Class 10 Biology (India)
Major plant hormones (& how to remember)
Let's learn the 5 major plant hormones and how we can remember their functions. Created by Mahesh Shenoy.
Want to join the conversation?
- Good morning sir, you told about hormones secreted by plants but can u tell me about the parts which secret them. Thank you(4 votes)
following are the parts of plants which secrete the respective hormones:
Auxin is a plant hormone produced in the stem tip that promotes cell elongation.
Cytokinins are produced in the root apical meristems (very tip of the roots) and travel upward hitching a ride with water and traveling up the stem through the xylem.
Gibberellins are produced in the plant cell's plastids, or the double membrane-bound organelles responsible for making food, and are eventually transferred to the endoplasmic reticulum of the cell, where they are modified and prepared for use.
Abscisic acid is synthesized in mature leaves and transported both to the root and throughout the shoot system, primarily via the phloem. Roots also can synthesize abscisic acid and transport the hormone into the shoot in response to water stress.
Ethylene is produced in all higher plants and is produced from methionine in essentially all tissues. Production of ethylene varies with the type of tissue, the plant species, and also the stage of development.
Hope it helps.(5 votes)
- what is difference between cytokinesis and mitosis as both result in producing daughter cells?(2 votes)
- Mitosis is the process of creating daughter cells, while cytokinesis is when the two daughter cells break apart.(2 votes)
let's study the five major plant hormones see what their functions are and more importantly see how to remember them for our exams so let's start with the first one it's called oxen now I have written that in green because that's a growth hormone things which are in green are growth hormone okay so what does aux-in do a log since main job is to cause cell elongation so when aux-in accumulates inside a cell it just makes that cell elongate longer more aux-in means more elongation so what happens because of this well if you look at a plant we usually see that oxen since it's a growth hormone is found in the growing regions of the plant the growing regions of the plant would usually be like the tip of the leaves the tip of the shoot the birds these are the growing regions and that's where aux-in is found in abundance a lot of very concentrated over there and so if it causes the cells to elongate at that point let's say it causes the cells to be long it over here what do you expect to happen well the tip of the chute will start growing taller but that's not all aux-in is also important for phototropism remember what phototropism is it's where when you shine light on a plant the plan automatically turns towards that light and of course if you need more info we've talked about tropism in great detail in previous videos okay anyways how does that happen this also is due to oxen but how does the oxen so you know what let's go back and let's zoom into a small section of the plant over here if we could see all the cells over here let's see what happens once you know aux-in comes over there so let's imagine these purple dots are oxen their job is to along its cells now if light starts falling then auxins have a habit of moving away from the light that's important all right so this is the shaded region right this is the region where there's a lot of light so auxins will usually move away from the light and that means the oxygen concentration increases on the shady side of the plant and so what happens because of that and as a result will now find that this side will elongate more these cells will start along getting more compared to this side and as a result we now find that the left side the shady side will start along getting more will start becoming longer more compared to the right side of the plant now just think about it what happens if this side along gets more in kind of see that this side starts pushing more the left side starts pushing more ore here compared to the right side and if you push more from here what happens automatically this will start bending towards the right and that's how the shoot starts bending towards the light all right how do I remember this now the technique that I'm going to use to remember all the hormones is I'm going to come up with weird stories the idea is if you have viewed stories it's always easier to remember our brains tend to remember weird things so in the spirit of that how do you remember this well aux-in has the word ox in it so I remember this weird picture of an ox which in elongated head so this picture helps me remember so every time I hear the word ox in this picture comes to my hair mind and so this elongated head helps me remember ah it causes cell elongation and the fact that it's that head that is elongated the tip that gets elongated reminds me that oxygen is more concentrated usually at the tip of the chute and this elongation is what causes the turning of the plans towards the light so to remember this you have to visualize it's not enough if you just tell yourself this story but you have to visualize this okay try this and it works okay that brings us to our next hormone to talk about next hormone here's a question we know that the aux-in will cause the chute to grow taller but what will make the stem taller right what does what makes the stem taller that brings us to the next hormone so let me zoom out over here and click on the next hormone which is called gibberellin now jibun Lin also causes the cells to elongate it's also a growth hormone as you can see it's written in green but its major role is seen in stem elongation so if here is our plant then we saw that ox it makes this part grow but gibberellins are usually concentrated over here where new leaves are formed we call that as nodes all right and so jubilant causes these cells to elongate cells over here so if these cells elongate what do you expect to happen you'll find that the distance between this will start increasing and the stem starts elongating and so that's why we usually say gibberellin is responsible for a stem elongation if a plant has less gibberellin in it it'll tend to be dwarf if it has more Gible in it it tends to be tall so today we can extract gibberellin and store it in our labs and so if there are dwarf plants we can artificially spray to berlin on it and just make it grow taller now before everyone let me tell you some other functions as well since this is a growth hormone not only does it cause stem elongation but it's also responsible for causing elongation in the fruits that we find the fruits also grow tall or basically grow long because of Jebel itself and this means that if you have let's say these seedless grapes which are great right we love it as I like it a lot but these are usually tiny so to make them bigger what we can now do is we can artificially spray gibberellin on it and as a result the grapes will become big and so you get more money for that so that's great another important function of gibberellin is seen even during germination of a seed if you want to see to germinate you need a lot of dipper Lin without it the seed will not germinate at all so once enough gibberellin accumulates over there only then the seed will start growing so this hormone is useful in various stages of growth in the plants anyways as far as our syllabus is concerned we can just remember the stem elongation part that's what it's famous for and so now comes the question how do we remember this for this I like to go back to the story of how gibberellin was even discovered turns out that in Japan a few farmers found that their rice plants were growing taller for no reason they would grow so tall and then they would just die before giving out any seeds and on further investigation they found that that was because of xsg Berlin that was added to this plant due to some fungus that got attached to anyways now how I like to remember this gibberellins connection to stem elongation is I like to remember the story and what I do is I imagine that people talk gibberish to a rice plant gibberellin has the word gibberish in it so I imagine people talking gibberish to a rice plant and the plant starts growing tall so again a weird story but I want you to visualize that every time you hear the word gee Berlin is realized uber is talking to a plant growing tall and that helps me remember that it's major function is in stem elongation okay so we saw what oxen and gee Berlin cause elongations of the stem by elongating the cell itself that's great but if you want to grow and if you want to grow new leaves and new fruits and everything then you need to be able to make new cells not just make the cells elongate so how do we make new cells out of it that brings us to the next hormone and so let me zoom out over here the next hard one we're gonna talk about is cytokinin so the major job of cytokinin is to do cell division so it takes one cell if cytokine is present over there it divides it into two so cytokinin is mostly responsible for creating new cells in a plant and so without that you cannot have new leaves you cannot have fruits basically you can't have new cells a plant will not grow okay and the word cytokinin itself comes from cell division the word saito kind of means cell and the word Keenan means division and it's also cytokinin that causes branching to happen in plants we see plants have lots of branches right to do that also you require new cells without cytokinin this would be impossible of course the plant it will not survive without cytokine itself okay so cytokines main job is cell division now how do we remember this well one way is just to remember it this way but if we forget then again I have a trick for you a weird story so when you hear the word site or the word site comes to my mind and that reminds me of eyes and Keenan well there is a word key and so that reminds me of a key so here's my story okay it's gonna be weird so I imagine a key entering my eyes it hurts my eyes like anything and but magically what happens afterward is my eyes just split into two now I know how this sounds you might be wondering what does this really work but can you really remember things like this but yes it does work okay so weird things we can remember so give this a shot right cytokine insight key cell division eye division that helps me so these were the three growth hormones that we discussed now let's talk about a hormone that actually inhibits the growth that actually prevents growth so zooming out that brings us to the next hormone called the abscisic acid this is shown in red indicating that it's not a growth promoter it's a growth inhibitor its job is to try and prevent growth from happening and its major function it again has major many functions but one of its major functions about its associated with is the wilting of leaves so people found that the leaves that fall on the ground they have a high concentration of ab6 acidic acid so maybe that's the reason why leaves get cut down it's that this particular hormone that is responsible for that now it turns out that the recent studies show that this is not the real reason why the leaves fall down it shows that a Pacific acid is not really the cause for the cutting down of the leaves okay so let me just give you a couple of major actual functions of abscisic acid one of its functions is to make sure that in the drought condition meaning when there is not much water present its main job is to ensure the stomata of the leaves stay closed remember what stomata is stomata is a small opening in the leaf that causes water loss transpiration we call that evaporation of water well during drought condition system water abscisic as it gets built up over here and it makes sure it stays shut so that it doesn't lose water so that's one of the jobs of abscisic acid another job as a growth inhibitor now can be seen in seed germination if there's a lot of up state as it found in the seeds then it will not allow it to germinate it will not allow it to grow and you might be wondering why is this important this is important because we need to make sure when the seed germinates it's in the right condition so for example when the seeds are in the desert right a lot of apps leak as it gets built up over there doesn't allow it to grow and when it starts raining then the conditions are right the rain washes the abscisic acid away and once it gets washed away then the Djiboutian can start acting on it and can start making it grow so absolutely as it is super useful as a growth inhibitor even in the earlier stages of the plant growth anyways fortunately or unfortunately our NCERT or syllabus has not picked up and so in exams you are still expected to write that the wilting of the leaves is caused by abscisic acid and so that's what we need to remember so yeah the question now is how do we remember this well one is you can look at the word abscess abscess actually means cutting down that's where the name comes from even though it's not really true but if we don't remember that then what I like to do is split this word as ABS see sick okay and now I imagine a person which has great abs who has great ABS but he's feeling super sick seasick on a board and starts throwing up but instead of puke it you know it starts throwing up leaves and that's how I can remember abscisic causes cutting down awfully use so again visualize this and you'll see you can remember the in fact I dare you to forget this now this is impossible for you to forget AB seasick welding of the leaves you cannot forget it now this now brings us to the last hormone which is called it's silent it's put in yellow because it's hard to categorize that as a growth inhibitor or a growth promoter so we're not categorized this at all the Italian is a chemical that you learn a lot about in chemistry and it's major job is in fruit ripening ethylene is a gas that gets released and it causes the cell wall to get broken down and that's what makes it softer and it also releases the stored sugar making the fruit sweet so it's a fruit ripening hormone okay now this picture might make you feel very uncomfortable because you don't usually see just one banana being ripened and that's because when abana when a fruit ripens it causes more Italian to be formed and Italian is a gas and that's why that gas gets released and it accelerates the ripening of other fruits and then they start releasing more Italians and such a chain reaction happens and that's how when you keep a fruit next to a ripe fruit it becomes it ripens faster so how do I remember this again playing with the words the word eat Ilene reminds me of eat Thai eat Thai Lin and so the story over here is I eat very spicy Thai food which actually hurts my stomach and as a result I start releasing gas and that gas starts ripening the banana I'm really sorry about this dirty example but I just couldn't come up with a better one to remember that ethylene is a gas and it's a fruit ripening hormone so there we have it we have listed the major functions of the major hormones which we see in plants great idea know how to pause the video and see if you can remember our technique and remember the functions and in the future if you like this please keep using the same visualization you have to keep visualizing it over and over again to make that memory solid