in this video we're going to take a look at the mass Transport Systems of plants so we'll explore how they transport their sugars which is known as translocation and their water through transpiration plants make their own sugars through photosynthesis but all of this photosynthesis happens in the leaves so in order to share these sugars with the rest of the plant so that they can be used energy they have to be transported somehow this process is known as translocation and it's mainly achieved by Flo cells which are arranged end to end to form long columns that we call FL tubes if you look closely though you can see that in between the adjacent cells there are lots of small pores or gaps and these pores enable the movement of celsa which is basically a liquid mixture of water and sugar this means that the sugars that were made in the leaves can be transported long distances through multiple cells once the sugars finally make it to whatever cells they're going to they can be used for two things either directly for energy or they can be stored so that they can be used for energy later and one last thing to point out is that the fla can transport substances in either direction so up or down the plant next to the flum tubes we have xylm tubes these are also made of made up of a column of cells but this time they're dead xylem cells with no ends between them so they effectively form One Long Hollow tube and they're strengthened with a material called lignan their role is to transport both water and mineral ions from The Roots up the stem to the leaves where the water can be used in photosynthesis now the weird thing about the movement of water through a plant is that the entire thing is driven by the evaporation of water from the leaves if you imagine all the water molecules as being arranged in one long chain then every time that water evaporates from the leaf out of the stamata it drags the rest of the chain up slightly pulling along another water molecule to replace it and as water is continually evaporating because remember the Tomato need to be open to let in the carbon dioxide there will be a steady stream of water flowing up the plant now the terms that you need to use when you discussing this stuff can be a bit unclear but basically we call the evaporation of water from the leaves transpiration and the chain of water molecules is known as the transpiration stream there's always going to be at least a little bit of transpiration taking place but the rate of transpiration can vary a lot and there are four main factors that influence this rate light intensity temperature air flow and humidity the bright the light intensity the more photosynthesis that can take place which means that more stamart will have to be open to let in the carbon dioxide required for photosynthesis and at the same time more water can evaporate which means a higher rate of transpiration whereas at night time when there's no photosynthesis happening because it's dark the stomas will be closed and so there's very little transpiration when it comes to temperature the warmer it is the higher the rate of transpiration because the particles of water will have more energy and so they're more likely to evaporate and diffuse out of the Stato to understand the effects of air flow and humidity it's woring a quick look at the inside of the leaf and at how water diffuses out of it because water is continually being brought up from the roots the inside of the leaf is going to have a much higher concentration of water than the outside and this provides a concentration gradient down which the water can diffuse out of the leaf so if you think about it the rate of transpiration is really going to depend on the strength of this gradient when air flow is high for example it's really windy then the water molecules that leave the leaf are quickly going to be blown away and so the concentration gradient between the inside and outside is going to be kept High increasing the rate of transpiration while with humidity which is a measure of how much water vapor is in the air more humid air will decrease the rate of transpiration because the large amount of water in the moist air will decrease the concentration gradients meaning that less water is going to diffuse out and so we have less evaporation overall if you haven't heard yet you can find all of our videos on our website Cognito dog you'll also find questions flashcards exam style questions and pass papers and we track all of your progress so that you always know what to study next so sign up for free by clicking here or browse our playlist here on YouTube