 Hi, I'm Tori Clark and I'm a postdoctoral research scientist at the Australian National University and in my research I'm looking at ways to improve photosynthesis so that we can grow more food to feed the world. And today I'm going to talk a little bit about how plants specialise the cells that they have so that they can become plants that can do photosynthesis and grow in different environments. So plants start from an embryo which is inside a seed and this is a single cell and within that single cell we already start to see some differentiation so the different ends of the cells start specialising and growing in different ways so that as that cell divides we get a differentiation in the tissues and in plants two main tissue types are derived from that initial cell and we call these meristems implants and these are kind of similar to stem cells in animals so a meristem is a region of cells which can then further differentiate into lots of different cell types and plants are quite interesting because they're a little bit different to animals in animals stem cell is quite determinate so if you want to become a heart cell you would start with a stem cell of a heart and that stem cell can then only produce stem cell produce functional heart cells conversely if you wanted to be a liver cell you would start with a liver stem cell but in plants they actually have this great flexibility in the cell types they can produce from their meristems so from the chute meristem they can produce a range of different tissue types that produce the above ground parts of plants so these are the stems and the leaves and even the reproductive organs such as flowers and from the root meristem it can produce all of the root tissue that's below the ground so how does a plant cell know what sort of cell to become if there's such a variation in what's going on and this is another way that plant cells are quite different to animal cells plant cells are really responsive to the environment around them so it's about actually the location of those cells and what's going on around what environmental signals they're getting from the atmosphere sunlight gases but also signals from the neighbouring cells around them and those signals actually switch on different gene expression patterns within the cells so you can think of gene expression patterns as basically like turning on and off functions within the cell so if a plant was growing and it needed some structural support it would want to produce cells that can be really strong and so one of the ways plants do this is to have cells that produce a secondary cell wall for extra strength and so the genes that control that would get switched on in those cells and the signals would get integrated from the environment around it so we would know that it needs to produce those different signals so from a single cell in an embryo plants can then differentiate right through to produce all these different cell types which then go on to create the different tissues and organs that make the functional plant.