like structures which we call root hair okay so root hair increases the surface area okay greatly increases the surface area which is exposed to everything that's lying around the roots within the soil under the soil right so root hair greatly increases the surface area just like we lie inside our intestines they greatly increase the surface area right this way right likewise root root hair in a plant body greatly increases surface area exposed.
Secondly root hair cells if you actually observe them they have got large storage vacuoles right. They have got large vacuoles which are filled with cell sap all sorts of fluidy contents inside the cell getting filled inside the vacuole collected inside the vacuole we call it the cell sap. sap within the root hair cell has got a higher concentration than its surroundings. So what do you think it's the advantage?
Well you will understand more about it as we proceed more and more into this chapter but for now for starters just remember that when there is greater solute concentration inside a cell it means that as compared to the outside when there is greater solute concentration inside a cell there is tendency for the cell to draw in in water naturally. Okay. More and more solute concentration inside.
So less solute concentration outside. That means water naturally flows from lesser solute concentration to greater solute concentration. Okay. So hold on to that. Even if you have questions, it is alright in that point because as I said, I will be coming back later in this chapter to explain more about that.
Okay. Now point number 3, they have got, root hair cells have got thin and permeable cell walls to allow water. Permeable is something that permits or allows, right? Thin and permeable cell walls which allow water to enter inside. These are the three major characteristics of roots for absorbing water.
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There are so many phenomena. Now, we have seen what makes roots special, why are water and minerals important, all of that we have seen, right. So, now coming to the phenomena which help in absorbing.
Okay, now before I forget, talking about importance of minerals, it is also important to keep in mind that in addition to water, minerals also play a role in all these functions like photos and things. and respiration and all of that in plants because just like in the case of human beings many times iron deficiency calcium deficiency all that becomes a problem for us right likewise in a plant body if there is a deficiency or a shortage of any mineral nutrients say for example magnesium deficiency of magnesium or manganese or something like that it would lead to some kind of deficiency sufficient chlorophyll might might not be produced which means leaves might appear yellow and not green and so on. It might appear drooped down.
A lot of other deficiency symptoms can be seen in plants also. That is another importance of minerals. Okay, let us talk about the different phenomena which help in the absorption process starting with what we call imbibition.
Okay, now imbibition is a phenomenon by which living or dead plant cells absorb water by surface attraction. Now if you have ever observed if you live in a in a wet place like for example Kerala has got a lot of monsoons and there are many other parts of India I think Bengal also has a lot of monsoon like heavy monsoon, Karnataka some parts of Karnataka, Goa and all of that also. So these people might I mean other places also of course but I am just giving you examples if at all you have observed that in the monsoon or the rainy season your doors like wooden doors and windows if at all they are there at home they may appear a little jammed you may find it a little difficult to shut them completely because they seem to have grown up swollen up that's actually not growing up the cells which are part of that wood they have taken up the water of the rains and this is an example of imbibition imbibe and swelling up.
Once again read the definition it's a phenomenon by which living or dead plant cells absorb water by surface attraction. It's just falling on the surface of that cell and the plant and the cell and the plant cell dead or living plant cell is just absorbing it. This is an example of what we call call imbibition. Imbibition is very very important as far as a root hair cell is concerned because the root hair cell when it first comes in contact imagine this is a root hair okay there would be a cell in it when it first comes in contact with the water drop it would get absorbed by the process of imbibition.
So this is phenomenon 1. Next is phenomenon 2 which is diffusion. Diffusion I think everyone knows. Think about any.
example that you know about maybe dropping putting a drop of ink in a glass of water or a beaker of water you would see that within a few seconds or within a few minutes the entire solution has turned blue because the ink drop has basically diffused across that solution right that is an example of diffusion okay. Now that it is just one example around you one common example around you but diffusion can happen in any means. medium, solid, liquid, gas, anything.
So as far as plants are concerned or in general as far as the definition of diffusion is concerned we can define it as you see in this representation the free movement of water molecules from higher concentration to lower concentration during direct contact. In the example which I told you contact between the ink molecules and the water molecules. The ink is spreading across and diffusing entirely.
entirely until they become uniformly spread, right. So this is also important for various kinds of transport inside a plant body, diffusion be it gases or water or anything diffusion is very very important but in this chapter we are mainly concerned about water and mineral transport. Okay now coming to something very similar yet a little different osmosis. The phenomenon by which water molecules move from area of their higher concentration to an area of their lower concentration through a semi-permeable membrane.
That point is very very very important semi-permeable membrane. Without the word semi-permeable membrane the definition of osmosis is incomplete. Always remember this and osmosis is also different from diffusion in the sense that in osmosis we are specifically talking about water movement of water molecules from a region of their higher concentration which means wherever water molecules are higher in concentration from there to wherever water is lower in concentration okay across a semi-permeable membrane.
Now what is a semi-permeable membrane? A membrane any membrane which allows only certain substances to pass through and not everything to pass through for example our cell membrane or the plasma. membrane. It is a very good example of a semi-permeable membrane.
In all eukaryotic cells, the cell membrane is supposed to be semi-permeable in nature. So again, imbibition, diffusion, osmosis also is very very important as far as uptake of water by the roots as concerned. Now coming to yet another kind of phenomenon which is active transport.
Now active transport like the name indicates. it is very very active in the sense what it does is now in diffusion what happens is from an area of higher concentration to an area of lower concentration movement naturally occurs right this normally occurs like even if you are imagine that you are riding a bicycle along a slopey area when you are going downhill from a place at an elevated position somewhere down the slope this way You don't really have to even pedal. You will automatically move with the flow, right? That is an example of diffusion.
Say for example, you don't have to spend any extra energy there. It naturally happens. Whereas when you are riding the cycle uphill, you have to spend some extra energy, right? That is because you are going against gravity, correct? So you have to spend some extra energy.
You have to be really active. So back to... of transport also is a kind of transport in plant bodies there is active transport in all living organisms right now we are concerned about plants okay so active transport is the phenomenon wherein there is passage of substances from lower concentration to higher concentration can you imagine if that has to occur obviously it doesn't naturally occur like the uphill riding the cycle example which i told you there has to be energy expenditure very very very important Using energy from the cell. That is why it is called active.
Because active has to strike the bell to you when you are writing this in your exam. It means energy. The opposite of active transport would be passive. transport like the case of diffusion right.
Okay so I think this animation, this simple animation here also makes it very clear to you from wherever those tiny green molecules are lower in concentration from there to where they are in higher concentration it is moving but at the cost of energy. Alright so that is active transport. Now there are a couple of other terms that you have to know, turgidity and flaccidity. Now turgidity is the term used to represent the condition of a cell, of a plant cell when the plant cell is completely filled with water. Remember I told you about watering the plants?
Turgidity is when the plant cell is completely filled with water. when a plant cell accommodates maximum amount of water. Flaccidity is a little different from that. I mean very different from that. I wouldn't say completely dried up or dehydrated.
But then flaccidity is the term used when the cell content is sort of shrunken, kind of dehydrated. It loses water. There is some kind of intake.
But then there is more water which is getting lost as a result. result plant cells can become flaccid as well remember turgidity and flaccidity now why is it even important in this context you will understand more about it in our upcoming sessions okay these are the terms which i wanted to introduce you to okay so now it's time to have a quick check let's see how much of all this you have understood ready guys okay the process by which water gets evaporated as water vapor in plants is called transportation, transpiration, condensation, osmosis. Yes, very very easy.
ICSE class 10 students, certainly you must be ready with the answer by now and your time is up. Of course it's transpiration. Next question, roots absorb, dash, water only, minerals only, water and mineral nutrients, sugars.
Now I will be able to judge if you have listened to me today or if you have not. And your time is up. Of course it is going to be water and mineral nutrients.
Remember xylem plays a major role in this transport. Now concentration of cell sap in root hairs is dash, higher than the surrounding water. pay careful attention okay.
This is a little trickier than the previous couple of questions. Second option is equivalent to the surrounding water. Third is lower than the surrounding water and the fourth is dissolved in surrounding water.
Concentration of cell sap in root hairs is dash. And your time is up. The answer is higher than the surrounding water.
When I just say concentration, now not just me, in biology in general, whenever we say concentration of a solution we are talking about solute concentration in that particular solution. So remember as I told you if this is the root hair cell it has got a huge vacuole within which there is a highly concentrated cell sap. When there is a huge solute concentration inside the cell sap what happens? Naturally it draws in water by osmosis. Okay?
Yes. So this is why naturally concentration of cell sap inside the root hair cells is higher than that of the surrounding water. And now coming to the next question. Which statement is true about root hair cell walls?
Cell wall is thick and impermeable. Cell wall is thick and permeable. cell wall is thin and impermeable or the cell wall is thin and permeable.
Thick impermeable, thick permeable, thin impermeable or thin permeable. These are the options for you about root hair cell walls. Yes and your time is up.
The answer is the cell wall is thin and permeable. Remember it's the cell membrane which is semi-permeable but the cell wall is completely permeable. almost entirely permeable yes so very very well done children absolutely well done if you have got all the questions right if at all you haven't doesn't matter at all just go back watch the replay get your concepts clear and then come and attend next session okay that's what is going to help you become better in this chapter well let me remind you that you now know about the functions of roots need of water and minerals for plants characteristics of roots for absorbing water and an overview of the major phenomena helpful in absorption. What have we discussed under that?
Imbibition, diffusion, osmosis, active transport, turgidity and flaccidity. These are the major terms we have discussed under these phenomena. phenomena and now coming to the homework question name five mineral nutrients which are essential for plant growth okay any five any five mineral nutrients which are essential for plant growth right so remember to visit children the link in the description box below and the pinned comment as well and apply the coupon code amdpro because we're going to pro subscription it's not a joke certainly something that will complete your preparation for exams so children if you have enjoyed this session and found it useful click on the like button right now because that's the best way of letting us know that you want more and more sessions like these and do not hesitate to share it with any of your icse class 10 friends because i always believe sharing is caring gone are the days when you thought okay i should keep all my study materials a secret i shouldn't let my friends i shouldn't let my enemies know where i'm studying from no we always believe that sharing is caring especially when it comes to to educational material okay and stay subscribed to the channel if you haven't done that yet click on the subscribe button right now and remember stress busters are also always available so you can follow me on my official instagram page ambika underscore vedantu where in addition to a lot of educational academic posts we also put up a lot of moral story posts so that you can get quick breaks one minute or two minute breaks from your busy schedule you.
Right children? So that's about it from my side until we meet again. Stay home, stay happy, stay healthy and this is Ambika signing off.
Bye-bye.