 Hi, I'm Tori Clark and I'm a post-doctoral researcher at the Australian National University and in my work I study how plants grow and specifically photosynthesis and I'm really interested in ways that we can optimise photosynthesis to make it more efficient and produce high yielding plants to feed the world. So I'm going to talk a little bit about how plants grow from cells that specialise and multiply and how those cells come together to form different structures within the plant. And so from cells we move into different tissue types and there are three main tissue types in plants and tissue types are a group of cells that form a specific function together and have a specific structure. And so if we can start with the epidermis tissue type. And so this is really similar to the skin that we have on our body. It forms the outermost layer of the plant and its function is really about protecting the internal structures of the plant. And a lot of that is about regulating the amount of water that can move across the plant surface and also gas exchange. And the epidermis of plants in structures like leaves has pores that let some water and gas exchange and they're called stomata. But the epidermis extends across all the different organs of the plant. So the plant is made up of lots of different organs and you can think of these as like the functional units of the plant. And so I've mentioned leaves already as an organ of the plant but we also have things like root structures. The root structure isn't a plant organ. And even things like the reproductive structures can be classified as organs. So things like flowers or fruit that get produced from them. And so the outermost layer of a lot of these organs is the epidermis. And then within that there's a second layer of tissue which is called the ground tissue. And so if we use the leaf organ as an example the ground tissue in a leaf is called parankyma that's the cell type. And these cells function in doing really the most important part of a plant's growth which is photosynthesis. So these parankyma cells in the ground tissue are packed full of chloroplasts. And you can see from the way they're orientated within the leaf that there's a lot of air space around them to allow gas exchange so that carbon dioxide can then get converted into the sugars. So the third tissue type within plants is the vascular tissue. And this is quite similar in its function to the vascular system in people. And so in our bodies we have a heart that pumps blood through our arteries and veins. But in the plant there's no pump system. And it's not circular like it would be in an animal. The vascular system in a plant is quite linear. And so most of the movement is sort of from one end of the plant to the other end. And there's two types of vascular tissue in plants. And you can think of these like pipes that are sort of carrying things around the plant. And the first type of vascular tissue is called xylem. And this is what carries water around the plant. And the water usually moves from the roots where the water is collected and it moves up through the stem of the plant and into the leaves where it's transpired. And the other type of vascular tissue in plants is called phloem. And this moves sugars and other organic compounds around the plant. And usually the direction of this is from the leaves which are producing the sugars through photosynthesis and moving those sugars down the stem and into the roots where they can be stored. And so really with these three tissue types what we get is different things coming together structurally. And the structure of these different types of tissues actually allows the function of the plants. And so the different organs within the plants or the leaf or the root or the flowers have different arrangements of how these three different tissue types come together. And that's to do with the function, the differing function of those different organs. And so what's really key here is that the structure of the different components, the individual cells coming together to make different tissue types really drives the function of what those parts of the plants do.