Transcript

ATOM Society Introduction

Good evening everyone and welcome to this month's edition of ATOM live streaming, and welcome to our one-year anniversary of streaming our ATOM talks live by the internet right into your living rooms, your bedrooms, your bathroom. I don't know where you're watching at the moment. A year ago today was my talk and the first one that we tried out using this little platform, steam yard and we're still going and I’m so glad that you're still here with us although hopefully it won't be much longer, and hopefully we'll be able to see all your things so soon as well rather than just mine.

So, I'm really excited about this evening's talk. I had a chat with Andrew the other the other day about what he was going to talk to you guys about and it’s really quite interesting. A little bit different to ones we normally have but before we get on to that just a few little bits of admin. So as I said we're hoping that we'll be able to start having talks in person soon and obviously as soon as we know when that's going to happen and what form that's going to take we will let you know the committee is meeting very soon to discuss it and we'll be meeting regularly until we can figure out what we're doing.

A reminder please if you haven't already to please get in touch if you would like to be a volunteer for the ATOM Festival, and again the committee for the festival have not decided fully what form the festival will take. So you may not be needed to volunteer but if you are available and willing please do get in touch either to the ATOM society secretary account or to Susan directly if you have her contact details. Before we move on to the talk then.

It is time for our lovely science snippets section. Alfonso is normally very good at providing these and unfortunately, he is not here this evening as he is celebrating his birthday, I believe so I’m hoping you guys can provide some in the comments. The one thing that I saw was some fun naming of animals. It's always a great source of amusement when a new species is discovered, and the scientist gets to name the animal.

So far this month I’ve seen that there has been a new species of cricket was identified and it was named after the New Zealand prime minister Jacinda Ardern. There was also a rare snail species discovered and named after tennis player Novak Djokovic. I think this is definitely the peak of anyone's career when you get a small invertebrate named after you. Definitely what I’m hoping to achieve. So, James is waving at me so I think he has a snippet so I will bring him in. Are you just waving at me?

I was just waving at you because I like raving at you but no, I’ve got a couple of snippets for tonight. The first one is really more of an expression of disappointment and combined with surprise. I've been reading an article in this week's New Scientist by a biologist whose job is to look at the photographs taken from the perseverance rover on mars and select the rocks which she thinks they're worth saving. So, she then instructs the rover to pick them up with this robot arm and store them in some sort of container and they stay there for 10 years. In 10 years’ time apparently another space mission is going to go to mars and retrieve these samples and bring them back to Earth for analysis, and the question she was talking about was whether or not you'll be able to tell whether there's been life on Mars from what the rover will discover. What I can do is do some chemical analysis and look at these things but what it doesn't have is a microscope so you can't look for little fossil things on these rocks. Now I don't know. I looked up the Amazon website this morning and you can buy a microscope for 30 pounds and I have no idea what NASA’s funds are like, but for 30 quid I thought at least they could put a microscope on there we might be able to see these little fossils. Before 10 years are up and I’m hopeful I'm going to be around in 10 years’ time but there are no guarantees of course, that's my first snippet disappointment and surprise.

The second one is what's going to do with space, you may have heard over many years now there's been some rumours or some speculation that there's a ninth planet out beyond the orbits of Uranus and Neptune. It's been given the provisional name of Vulcan nobody's ever seen it but we've seen evidence of something out there, perturbations in the orbits of these outer planets and some movements among the rocks and the Kuiper belt. But nobody's seen it and the calculations based on what's been seen in the gravitational effects have been that it'll be about 10 times the mass of the Earth so it's quite a big thing but nobody has seen it and they feel they ought to have seen it by now. It's big enough to have been showing up in telescopes but now there's a wonderful theory that it isn't a planet at all, it's a small black hole a primal formed at the time where the universe was formed initially.

So, it's not a collapsed star, not a massive black hole in the centre of a galaxy but a primordial black hole formed when the universe was first created in the big bang, and its size would be about the size of a grapefruit. Let's just imagine that a mass 10 times the mass of the Earth the size of a grapefruit so no wonder they haven't seen it but maybe it is sitting out there in our solar system, but the article did reassure me that it's not heading this way so I guess we're safe for a while from being sucked into this thing anyway fascinating stuff all of it, isn't it?

OK, thank you Danielle. Thank you very much. That was really interesting. You should probably get onto the finance guys at NASA to make sure that they are appropriating their funds properly next time so they can fit a microscope on the rover, and while you're at it I think Tony can be on their brand naming committee because he came up here with Roxanne box so thank you for that Tony, and Leonardo’s got in touch with along similar lines to me saying that there was a new dancing spider discovered in Australia and this was named after nemo the clownfish because his face is orange and white. So, apparently the researchers there couldn't come up with an existing person to name the spider after and instead chose an animated character. Thank you very much Leonardo. If anyone else has any tickets please feel free to pop them in the comments and I’ll try and bring them up at the end of the talk.

Main talk

So now on to the main event. Our speaker this evening is Dr Andrew Galloway, and I’m really interested to hear about his talk. Andrew Galloway is a plant scientist and he's interested in the science behind plants. He originally studied at a horticultural college which was in Yorkshire, and before he went on to gain a horticultural degree at university, at which point he realised two things - that he was still interested in the science behind plants but he was not interested in being outside in the mud and the wet, so he moved over a little bit and that's when he did his master's degree in needs and then went on to do his PhD, specialising in roots which is something that he was able to develop further in his postdoc before moving over to Norway - right up at the top he assures me, the very top of Norway - where he was studying tropical plants of course of all things to be studying in the arctic circle. But I’m sure that he will go through some of that with you this evening. So, Andrew, welcome and over to you.

Well, thank you for that kind introduction. So, my talk today is going to be split into three sections. The first section will be about the basics of roots and the basics of plants and why plants are important. Then I’m going to move into more of my research area which is on plant mucilage and where it comes from, how to collect, and what it's made of and what its purpose is. Then I'm going to sort of move into the more practical applications of the soil, so detecting the mucilage in the soil and the importance of aggregation, soil erosion and I’m going to conclude on this really interesting finding that is the Wood Wide Web is.

I am absolutely mad about plants, like everyone knows or anyone that knows me knows that I love plants. Plants are absolutely important for life on Earth. They are the main basis of a lot of building materials such as timber, and they form a lot of materials that we wear such as cotton. Also form the main basis of, well the vast majority of medicines on Earth and they produce a lot of different stimulants such as tea and coffee. They produce a large quantity of the Earth's oxygen and they are natural carbon sequesters - they've taken the carbon from the atmosphere and they integrate them into their leaf and into their structure. So, they are natural carbon sequesters and of course they produce a large, large, large variety of food, as well as animal feed. It's been shown if you take a few minutes or a few hours just to walk in the countryside or forest to be surrounded by plants, it's beneficial for your mental health and this image here at the top was taken when I went to the Eden Project, and that certainly helped my mental health during lockdown.

A recent NASA study has also shown that certain house plants such as the Peace Lily (image down here), which can actually take in toxins from the air such as formaldehyde and actually integrate it into their structures so it is slightly beneficial to have as a houseplant. Of course, there's a large trend at the moment for taking in-house plants, I know from personal experience. I've got about 80 houseplants and I’m not willing to stop. And just a final image here, plants just want to grow. As soon as you put a little leaf cutting of this Devil’s Ivy plant in water; within two days you'll have some root growth. So, plants are amazing - now moving on to my research area.

So, my research area involved the plant root soil interaction, the interface known as the Rhizosheath rhizo being ancient Greek for root and the sheath being the actual interaction area. Now this is quite a busy diagram but I just want to sort of highlight the fact that plant roots don't just take, they actually have a complex interaction with the soil. So as many of you might know, roots do take water and nutrients from the soil and hold the plant into position, but they also have a complex interaction

with the soil microflora. So, for instance you have mycorrhizal fungi that some horticulturists actually use via special pellets formed of these fungi. You put them into the bottom of a hole where you want to put your plants and it enhances its growth. So, you can see from the interaction here you also have this mucilage, this thick sugar layer that's been released. You also have a regular sloughing off of cells so as the root penetrates through the soil. The bursting of these cells known as lysis, releases this mucilage which is what my specific area is. This helps the roots to grow further down and acts as a lubricant and of course you have competition within the plant so different routes competing for resources, and other plants as well.

You also have a parasitic interaction with the microflora. So, it's a whole complex interaction - plants just don't take water they actually secrete virtually everything that is within the cell. So, this is the rhizosheath in a nice neat diagram but in real life the rhizosheath is (here). So, you have the root - this is wheat that's been grown in specialist soil that has been dried and it's been taken out, and any soil that remains is the actual rhizosheath (here). This is where the root secures the soil particles mechanically so it holds on as well as the mucilage, which sticks to it. And this is where the water and nutrients are taking up and this is just what it looks like in real life.

Now if you use more powerful microscopes, you can see the rhizosheath in more detail. Here we have an image - so you see the root which goes along here and then you have these small little lateral roots so these are holding on to the soil and then on the surface. These very, very tiny things are root hairs which actually take up the water. So, the vast majority of the surface area is there to absorb water and in this image anything that's really sort of black and dark is the actual organic matter in the soil, and then here you can see a bit of silica so this is a bit of sand in the soils - semi see-through. In this image we actually stained the major components of this mucilage to see where it was and actually where you can see.

There's just blackness here, where you can actually see where the roots are growing and you can see vast quantities of this green stuff wrapping around all the particles holding onto them, and some of it's a bit blurry. This is actually secretion so here we have the roots holding on the soil and secreting so you can actually see this complex interaction. So, now I’m going to move on to my actual research area.

So that was a broad introduction; taking a step back plant mucilage this sticky viscous polysaccharide matrix which we'll explain later. It isn't just a root phenomenon, it's secreted among a variety of the sort of organs of plants. Here at the top, we have English ivy and most people believe that English ivy climbs onto the wall by clinging on through specialist aerial roots as it climbs. In actual fact, it secretes - through little pads – mucilage, which helps to stick onto the wall so it's like a spider-man interaction that sticks along and then it's only the older growth that comes along and uses the roots to cling on.

Then of course you've got the carnivorous plants such as Sundew that releases a vast amount of sticky mucilage which fools insects into thinking it's lovely nectar, but as soon as they land on it, they're stuck and the plant consumes them. And then some plants release mucilage from their stem. Until fairly recently it was believed to be a waste product, but in more recent times it's been shown to attract beneficial insects such as ants. The ants climb up, consume this mucilage, form a home next to the plants, and then defend the plants from any invaders or actually weeds to the little gardeners.

Of course, quite a lot of plant species release mucilage and their seeds in particular release mucilage on mass. So, this staining (here) is pectin – used in jams - this is a major component of mucilage and you can see vast quantities being released. This helps the seed to stick to the soil and helps to develop a microflora with the soils of various bacteria like our guts. It helps to secure resources for growth. Here in the middle of this is a maize root, and maize roots secrete an absolute mass of millilitres of mucilage, which is perfect for my kind of experiments. This is just an image here showing the mucilage sticky stuff coming from the cap.

And then finally we have plant parasites. So, there's various plant parasites, one of which is the Dodder, which I was working on in my last postdoc in Tromso. The dodder wraps around the host, and just before it penetrates it needs to develop a sticky pad to secure the plant in position it tightens its grip. Then a pincer-like organ, which is this here comes along bursts through the cell walls and consumes the host resources so this is just a very broad view on mucilage, but my experiments focused on root mucilage.

Taking a step back, what are sugars? There are three main types of sugar, here we have monosaccharides mono meaning one and saccharide being Latin for sugar; examples would include fructose and glucose and at the bottom you can actually see the ring here it's just one ring that's where the mono comes from. Most people actually know disaccharides ‘di’ meaning two, and at the bottom you can see two rings and the most common ones are lactose and sucrose. Sucrose being what you put in your tea or coffee. And then polysaccharides, poly meaning many. You can get many of these monosaccharides linked together which form various long strands such as starch and cellulose. When you wrap these long strands together in a rope sort of format, it gets very tough structures so you can see when you get monos put them together you build up these structures.

I'm now going to sort of explain the fact that there are different polysaccharides so at the top right you can see cellulose and this is just formed of glucose monosaccharides – many, many of them linked together to make a polysaccharide. But when you change or decorate this backbone of glucose - when you add xylose decorations for example you actually get a xyloglucan, which is a different polysaccharide with different structural properties. Then below this cellulose, if you completely change this backbone and add xylose you get a completely different polysaccharide known as xylan. The main thing to take away is that you have various different types of monosaccharides similar to beads; you put them together to get different polysaccharides and they have different structures and different uses.

Then just below these monosaccharides at the top in the middle we have pectin. Pectin as many you might know, is used as a gelling agent in jelly for instance, and this is formed of basically four super domains various different polysaccharides again you have lots of these decorations you put them together you get a different polysaccharide and below you can actually mix protein and encapsulate them in lots of different monosaccharides forming polysaccharides. It's a glycoprotein so at the bottom the sort of pink green colour represents the protein and then you have the monosaccharides in yellow and blue here, which surrounds it again forms different properties and different uses so having lots of monosaccharides put them together like beads on the chain. With this in mind you can form many different polysaccharides.

Moving into plant cell walls which is where mucilage comes from because of the polysaccharides. You can see a classic image of the leaf surface in the green here. When you zoom into the plant cell wall, you can see this commonly used diagram in the plant cell wall field. At the bottom the pinkish purple colour would be the inside the cell so this is the cell membrane, and at the top you have a very thick layer cutin which percent prevents water loss. Then everything in between are the polysaccharides. The orange layers represent various cellulose microfibrils linked together like a rope. They form a main structure here, and then the blue this forms this would be some glucan which cross links; this holds it together and then of course this would be filled in like a cement with pectin. Then you have various other polysaccharides holding up the structure, making it flexible. This is just a very simple diagram although it looks very busy and various plants come with various different cell wall matrices. But this just shows the basic format of a plant cell wall.

You can think of the plant cell wall as reinforced concrete so the polysaccharides would be represented by the crosslinking of these metal struts and the xyloglucan would cross link them and then you would fill it in with pectin. This you can think of is the plant cell wall. So now we've explored where plant polysaccharides come from, the plant cell wall, how do you collect these polysaccharides from soil?

Well, the most logical answer is you collect them from a liquid medium rather than the soil itself because it's very messy and soil is very, very complicated. Here I developed a hydroponic system to specially collect mucilage. Just down here we have a nine-litre bucket filled with liquid media, and then we have an air compressor that continuously adds in air to the liquid to prevent it from going stale. Then you get nice lovely growth. This is just the above view where the plants would be put in. But how do you experiment with nine litres? Effectively you will have to use something called an ultra-filtration system. Essentially, it's a concentration method so at the top here you have the pump, this big block that pumps the water through the system and then the silver bar that's where the cut-off point is. There's a specific filter which aims to collect polysaccharides and anything above a certain cut-off point. Then you recirculate the liquid so that it goes round and round in the system. Anything lower than the polysaccharide, and the average polysaccharide density goes through the waste and that's essentially water and anything that's not so interesting. It cycles through the system and at the end you get from 9 litres to 100 millilitres which is more manageable.

Then you basically have to process the sample, which I won't get into too much detail. A long series of different methods are used, so essentially, we'll collect the polysaccharides, and you go from 9 litres to a nice fluffy white candy floss-like material and it's this isolated mucilage which I can analyse. This is what the hydroponic system looks like in real life. It doesn't look so fancy I’m afraid but it's very effective. So those are the 9 litre buckets, air compressor tubes and then you've got the plants. I grew the plants for two weeks, and this is two weeks of wheat growth. An interesting observation is that when grown in hydroponics plant roots more than double their size, and it's believed this is just because there's no friction and its easy access of nutrients. This is perfect again for my experiments.

Once you have collected these polysaccharides, how do you analyse them? How do you know what's in this sample? In my lab, in Leeds we used antibody probes. What are antibodies? Well at the moment they’re very topical with COVID. Antibodies are the proteins that seek out antigens or foreign bodies that are in the body. They’re a part of the immune system that seeks out these foreign invaders and it sticks to the surface of them. Then the immune system seeks out these antibody markers and then forms a defence.

That was a very broad explanation, but essentially you can use them as probes because they are quite specific, so for example if you eject a mouse or various other animals with xyloglucan let's say the mouse will then have an immune reaction. Then you can collect the antibodies just at the bottom here. Then you have to purify them of course and then you can use these to detect various polysaccharides, so the antigen could be cellulose, it could be whatever polysaccharide you want or protein.

The main sort of probes that I experimented with used to detect and analyse these polysaccharides were antibody based because we use them with the method, ELISA or Enzyme-Linked Immunosorbent Assay. How does this work? Essentially you get a well, represented here and then you have an absorbent lining which binds to literally anything in the sample. You then add your sample which will hopefully have the antigen or the polysaccharide that you want to detect, and you then add the antibody that is specific to the antigen of this polysaccharide. Then you add a secondary antibody which contains a special enzyme, which converts the liquid from clear to a blue colour. Then you fire various lights and detect the absorbance. You can see if your antigen, the polysaccharide you're looking for, is present. Essentially the bluer is the more the higher the detection rate of the antigen is. It's not quantifiable but qualitative i.e., you can estimate how much of your antigen is present, not exact levels.

The first experiment that I did was to detect what was there, so I did a widescreen antibody test. At the top here we have various crop species. We have wheat, barley and maize which are all grasses and then we have pea tomato and rapeseed which are all eudicotyledons. The reason why I chose these types of plants is they have a very different plant cell wall matrix and they have various different polysaccharides within the cell walls - it would be a nice comparison. Then along the top here we have the antigens, so with various pectic polysaccharides we have AGPs which I showed before – that are formed of arabinogalactan protein.

Then we have extension which is another protein mixed with polysaccharide xylene and the glucan, and as you can see where we have colours so this is a heatmap there is a presence of that polysaccharide - just here we have LM6. This is pectin in barley. There's a signal here so this shows that this arabinan and galactan, pectic polysaccharides are present. We can also detect AGP in the grasses, as well as extensin and xyloglucan.

Then when we move over, we can see there's quite a strong signal from the AGPs, and then some pectin, and still some xyloglucan and xylan. Now the interesting finding here is that I have a xyloglucan and it's strange because grass is traditional grasses don't really have a lot of xyloglucan in their cell wall, yet we're detecting it being released. This sort of spiked my interest and what's happening here. You would expect quite a high signal or a higher detection in the eudicotyledons so you've got tomato and rapeseed, which has a lot of xyloglucan in their cell wall but they don't seem to want to give it up. This is a very interesting finding.

I took this further by trying to quantify how much xyloglucan was being released - this is just showing the detection, whereas, this chart shows the actual amount as I look at being released. Just at the side we have the amount being released and then at the bottom we have various plant species to compare. Again, we have the grasses, wheat maize and barley, they have quite high relative amounts compared to their cell wall. It's very interesting and yet pea, tomato, rapeseed and Arabidopsis, this is basically a weed that grows anywhere but it's a model species so it's very good to compare so they have slightly lower rates compared to wheat let's say, which are highly developed crops bred by humans.

I want to then move on to very primitive, early plants so these are liverworts. These are very small plants; they are colonisers to the early land and there are just various species such as Marchantia here and they're releasing a lot of xyloglucan. Xyloglucan is in their cell walls but they're releasing a lot more than wheat. This again is a very interesting finding. Then I explored the accumulative rates. I choose wheat and Marchantia which are polar opposite plants. You can see that the xyloglucan is increasing in a similar pattern. It's very interesting that these two plants from very different lineages are releasing xyloglucan if you wind back the clock.

I've highlighted Luminaria which was also done in analysis, this is another liverwort. Triticum if you can see there - that's wheat - if you turn back the time there's about 400 million years that separates them. This is astonishing that these two plants from very different fields, and very different lineages are releasing xyloglucan. This is just an image of a Marchantia (this is a liverwort). This just shows how radically different it is from wheat, here in green. This is the thalamus so this is a very primitive leaf of sorts. This is where it photosynthesizes, and this would be very small so one millimeter just here.

Then these were the white arrow which is pointing to the rhizoids. This is a primitive form of root; this was grown on a very absorbent layer. Then you can screen with antibodies. This antibody, LM25 binds to xyloglucan so it's a very good probe for xyloglucan. You can see the darker sort of black colour that's revealing the presence of xyloglucan. You can see they present the tips of these primitive roots, which are released on xyloglucan. It's a very similar sort of format to what we see in the literature for higher plants, the crops and again when we repeat this for wheat, it's a slightly different method because it's so big. We grow the wheat on a highly absorbent layer and it detects through the LM25 probe for xyloglucan. As you can see on this print, in purple here, anything that is sort of blurry, that's what's actively being released. It's diffused, it's moving across the absorbent layer, and anything that's very sharp in focus is actually just the roots in printing on this absorbent layer.

You can see masses of xyloglucan being released along the whole root system, particularly more at the ends, the tips. Just down here where it's very diffuse, these two species form very different lineages. Again, it's fascinating that they're doing something very similar. Now I’m going to move on to soil and sort of glance on the actual purpose of releasing these polysaccharides, specifically with xyloglucan. To explore what these molecules are doing to the soil structure. So, like with my talk earlier, I’ll be stepping back for a bit. What is soil? Soil is a complex matrix; you might have heard that a spoon of soil contains millions and millions of species of bacteria fungi. It's very complex and very rich so early soils very primitive soils would be from volcanoes, for instance the volcanoes will then blast all their rock ground up rock and ash which will then fall down to form land. Over centuries, about thousands and thousands of years this rock would be grounded down into small particles via wind or by the waves from the ocean.

This grounding of rock forms the basis of soil. The reason why you see lots of arable farmland right next to volcanoes growing crops, specifically grapes, is that it's rich in potassium and phosphorus, which is absolutely key for crops. The key ingredients for soil minerals; there's groundwork, you also need organic matter such as decaying leaves and actual life such as worms, fungi, bacteria and plants, and of course you need water and gases such as oxygen. To get from the top (here), which is an image taken from a volcano in Hawaii. You've got this massive plume of rock here to get from that to a lovely farmland, which you would get a prairie, maybe in Oxfordshire it takes on average two to three thousand years to form. It's a very slow forming process.

Now that I've explained what soils is, I will move onto my experiment that I initially wanted to do was to actually detect or see if we could detect xyloglucan in soil particles. Again, I like my contrast so we have a very developed soil system to the top right, which is a priory field. Then below we have the glacier. You can see the glacier in the middle and it's retreating along and releasing a lot of ground rock, which you can see on the hills at the side. This ground rock is very similar to the sort of images that I’ve shown you. It's ground up its, very early soil compared to the mature soil to the right, and then to the right of this slide you can see that we can actually detect a fair amount of xyloglucan so just at the side here we have the amount of xyloglucan per weight of soil.

We have the pasture, which is the well-developed soil and then we have three examples of glaciers. Unfortunately, I couldn't actually take the samples which were in New Zealand and Sweden, I would like to have gone but my research fund couldn’t afford it. But you can see that the glaciers actually contain a larger amount of xyloglucan compared to the pastures. It's very interesting, it's been shown in the literature and by our collaborators that the early soils are usually colonized by the liverworts, they are initially getting their rhizoids into the rock, and then pave the way for higher plants. This is a very interesting finding. The next step, can we detect it in real life? What is this xyloglucan doing to the soil?

Using a commercial equivalent component from tamarind seed xyloglucan, which is also used in cooking. I added this to soil and I developed two different methods, well the one on the left was quite established in geography. I used these two methods to analyse the ability of xyloglucan to be water stable or forming water stable aggregates for the clumping of soil and. Then I wanted to explore how strongly xyloglucan forms these aggregates, so to the left we have wet sieving. This is where you add your soil sample to the top and then it's subjected to a torrent of water and then you have very large sieves from descending order. Then the sieves shook vigorously. Once the cycle is complete, usually for 10 minutes you then take the soil out the sieves, dry them and then weigh. Then you can show the fraction distribution of the particles of soil.

To the right we have Dry Particle Dispersion Analysis which I helped to develop. Basically, you get your sample with the xyloglucan, and you then dry it. Then you add it to a blast chamber – silver item to the top left. The chamber actually goes around the glass slide, here you can see it's circular pattern with the soil particles on the glass side. Then you add your soil sample there and then it's subjected to a sneeze of liquid nitrogen, which sounds quite pleasant but it's quite harsh to these particles. The theory is that if a particle or group of particles are strongly associated with each other, when they hit the slide, they'll stick together. If they are weakly associated with each other, they'll hit the slide, break off and fly off everywhere. They're ground up so what we're exploring here is all these aggregates, formed by xyloglucan, are water stable and are mechanically very strongly stuck together.

We have the results here, so at the bottom here you can see aggregate size and this is in micrometres squared, and then to the left of this figure you can see the no addition control - so this is nothing added to the soil sample. Then you can see the different fractions and it's nicely distributed but when you add a commercial form of xyloglucan, for instance in blue here – this is anything about a millimeter squared, the aggregate sizes are much larger and again this pushes up all the other fractions. This chart is just showing that xyloglucan forms water stable aggregates and it's quite significant the difference.

When we look at the Dry Particle Dispersion Analysis, which is a bit more vigorous, again we have the no addition control in red and you can see a nice distribution, where you've got some larger particles about one millimetre cubed. But when you add the xyloglucan, highlighted by the blue box the particles are much larger and they remain together. So, these two analyses show that when you add the commercial forms of xyloglucan, you actually see an increase in the aggregate sizes which are water stable and are mechanically stuck together very strongly.

When we use scanning electron microscopy, you can go into much more detail you actually can see what we are actually seeing in the charts. It's always good to have images showing what's happening. Again, we have the no addition control, where you can see lots of particles without any aggregates. I have selected a random particle so you can see. It's quite smooth in appearance, there's some very small particles sticking to this particle, but when you add this xyloglucan, you can actually notice there's a lot of clumping together of these particles, it almost looks like there's a group of asteroids. When you pick a random aggregate, you can see there's quite a large particle stuck to another, the larger particle in the middle. You can also see lots of smaller ones stuck together so it looks very clumpy, and this is the soil aggregate that we are actually seeing.

Our hypothesis at the moment is that plants release xyloglucan to stabilise and strengthen the rhizosheath, and in the literature we know that certain species of grasses can actually modify their rhizosheath, strengthen it and weaken it. During periods of drought, a strong rhizosheath actually helps maintain water uptake and nutrient uptake. We believe that this is what the plants are doing. The concentrations that you saw in my charts were about one percent per soil weight. Compared to the rhizosheath, the xyloglucan added and although that seems high, it is at the levels we’re detecting at the tips, whether it's on the. As a result, it's quite comparable.

Now I'm going to move on to the degradation of the breakdown of these aggregates and why it's an issue at the moment. Obviously, climate change is very topical, and soil erosion is also a massive problem. At the moment we're currently losing a hundred thousand kilometres squared of arable farmland every year, which is equivalent to South Korea, just disappearing and turned into a desert. These are the four key major causes of soil erosion.

One cause is the use of monocultures. At the moment farms use one variety of wheat and they grow a mass of this which is quite a problem for the soil health because you need a large genetic diversity to have various different interactions with soil, and of course the plant roots hold onto the soil. When you have one plant growing in one field of course if there's a disease in one part it'll sweep across the whole field so it lowers yields. The farmer comes along to harvest the crop whilst constantly digging up the soil - tilling it - breaking down these aggregates, and soil matter degrades. This degrades soil and over quite a period of time eventually the yield of the soil breaks down.

Deforestation reduces soil arrogates; you're pulling down the rainforest such as the Amazon in which some parts are on fire. You're breaking down these natural aggregate builders, the trees taking them down, you're growing these monocultures and it weakens the soil. Then of course using chemicals, although it can be efficient. This is a sprayer, image to the left. Farmers also use a lot of nitrogen which is good for fast growing crops you've grown fast harvest the next one moves them in but of course it reduces the plant's reliance on soil fungi. The mycorrhizae fungi, which I mentioned at the start. When plants don’t get enough nutrients they don't want interaction so they get rid of it or they don't interact with fungi. This lack of interaction weakens the soil microflora and of course when you're pulling plants up every year the microflora doesn't sustain itself.

Moving on to the big one, extreme weather. When there's a flood, soil well washes away and it gets destroyed. Additionally, there's not much oxygen for life to exist and then with extreme periods of droughts, soil aggregates degrade. The plants die as well as the soil’s microflora die. So, what are the solutions? Obviously, the answers to these problems are very easy but trying to implement these changes are very difficult. Of course, we can reforest areas to prevent desertification. In the northern countries of Africa, they are grouping together to build effectively a green wall using lots of trees, and they hope it will prevent the Sahara from blowing further down into their borders and reducing their crop yields. At the moment there's still quite a lot of work to be done but there's quite a lot of success in reforesting areas.

You're taking in more carbon and putting it into the ground. It's good for the environment and it also increases soil aggregates which holds on to the soil. With the problem of monocultures, you can actually have polycultures so you can have a variety of crops growing in the field, and you have crop rotation which a lot of gardeners and allotment growers actually use. This helps to keep aggregates, having permanent plants the trees various fruits which are perennial that also helps to stabilise the aggregates and increases yields.

We want to encourage plants to have more interaction with the microflora such as the mycorrhizae fungi. We could use less nitrates which of course leach into waters causing algal blooms but this is quite difficult because the plant will grow more slowly slightly reducing yields. Perhaps in the future there could be a development on organic soil conditioner, sort of like the mycorrhizae fungi pellets that you get for a horticulturist but on a larger scale. There's so much research to be looked into. The final solution is to reduce emissions which is a lot easier said than done. Reducing emissions and taking carbon out of the atmosphere reduces chances of extreme weather, through drought and fires. Doom and gloom a little bit there but there’s hope.

I’m sort of coming to the end of my talk where I’d like to come up with my own sort of snippet of research which is the Wood Wide web, and this is a fascinating discovery it was theorised in the 60s and it's only until about the 90s that people have really got into more detail of how this system works. The Wood Wide Web, its name is derived from so the World Wide Web is formed of fungi and specifically, mycorrhizae fungi. There are two types of fungi which I’ll briefly go over. These types refer to the way they grow, so you've got ectomycorrhizal fungus which represents 10 percentage of fungi plant interactions, and basically these fungi form a netting over the surface of the roots and it takes in nutrients and water gives it to the plant in exchange for carbon usually through glucose.

The majority of plant fungi interactions are through the arbuscular mycorrhizae fungi, and they penetrate through the cell wall of the root; it grows straight through and forms these arbuscules (highlighted here in red). These form almost like a marketplace so the fungi takes in the water various nutrients and gives it to the plant through these arbuscules and then the plant in exchange for this service gives a bit of carbon. The basic difference is one penetrates roots and the other doesn't.

This all connects into a very complex network called the Wood Wide Web and this web connects whole ecosystems such as a forest. If you can imagine going to your local forest walking around and trying to imagine all these trees, the plants or most trees plants and fungi because not all plants have these connections. I've got some artwork together and put a pretend forest together and at the bottom we have all the roots so we have roots from the trees and various lands we have grasses and smaller plants growing in. Then you have in black squiggles that is the fungi hyphae, which are very similar to roots but for fungi and this hyphae forms a massively complicated network that connects to various plants, essentially shuttling resources. It's been shown that if one plant, let's say to the right here needs a resource i.e., some carbon the tree over to the left to pass the required carbon.

The fungi can actually shuttle the resources to the plant if needed or if there's a plant in shade and it's not getting much carbon it fully shuttles carbon. At the moment scientists don't really know how the fungi regulates this so much but it's a very interesting finding. How do scientists know that these plants are connected? There are various experiments that can be done but basically you use radio-carbon. Your radio-target carbon so at the top you have carbon dioxide (here), you put it in this bag and then you surround a couple of leaves. You leave it for a few hours and then hopefully the tree has fixed this carbon into glucose and then it shuttles this glucose into the tree's roots where it would normally store it or use it for various growth. When it gets to the roots the fungi then take that for payment for water nutrients exchange. This glucose could be traced from this plant to the fungi and shuttled along in this vivid pink colour to the tree in need or another part of the fungi network.

Then you can actually detect this radiocarbon label from various plants now if the plant didn't have this fungi interaction this radio-labelled carbon could only protect be detected in the trees or represented in red here, or the roots it wouldn't be spread across the forest or in specific areas. The Wood Wide Web can be seen as sort of a natural welfare system, where plants can enter this system willingly, they can reject the system when they have enough nutrients, they don't really need it. You also have parasitic interactions to consider, it's very complicated but I think it's a very fascinating idea that whole rainforests are connected, and it's kilometres squared that this fungi interaction occurs.

I’m now coming to the end of my talk and I would like to present some take home messages. Plant roots don't just take from the soil they actually have a complex interaction. They do take water in nutrients but they actually release carbon, they slip off cells to lubricate the roots to go through the soil, they have microfloras like that of our guts, they have fungi interaction. Then the parasitic interaction so plants secrete mucilage that help them to create a micro-environment. This rhizosheath has been shown that certain grasses can actually regulate this and it creates a more favourable environment so plants can help maintain water nutrient uptake particularly during periods of drought. Soil erosion which is the degradation the breakdown of these aggregates, is a major concern because we are losing a hundred thousand kilometres squared

every year.

Nice thing to finish on, the Wood Wide Web connects whole ecosystems it's an into a very complex interaction between fungi and plants. Two entirely different pillars of life coming together and working together and of course plants are awesome. Get excited about plants! I would like to sort of summarise by thanking everyone who was involved in this research. So, when I did my actual masters, PhD and first post doc talk I was in Leeds, under the guidance of Paul Knox. Who is an inspirational PI I have to have. Then Susan Marcus who was the lab manager and without her help wouldn't really have gotten a lot done. Then my collaborators at the University of Leeds. And yes, that is us in the graveyard, it's the Bronte's Graveyard so it's not just any graveyard. Then I would like to thank my other research group, the Kirsten Krause Lab at the University of Tromso in Norway, which is right at the top of Norway in the arctic circle. I would like to thank her for her help with my soil analysis, and then all my research partners there and then below - it just looked like we were on the TV show but we were not.

Just at the bottom, the University of Leeds, the BBSRC, and the TRF Foundation for funding my work. I'd like to thank ATOM for inviting me to talk about plants, which is my favourite subject. So, thank you very much for listening. Do any of you have any questions? And of course, I've included my social media at the bottom for advertisement purposes.

Thank you very much, that was really interesting, I don't think I’ve ever really thought about the content of soil quite so much and also my new favourite phrase is a ‘sneeze of liquid nitrogen’. So, yes if anyone has any questions? please put them in the chat if any committee members in the green room have them, please wave. I'll bring you in to ask them.

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