Brian Cox School Experiments: genome editing - classroom video

[Music] in today's experiment we're looking at photosynthesis in different kinds of plants in particular plants that have adapted to live in the shade and plants that are adapted to live in the sunlight and the focus is on the different traits that those plants have the properties that allow them to thrive for example on the forest floor or in the direct sun what we're looking at is what's the difference between Sun and shade plants so you're going to need leaves um now these geranium plants um these like full sunlight but you can use things like Crest if you allow the leaves to grow big enough um shade plants there's something called a cast iron plant you can use but we used um Ivy it's very easy to get hold of or Laurel um you need your sodium hydrogen carbonate solution um you just make this up using bicarb so this is A2 mol sodium hydrogen carbon mhm how would you make that so you need 84.1 G sodium hydrogen carbonate powder and you put that into 1,000 ml 1 lit of water you get your 1 Mo solution and then you have 200 M of that 800 M of water so diluting down a fifth to get your 2 mil and once you made up a liter of it you just need about four or five drops of detergent to go into the solution um it just stops the leaf disc from sticking um and then you need your white tile so you can cut your Leaf discs out um now cutting the leaf discs you have a few different options so lots of schools will have one of these it's called a cork Bor um you can use a metal drinking straw you can hold punch as well what you want is three or four leaf discs which are as similar as possible yeah where do we go from there once you've got your discs um you would pour your sodium hydrogen carbonate the can it into be because it makes it easier for the students to pour it now this is not harmful this is baking soda diluted with water so put your finger or your thumb whatever is comfortable and you just pour if you're using a 5 cm Cube syringe just up to the 5 cm so you can either pick the leaf disc up with your finger fers or with a pair of forceps either metal or plastic whatever you have right if you just want to pop three in perfect and then put the plunger in this is the tricky part make sure your students have goggles on for this and then you you want to get rid of the air so put your finger on the top pull down you're forcing the air out of the lead leaves so making them denser and then tap this is a bit where you have to be persistent and they should look at that start the you may get the old stubborn one at the top and so you could put it in a clamp stand with a boss and a clamp um or you can just leave it on the white tole and then because we're looking at the difference between um white light and green light um just green filter paper now you just need to cut it to a size which you can wrap around the syringe and what what are the the key messages or the most important bits of science that you want them to take away comparing the sun and the shade um plants is that under the white light both of them will photosynthesize the idea is that they produce o oxygen this makes the leaf disc less dense causing it to rise green filters on the plant which just in the full Sunshine usually now it's only exposed to the green you would see a very slow rate of photosynthesis if any at all the shade plant should rise with the green filter on because it's used to having to photosynthesize using only the green light which is left by all the other plants um now when you're doing the practice IAL um and you're trying to push the air out um I would make sure my students had goggles on cuz you don't want to be squirting um sodium hydrogen carbonate solution into your eyes it's not going to hurt you but it's better to have the safety goggles [Music] on forceps would be good right okay so we've got one sinking one at the bottom and one at the top so as be were let's push the air you got no no no no air out so push up okay they're at the bottom now boys good tapping well done woo and that's what you have to be careful of [Music] so you ready to start the experiment yeah we think so so that would be turn the light on I suppose wouldn't it and start timing yeah so what what have you done to make sure this is a a fair test we've done uh three um discs of leaves so we same type of so we can take the average from all of them so we can work out what's the a average time of what how long it would take to rise you ready 3 2 1 they moving yet they're not moving yet are they no been nearly 8 minutes yeah it might take a while [Music] yeah what did you see happen we saw bubbles forming on the top and bottom and then they kept on growing and growing and just lifted it eventually for our first uranium it only took 8 minutes but for the group over there it took uh like over 20 so I don't know if it was about the power of light cuz that's important for the fair test isn't it that the light is the same brightness and the same buve and the same distance okay so so what are you doing now um we're putting the green filter onto the syringe so that there's a different color of light going onto the um leave discs and um we're going to see if that makes a difference the time it takes to rise what what do you expect will be the difference for the shade but cuz it uses less light it it will go much quicker than the geranium with the [Music] filter right boys so we've done our EXP we need to talk about what actually happened with our results I found that some leaves took uh a significant amount more time than other leaves did for us I think we might have done something wrong cuz the Laurel uh came up the quickest but then for us the geranium and uh and the ivy didn't come up plants can be temperamental so it might be that you had the syringe in the one which was quicker you might have had the syringe closer to the light um you might find that the solution the sodium hydrogen carbonate that you were using may have been slightly warmer than the previous experiment um the leaf discs may have in the syringe been facing the light more than they weren't facing the light there's all kinds of variables that if we were to repeat this experiment again um that we would need to make sure we kept the same often the leaf discs didn't rise for quite a long time but then when they did rise they Rose quite quickly did you see them moving at all cuz if you yeah so what you get is obviously whilst they're photosynthesizing they're producing that oxygen and the bubbles are beginning to collect and then finally when that leaf disc is less dens than the solution they're in then they will lift so why do you think that the plants behave differently in the different lights so maybe maybe the plants have adapted to absorb more of like say green light than the other types of light so uh ones which are more adapted to sunlight would not really focus on green light they would focus more on red and blue light to the ones which usually you can find in the shade what I would say is so they all absorb red and blue light which is so they're green but you're right that the darker green plant is absorbing more of the green light and that's what that's what you saw chlorophyll makes the plants green but did you know that there are two types of chlorophyll you have chlorophyll a which absorbs at both ends of the spectrum and you have Chlorophyll B which is a little bit not much um more in the middle so the Chlorophyll B is absorbing towards the green light a little bit more than chlorophyll a you would have more Chlorophyll B present in the Shaded ones um because they simply aren't getting the red and the blue light whereas the geranium would be getting the white light so it would be absorbing the red and the blue so it probably have more a than b yeah I I I enjoyed watching The Experiment actually it is I think it's really cool it is it it is tricky but when you you've set it up and you're sitting there watching it actually seeing Leaf discs rise as they're supposed to you see the oxygen bubbles form and you can hear the students they're all quite excited about it whose Leaf disc is rising first which one's going to get to the top first one goes up then it comes down but it's fun and it's not often photosynthesis experiments are fun so actually be able to do this and see it actually working in front of you yeah it's kind of cool what are the pitfalls um what are what are the thing the things to avoid keep a close eye on them and the syringes make sure they have their goggles on do it in the warmer months of the year and um because that is going to have a profound effect on the results yeah so it is quite it's quite sensitive to the temperature just the air temperat definely I I would be aing for the summer term if you're going to do photosynthesis practical doesn't always work out that way um but if you can do it in the summer term the photosynthesis practicals do tend to work better cuz it's just warmer now if researchers can identify the specific genes responsible for a certain trait for example as we've seen today the traits that allow plants to thrive in Shady environments then we could take those genes and put them into crops so those crops would grow all year round or in places where there is little [Music] sunlight [Music]

Channel: The Royal Society

Views: 3,100

Keywords: royal society, science, scientists, scientific policy, scientific research, science uk, science research, international, international science, science education, science policy, Professor Brian Cox, Brian Cox

Id: 7DnhPkC5Ri0

Length: 12min 3sec (723 seconds)

Published: Mon Jan 29 2024