Microsporogenesis process | Sexual reproduction in flowering plants | Biology | Khan Academy

0:00 a flower is the reproductive part of a plant and in this picture as you can see this flower has both the male and the female reproductive part but i have i have labeled only the male reproductive part which is called the stamen now the stamen consists of a long stalk like thing which is called a filament and it has this knob like structure on top which is called the anther and this enter is actually the fertile part of this of this male reproductive part so this fertile part produces pollens and this pollen travels all the way to the female reproductive part of the same flower or different flower and

0:45 fertilizes the egg and produces seeds and fruits so in this video we will talk about how this pollen is produced inside the anther and this formation of pollen inside the anther is called microsporogenesis where microspore means pollen and genesis means formation and also one anther do not give rise to just one pollen it gives rise to many many pollens we will see in a minute how the center does that so let's have a closer look at the anther so here we have taken a bilobed anther and thirst can be a single single lobed as well so the single lobed

1:33 anthras are called monotecus and the bilobe bilobed enter are called dithicus and the word diethicus very correctly explains the structure of the anther die means two so we can see two lobes and thickers means compartments so this anther has two compartments and the pollen and the pollen is produced inside this anther so let us have a transverse section of this pollen let's cut it this way and see what is inside the anther so with a close look into the enter you can see that the enter has this long long tube-like thing inside which is

2:20 also called as sac let me write it down sack inside which the pollens are produced this black black dots that you see these are cells which later will become pollens so the sex are called pollen sacs okay and each lobe of anther as you can see has two pollen sex this is a pollen sac number one this is number two and in another lobe this is another pollen sex so let me number it this way this is number three and this is number four so in a dieticus anther that means in a bilobe the anther

3:06 we have four pollen sex well i'm stressing so much about the number of pollen sex because because a number of questions are asked in the exam about the number of pollen sex in dieticus and monotheists and anthers now let's let's zoom in even further okay so now if we zoom in further and look at this part just this part from above it will look something like this this is the two antelope and this is the outermost layer a single sheet of cell which forms the epidermis so this is the epidermal layer and the two enthalpy this one here and the other one here is

3:52 connected with the help of a tissue which is called the connective and through this connective the vascular tissue runs uh through which the this anther gets nourishment uh anyway so this is the tissue that takes care that the two two lobe of anther is connected and apart from that beneath the epidermal layer we also have another layer which is called andutium now the epidermal layer and the endothelium along with another layer which is called the middle layer they together perform the function of protection so they protect the microspores that will be growing somewhere here so let me

4:38 quickly show you the microspores this pink pink cells that you see here are the ones that will give rise to microspores so these are not microspores yet and the yellow covering that you see beside this is the most important layer it is called the tip atom so let me write it here this is the tip beta and it has a number of function but before we talk about the functions of tipitum let's have a closer look at this part just just this tipita layer and the cells inside so i have made it outside here so this layer that you see is made up of cells these are called tipital cells and

5:25 the layer is called tapatum i have written it already so these cells this typical cells are large and it has a lot of cytoplasm and it can provide for the cells i mean provide nourishment to the cells that is that is in the inner layer and these cells the very tightly pegged cells are called sporogenous cells so let let me write it here so this here inside are called sporogen a cell and why are they called sporogenes because these cells later will become microspores but again there are so many cells inside and not all cells will will develop into a microspore some cells will

6:11 disintegrate on the way fuel will disintegrate and will be consumed by the by the cells that are in the vicinity so they will also act like a food food source for other cells and the few cells that that remain will develop into microspore or a pollen and this part uh this part is the most important part of the entire video because a lot of questions are asked from this part and also from here on this porachina cell will develop into microspores so let us quickly clear the board all right now among the few cells that are left inside inside this stupater layer let's bring one of them outside so

6:57 this one here is a cell from from this porous cell mass okay now i have called this cell microspore mother cell so we call it microspore mother cell because because they give rise to microspores right okay now before we proceed and look into what happens to this microspore mother cell let me tell you something which is common for all plants on earth a plant can either be in the gametophyte stage or it can be in the sporophytic stage and the gametophyte or we can say gametes are either male gametes and the female gametes so in order to form

7:44 gametes you may probably know already that the gametes have half the number of chromosomes or we call them haploid so gametophytic stage is always haploid while uh as these gametes fuse they form a deployed zygote and deployed zygote give rise to the rest of the plant body and that plant body is called the sporophytic stage so so that sporophyte is deployed as well the sporophyte later undergoes meiosis at one point in life and give rise to gametophyte and this gametophyte gave rise to gametes and this is a cycle that goes on uh in any

8:30 plant on earth so in this video as we are going to produce pollen and pollen being the male gamut has haploid number of chromosomes so to form haploid number of chromosome the cells or the microspore mother cell has to undergo meiosis so now our microspore mother cell is in the sporophyte stage therefore it has twice n number of chromosomes or we can say it is in the diploid stage okay now let me get rid of this okay this microspore mother cell as we just discussed will now undergo meiosis to give rise to male gametes now after meiosis we get four haploid cells

9:20 and the four haploid cells are here and these four cells are now called microspore tetrad and also this microsport tetrad can be arranged in different ways the four cells can be arranged in a number of ways so if if if it is arranged this way uh it is called tetrahedral here we can only see three cells one is behind the sphere so this is a tetrahedral arrangement this is a linear arrangement this is a iso bilateral this is same as this one and this is t-shaped there are few more shapes so so uh this tetrads or these four cells can be arranged in a

10:05 number of different ways and the most common one is this one the tetrahedral shape now this microspore tetrad is held together by a protein which is called this calories are holding all these four haploid cells together in a tetrad now all these four haploid cells develop into individual pollen particles so this four cells will give rise to four different pollen grains so to form individual pollen particles they need to be freed right so for that we need to we need to dissolve this calories and who does the dissolving so it is dissolved by an enzyme which is produced by this type atom layer remember i told you this tipidum has a

10:51 number of functions so the stapatim now uh produces an enzyme that dissolves the calories and the enzyme is called calories and calories dissolves calories so the calories layer slowly dissolves and it gives rise to four individual microspore cells and this process is called microsporogenesis the microspores are formed so are these pollen yet these these are not pollen yet there are few more changes required in this microspore so that we can call them a pollen now we will we will talk about all those

11:38 changes in a future video but uh for now uh what is what is very important and what is worth noting is that from one microspore mother cell we get four microspores and therefore from here we will get four pollens right for pollens now if in one pollen sec there are say five microspore mother cells five microspore mother cells it will give rise to how many pollens can you think can you think of an answer it gives rise to five

12:25 multiplied by four that is 20 pollens now let's say each pollen sec has five microspore mother cells so how many pollens will we get from advaithicus dithicus anther so for adithika center we need to multiply this 20 four times right because we will have 20 pollens in each of this pollen sec so 4 times 20 gives us 80 pollens so let me just write pollen here so from from one enter from

13:13 a dieticus enter we caught 80 pollens and that is the reason we see so so many pollen in just tiny tiny little flowers so this is all about microsporogenesis and after this in in the future video we will look into the changes that takes place in each of these individual cells that finally forms a proper pollen