[Music] now we'll look at briefly at Leafs a structure of leaves and how they are adapted for synthesis because they are basically photosynthesis factories a leaf is perfectly adapted to carry out this process these are the different layers of the leaf the different cells involved now on the top we got the waxy cuticle it's a waterproof barrier that covers the top of the leaf and then underneath it got the upper epidermis which is transparent those little cells you can see they do not have chloroplasts in the light goes through there and it hits the main layer the palisade mesophyll layer the meze affords means the middle layer of the leaf so the palisade cells there they are tightly packed look at them tightly packed so that no light squeezes and misses them we won't like to hit all the crop loss in those cells and the foot since this to happen Lots there the spongy layer spongy mesophyll you can see there's some chloroplasts that's our first synthesis but those cells are irregularly shaped and they are there's lots of gaps in between them those are gaps there those of what we call air spaces and those are very important to allow the gases in and around to get to all those cells because remember you need carbon dioxide and you need to get rid of o2 if you're a leaf so we need places for gases to diffuse at the bottom you've got a layer of cells called the lower epidermis and in within that lower epidermis there's a few interesting special cells they're called the guard cells and they were actually guarding a little entrance or exit to their leaf which are core which is called a stoma and locks them are called stomata the plural and there are hundreds of stomata at them underneath a leaf the tiny little pores these little holes which allow gases in and gases out it's a bit like a little mouth like we've got a mouth for breathing gases in and out going to our lungs here you've got lots these little stomata and they let the gases in and out of the leaf you've also got a vascular bundle which has got two types of cells in this item and phloem and those that sort of the transport network for the leaf in the plant we'll talk more about that in the plant transport video but that is what's going to carry the water which is needed along with the carbon oxide which comes in via the stomata for photosynthesis and also take away the product surface and take away the glucose once made to be used whatever it needs to be useful now I always like to give my class at this point a Jaffa Cake because I think it's a nice model to show the different layers of the leaf you've got that nice shiny chocolate layer on the top that's like the waxy cuticle underneath that though you've got the big main layer the orange layer the layer that pakil the punch that's just saying with your palisade layer that's where all the action happens then you've got a spongy layer just like in the leaf where lots of air holes lots of circulation for diffusion of gases if you teletraffic a over you can actually all these little tiny little holes in the bottom which a bit like stomata so it's not a great model it's a bit crude but if it helps you to remember how the structure of the leaf the different layers of the cells then that's only a good thing so as I've been saying leaves are perfectly adapted to carry out photosynthesis you've got the palisade layer which is packed with chloroplast the upper epidermis is transparent which that's light through the leaf has a big broad shape massive surface area catch more light very very thin which is a means a short diffusion distance for gases so that speeds that up lots of air spaces which helps with diffusion the leaf has all these stomata with fur gas exchange and the guard cells can actually control where those tomato open or closed and the waxy cuticle layer stops too much water being lost by evaporation all these things all these eight points mean that the leaf is perfectly adapted to carry out photosynthesis you