 The flower is not just an ornamental part of the plant. It performs an important function in angiosperms. It contains the male and female reproductive structures which produce the gametes in flowering plants. The male reproductive structure is called the stamen and the female reproductive structure is called the pistol. Let's focus on the male reproductive structure today. The stamen is made up of two parts, anther and filament. It is within this anther where pollen grains or microspores are produced. Pollen grains contain male gametes which fuse with female gametes to form the zygote. So the process by which pollen grains or microspores are formed is called microsporogenesis. Microspore refers to the pollen and genesis means creation or formation. So the creation or formation of pollen or microspore is called microspore genesis. To understand more about microspore genesis let's take a closer look at the stamen. So this is how a typical stamen of an angiosperm looks like. There is the anther and the filament. The filament is a stalk like structure that attaches the stamen to the flower. Now the anther is an oblong structure. So these oblong structures that you see here, they make up the anther and these oblong structures are called lobes. And many anthers of many angiosperms are called bilobed because they are made up of two lobes, one lobe here and another lobe here because bi means two. Now if we were to cut this anther right here in the middle, make a horizontal cut like this, we would get the transverse section of an anther and let's take a closer look at the transverse section of an anther to understand microspore genesis. So we've made a cut here and we've gotten the transverse section of an anther and it looks something like this. So this is a lobe and this is a lobe because they are bilobed anthers. And inside these bilobed anthers are structures called thika. Now thika are tubular structures. Inside the thika are pollen sacs within which the pollen grains are produced. Now each lobe has two thika. This is one thika and this is one thika of this lobe. Such anthers are also called di-thikas anthers because di also means two. Bi means two and di means two. That's just the way it is. Let me tell you that these dots that you see here these are cells that would eventually undergo meiosis to produce pollen grains. So let's take a closer look at the anther, at the transverse section of an anther. Now this transverse section of an anther has almost like a butterfly like appearance as you can see here. Now this is a thika, this is a thika, this is a thika and this is a thika. So the anther is covered by the outer layer called the epidermis. Following the epidermis is another layer of cells called the endothesium. Following the endothesium are layers of cells that make up the middle layer. Now all these three layers the epidermis the endothesium and the middle layer of a protection to the cells that would eventually develop into the pollen grains. Now the cells that would eventually develop into the pollen grains are called sporogenous cells or sporogenous tissue and they are located here at the four corners inside the anther inside each thika. These pink color cells that you see here these are the sporogenous cells and they eventually undergo meiosis to produce pollen grains. Now the sporogenous cells are immediately covered by a layer of cells called the tapetum. Now this tapetum is quite important because it provides nutrition to the growing pollen grains. The connective cells include the vascular tissues which has the xylem and phloem which provide nutrition and water to the developing anthers. Let's take a closer look at the sporogenous cells inside each thika. The pink color cells inside each of these cells are capable of developing into a pollen grain. So you have these pink color cells here and then these cells eventually undergo meiosis to produce pollen grains. This is how the process looks like. Now each of this cell inside these sporogenous tissue which is capable of undergoing meiosis to produce four microspore cells is called a microspore mother cell or MMC. So this diploid cell microspore mother cell undergoes meiosis to produce four haploid microspores and these haploid microspore are arranged in the form of a microspore tetrad because tet means four. So each microspore mother cell is capable of giving rise to four microspore cells haploid microspore cells and each of these microspore cells eventually develop into a pollen grain. Let's take a closer look at the microspore cell the haploid microspore cell. So this is how a microspore cell looks like. You have the haploid nucleus inside and it is surrounded by a layer of plasma membrane. So the plasma membrane is surrounded by two external wall layers. The internal layer which is called the intene and the external layer which is called the exene. So this intene is a continuous layer that is made up of cellulose and pectin. This exene is the external very resistant layer and this resistant layer is made up of organic matter called sporopolynen. Now the sporopolynen is quite tough and resistant material. In fact it's one of the toughest organic material on earth. This is there for an important reason and maybe can you think of why it is there? Unlike the intene the exene is not continuous. It is made up of gaps. Now these gaps are not there just randomly. They serve an important purpose. To understand why these gaps are present let's talk about what happens to this cell. So as the pollen grain develops the cell that is here undergoes mitosis the haploid cell here undergoes mitosis and forms two cells. One cell has an irregularly shaped large nucleus and it is a large cell and another cell that is formed has a smaller nucleus and little cytoplasm and it sort of floats on this larger cell. So this larger cell is known as vegetative or tube cell and this smaller cell that has a smaller nucleus and sort of floats on this larger cell is known as the generative cell. So what is the purpose of this vegetative and generative cell? To understand this let's go back to the flower. So here we are at the flower again and the pollen grain has now divided into a larger cell with an irregular nucleus called the vegetative cell and a smaller cell which with a smaller nucleus that sort of floats in this vegetative cell called the generative cell. It is usually at this two celled stage the pollen grains are released from the anther. The anther in many plants in many flowering plants bursts open at this stage and the pollen grains or the microspores are released at this stage. So once they're released into the atmosphere different pollinating agents pick up the pollen grains and drop them on this part of the pistol which is called the stigma. So the pollen grain comes and lands on the stigma part of the pistol. Now the thing here is that the female gamete or the egg cell is located all the way here inside these small lobes that you see here. This is where the egg cell is located. Somehow the male gametes have to reach from here to here. How do they do that? This is where the vegetative cell comes into the picture. The vegetative cell begins to grow and forms the long slender pollen tube. So this is the pollen tube and once this is formed the generative cell here undergoes mitosis to form two mature male gametes. So the generative cell undergoes mitosis to produce two male gametes which are haploid and these male gametes travel down the pollen tube and reach the female egg cell where they fuse and form the zygote. Now what happens after the zygote is formed is a story for another video.