Redox: The Driver of Soil Microbial Interactions with Olivier Husson

Hi friends, this is John and this is the Regenerative Agriculture Podcast. Welcome back to the Regenerative Agriculture Podcast. In this episode, I am delighted to host Olivier Husson, who has been one of my heroes for many years, someone who I have admired at a distance. When I first began studying agronomy and plant nutrition, I became really intrigued by the implications of looking at plant electricity plants functioning as antennas, and looking at agriculture and plant function from the perspective of biophysics rather than from the perspective of biochemistry. Within this context, I was really interested in learning more about redox and soil, eh and pH. In the literature review, I was not able to find very good information, except for one source. Olivier Husson wrote papers that were a voice of clarity in a wilderness of chaos. So Olivia has written a number of papers on the importance of redox and EH as drivers of the soil microbial ecosystem and soil and plant interactions. And I'm delighted to have him here today. So, Olivier, welcome to the podcast. You have a very interesting background. Can you tell us a bit about what has brought you to this research and how you came to be working in this space?

First yes. Let me say that I'm very proud to be asked and very glad to participate. I'm a big, big fan of your work, John, so it's really, really a pleasure. I'm an agronomist, French agronomist. I've been working in the tropics for more than 25 years and one of the main crop I've been working with was rice. And rice can be grown in very different conditions. It can be grown, as most people know, with water in the field, in the paddy field, but it can also be grown as wheat, a plant aerobic crop, as any other crop. And I've been working on developing cropping system based on conservation, agriculture, regenerative agriculture, and I've been working in my early time for my PhD, especially in PADI fields where redox chemistry is really fundamental and it's very well known. So I asked myself why redox chemistry is so important in paddy field in anaerobic condition and it would not be important in a plant aerobic fields. Then I started about 10 years ago to work on this aspect and it's been quite interesting work and then we can apply this to more aerobic crops, the most crops we have usually in our systems.

Olivier there is a common perception that PH is one of the most important factors for managing soil nutrient availability. And yet I've observed many environments and many fields where the PH was not where we might have had expected it to be, but we had very good or very bad nutrient availability. That was really what led me to look at redox. What is the impact of redox on nutrient availability from the soil?

I would say probably as important as ph. Ph of course, is a key factor for nutrient solubility, but it's not the only one. And if we look only at ph, we miss about half of the picture. In fact, we really need to assess both ph and redox potential at the same time. So redox potential is a measurement of the availability of the electrons, as ph is a measurement of the availability of protons. So if we draw a graph with ph and eh, we have a much better understanding of all the nutrient solubility and all the plant nutrition we can get.

I've actually, when people have asked me that question, I've said that understanding redox and managing redox is perhaps even more important than managing soil ph. And one of the questions that comes up frequently, what is the impact of redox on nitrogen availability? Specifically.

You have both an impact of EH redox potential and ph. In fact, the main component related nitrogen availability would be the oxygen and the hydrogen. So it's, let's say it's crossing at 45 degrees between pH and redox. It's really the gain of oxygen or the loss of hydrogen that will have the most impact. So it's both, it can be read both on ph and EH axis. So when you have low EH and low ph, you will have the main form would be ammonium. And when you have I, EH and I ph, you will get mainly nitrate for the mineral forms of nitrogen.

There's a growing interest in developing microbial populations that can really suppress different pathogens in the soil profile. What is the impact of redox and ph on the soil microbial community?

So this is probably the most interesting thing. The microbial activity is very much impacted by EH and ph both. And in the other way, the microbial activity will have a huge impact on EH and ph. Microbes control or alter the EH PH of the environment to make it more profitable, more favorable for their growth, for thriving. So each species of microorganism will have a specific EH and ph zone where it will thrive. So some of them are very rather ubiquitous. That means they can grow on a rather large range of EH and ph. But many, many microorganisms have a very narrow EH PH of functioning. It's very much related to the energetic functioning and to the function they will fill in, especially for the microbes involved in the nitrogen Cycle nitrification will be at high pH, high eh, and the other way around, nitrogen fixation can be done only at very low eh.

Wow. So if nitrogen fixation can only happen at very low eh, I think the experiences that I've had and what I've observed, generally soils tend to have commercially farmed soils tend to have a high eh. They tend to be fairly oxidized. Why is that and how can we reverse it?

Oxidation in the soil is very much related to the loss of organic matter and especially to the loss to the loss of biological activity. The microbes, they breathe and through respiration they consume oxygen source, so they lower the redox potential. So in order to have balanced redox potential in your soil, you need good soil aeration and very active microbial activity. And for this the soil structure is fundamental. But all this is based on organic matter and microbial activity that will improve the soil structure. So you should not get too low redox potential in your soil, otherwise it would be asphyxia. And only plant like rice which can pump oxygen through the roots will be able to survive. But you should not have too high redox potential, otherwise the plant will lose a lot of its energy to to adjust the redox potential and the PH in the rhizosphere through pumping product from the photosynthesis to activate microbial activity that will help the plant to sustain a proper environment. So it's always a matter of you should have not too high, not too low eh, not too high, not too low ph. And for all this you need very, very good soil structure and a lot of bio biological activity and good soil organic matter content. That's the basis for having a soil where plants will be able to develop without losing too much energy to adjust this in the rhizosphere.

Olivier, you've mentioned several pieces that I want to unwrap, but in the comment that you just made, when you speak of plants losing too much energy to adjust the rhizosphere, what are the different ranges of energy that plants can contribute to soils to try to correct their environment?

So in fact all the energy in the soil is coming from the plants. So everything starts with the plants, with the photosynthesis. Everything that lowers the photosynthesis will lower the entry of energy into the system. And when the soil has not enough energy, that means has a too high redox potential, that means lack electron and a too high pH, lacking proton. The plant will need to adjust, especially just in the rhizosphere. It's a matter of sustaining proper eh PH at the cell level. It's a requirement for the functioning of the plants, sustaining homeostasis for EH&PH at the cell level. And the plant has several mechanisms to do this. Some chemical buffers, some activation of genes to make proteins to adjust in the medium term. But one of the main process to adjust this is to sustain a proper EH PH level at the rhizosphere level around the roots. And for this it will pump product from the photosynthesis to the roots. All this root excudation and it will favor some specific microorganism. It depends on what the plant is missing, is lacking. And this microorganism will adjust EH PH level, the favorable level for the plant. So if in a soil, you have well structured soil with the appropriate level of EH PH in the different aggregates in the different part of the soil, because it's not homogeneous, of course, you need gradients of energy to make them work, then the plant will spend most of its energy to grow to make more leaves. So more capacity to get energy from the sun to make more photosynthesis. And this is a win win process. Then the plants will work better and better, will feed the soil. Adjust EHPH in the soil proper level and all the photosynthesis will work better. The nutrients will be easily available for the plant. So it's really a circle of improvements. Once you get at the proper level, the opposite when you are on unbalanced level, being too high redox or too low redox, then it's a vicious circle. Too low redox will favor bacteria that works in anaerobic conditions, so that they will lower further the redox potential and will lead to asphyxia of the plants. And on the opposite, too high level will mean that the plant will need to spend most of its energy to adjust in the rhizosphere. And all the energy the plant is spending to adjust, it's not available for making new leaves. And the capacity of photosynthesis is not increasing. So it's a clear vicious circle. And at the end of this vicious circle, you have a limited amount of organic matter that comes back to the soil. And the soil being very oxidized, mineralization will be very fast, so you will lose organic matter. So it's a real vicious circle. Once you're getting too oxidized, the plant is struggling to sustain EH, pH or meiostasis. And it's spending too much energy for that and cannot do it. Every year it's getting worse and worse.

So the soil ecosystem can either be constantly degrading and becoming worse and worse. Or they can be constantly regenerating and becoming better and better based just very simply on how we are managing them. And the redox data flow profile.

Exactly. All the difficulties to start to initiate the process. When you start from a balanced environment like grasses or forest, then you have rather high carbon levels, especially active carbon, the carbon that is accessible to microbes. So you will get a rather buffered EH and PH in the soil at proper level, and the plant will spend most of its energy just producing more leaves or producing more energy. And you have circle of improvements every year. It's just getting better. You have more organic matter, more biological activity, a better soil structure, so a more buffered EH phone, so better conditions for growth and so on. Once you start to lose too much organic matter and too much biological activity, your plant will spend most of its energy trying to adjust and it cannot increase its capacity progressively. You are going to lose organic matter and it's going to get worse and worse. You will lose soil structure, which is fundamental, and it's a vicious shock. So the problem is that in most of our agricultural fields, we have lost a lot of this organic matter, we have lost a lot of this biological activity, especially we started to lose the soil structure. So we really need to recover all this. So we need to restore the soil structure to install plants that will improve the soil structure, that will feed the biology in the soil. But for this, you need your plants to grow. And when the soil is imbalanced, the nutrients can be there in the soil, but not available to the plant. So you need to make sure that the plant will get sufficient nutrition to provide efficient photosynthesis so that it can feed the soil and produce more leaves.

I have always been an advocate of using foliar applications to accelerate and jumpstart this plant photosynthesis and use the plant's photosynthetic engine to begin changing the soil profile. And if I'm understanding you correctly, then you're indicating that that could also change the redox profile of the soil as well, particularly in the rhizosphere.

Yes, totally right. It's clearly the redox profile is coming from the photosynthesis, mainly the beginning of the plant. We know how to grow plants without soil, but without the plants, the soil is just becoming a desert. It's just beginning to be sand, to lose all the clay, all the organic matter, very fast. So it's the plant that makes the soil more than the soil that makes the plants, at least in a system that works in a sustainable way. As soon as the plant is taking more nutrients and more energy from the soil than it provides to the soil, the system will not be sustainable. You will lose energy in your soil. And this will also rapidly lead to favor pests and diseases in different ways. That's another interesting aspect with adding redox to PH in the perspective is that we can better understand in which condition the different kind of pests and the kind of disease will thrive. And so we can identify EH and PH condition in which the plant will be healthy.

Olivier, I've just realized that you and I are somewhat familiar with this terminology, but we're using very different terms and different language. We speak about redox and EH and ph and reduction, oxidation. Some people speak of RH2. What, what are the meanings of all of these different terms and what does for us as producers and agronomists, what do we really need to understand about EH and pH?

So it's, it's rather simple, in fact. Ph measures the the availability of proton H. E H would be a measurement of the availability of electrons. So if you make a diagram with ph on the X axis and EH on the Y axis, you will be able to assess the different zones according to ph and eh. So low PH means a lot of proton, high proton availability, and that's acidic condition. High PH is a low availability of proton and it's alkaline or basic conditions for redox. Low EH means high electron availability because the electron is negatively charged. So low EH is related to a lot of electron, a lot of available electron. So inversely so low EH means reduced condition. It's the condition where energy is available because there's plenty of electron. Inversely high eh, high redox potential. EH stands for redox potential is related to low electron availability. So very low energy in the system. Then what's important to understand is that EH and ph are related, especially in organic chemistry. And that's finally what will really make the difference. To assess soil health and plant health would be to look at a parameter. There's different ways we can do it. We can adjust eh to ph7. We can also calculate the pe +ph, which is an equivalent. PE is the electronic potential. It's just simply calculated from eh. So in fact, it's difficult to explain this without a graphic. But in fact, P ph, if you look at it on this ph EH diagram, P ph would be what drives you towards on the top right of this diagram. So IP ph would correspond to low proton availability and low electron availability. On the other side, low P ph would be High proton availability, high electron availability. So it's really where energy is gathered, it's where you have a lot of hydrogen and where you have very few oxygen. So it's very, very energetic compounds when you have such low PE +PH. And regarding the question to RH2, RH2 is 2 times PE +PH. So it's the same kind of measurements. So broadly, the real accumulation of energy on the ph EH diagram. So with the proton on the x axis and the electron on the Y axis, the availability of energy, it's at low PE plus pH. That means on the bottom left of this diagram, and it's where photosynthesis is bringing you. It's how photosynthesis inject energy in all the system. And on the opposite, when photosynthesis is not working well, you're moving to the top right of this diagram where energy is very weak, very limited.

So if I'm understanding you correctly, then when you have photosynthesis that contributes to a reduced environment with an abundance of electrons, and this is something that I find particularly interesting, is typically in agriculture and in farming, the explanations have revolved around chemistry explanations. And I can't begin to recount the number of explanations that I have heard and read that describe ph as a measurement of hydrogen, when in reality we should look at it from a biophysics perspective and not a biochemistry perspective of looking at individual elements.

Yes, ph is not directly hydrogen. It's H, it's protons, so it's hydrogens minus electrons.

What is the connection between various minerals and their oxidation states? So we can read about the different oxidation states of, let's say, manganese or iron in the soil profile and understand that some oxidation states are very bioavailable for plants to absorb and others are not. What does this understanding of this EH and electron availability mean for trace mineral availability?

So I would say the two main elements that will have a very rapid and strong impact related to EH&PH would be iron and manganese. But in both cases they will be soluble, so available to the plants in their reduced form, which is Fe2 or Mn2. And in both cases, this Fa2 and Mn2, they are in the area on the bottom left of these diagrams when you move up to the top right. So when you move to oxidized and alkaline conditions, you will get oxide or hydroxides of iron and manganese, and these are not available to the plants. So the first element that you will make not available to the plants when you get your soil oxidized and alkalinized. Would be the iron and then the manganese. And in such cases, you can add manganese or iron to your soil. If the soil is too oxidized or too alkaline or both, the plant will not be able to get it. So the plant will have some processes trying to make it soluble in the rhizosphere. The plant will spend energy to acidify and to reduce. Both processes are correct. We can measure this in the plants that they will acidify and reduce the rhizosphere. But this will cost energy. And if your soil is globally in very, very oxidized condition, you, will not be able to get your manganese or your iron. And adding manganese or iron to the soil in such conditions will not make any improvements. It's not the quantity, the total quantity you have in your soil that is the problem. It's the form under which these elements are dominant. And the only way in such case to make it available to the plant Would be through foliar application of reduced form of iron or manganese.

We have observed this with many growers that we have worked with where we've experimented with soil applications of manganese Using manganese sulfate up to a rate of 400 pounds per acre, combined with humus and humic substances, with no increase in plant absorption because the soil was in a very oxidized form.

Yes, you can even increase the deficiency doing this, because the more the concentration you will have, the, the easiest it will flocculate, the oxide will be formed. So in some cases, you can even increase the deficiency by increasing the soil content of manganese or iron.

Wow.

It's limited increased. But the real problem is that it's not under a soluble form. And if the plant cannot make it under soluble form, it will not access to this. And it's not a matter of amount you have in the soil. It's a matter of form that will dominate. And in any case, the plant will at least spend a lot of energy to reduce the rhizosphere and to acidify the rhizosphere to get these elements. So at the best, the plant will lose a lot of energy. But in the worst situation, and it's rather, rather fast for iron at pH 4.5, if your redox potential is around 600 millivolts, which is something we can rapidly gate In a soil with no organic matter, no biological activity, Iron will not be soluble at all, and the plants will spend huge energy to make it soluble.

Many of our soils are commercially farmed soils because of the way they have been managed with cultural management practices and tillage and so forth, we find that the soils are very oxidized and we get tremendous crop responses from foliar applications of iron and manganese. Even when the soil analysis shows that you have abundant levels of iron and manganese, they are not in a form that the plants can absorb. And so I think this is a very important management tool for us to recognize is that soil applications of manganese and iron are not likely going to produce a crop response. And I believe this is one of the reasons why mainstream agriculture hasn't been able to successfully get a crop response, because they're often applying the wrong form and in the wrong manner. But Olivier, something else that you've mentioned that I've been connecting the dots on. When you speak about the presence of H and abundance of electrons in a reduced environment being a very high energy state, and oxidized materials with an abundance of oxygen being in the oxidized form, being in a low energy state, that immediately makes me think of nitrogen and the differences between ammonium NH4 and nitrate. No. 3. What is the impact on the plant of absorbing ammonium versus absorbing nitrate?

So there's plenty of impact. It seems not so important because ammonium and nitrates can be absorbed by the plants, both can be soluble and can be easily absorbed by the plant. But the first impact is that a plant that absorbs ammonium will release H in the rhizosphere to balance the charge. And inversely, plants absorbing nitrates will release. Oh, so this will strongly affect the eh, especially, sorry, the ph, but also the EH in the rhizosphere. And in consequence, it will affect the solubility of all the other elements because they are very much related to EH and ph also. So the first impact is it will impact the solubility of the other elements and the difference in ph in the rhizosphere between a plant absorbing nitrates versus ammonium can be more than 3 pH units.

Wow.

You can have a plant absorbing ammonium, the PH in the rhizosphere will be as low as 4.5. On the other side, the plant absorbing nitrates, the PH in the rhizosphere can be more than 7.5. So it's a huge difference. And it strongly impacts all the other ions, all the other elements. So in a soil that is too acidic can be good to absorb nitrates, then that it will reduce. But it's rather tricky because ph and EH naturally related, they are not independent. Naturally, oxidation leads to acidification. So when Water is losing electrons, it's getting oxidized, then it produce O2 and H. So oxidation is related to acidification. And inversely reduction is related to alkalinization. So we have to be careful every time we're discussing with this kind of ph. It's not possible to assess EH without knowing the ph. And inversely knowing the ph does not much sense in soil or in a living organism if we don't know the redox potential at the same time. So both really need to be assessed together. But coming back to the plants and what are the impact of absorbing nitrates versus ammonium is the first impact is that the plants absorbing nitrates will need to transform to reduce it into ammonium to make before making amino acids to form proteins. So this is a huge energetic cost. There's 8 electrons difference between nitrate and ammonium. So that means ammonium will have eight electrons more than nitrate. So there's a few publications on this showing that a plant absorbing nitrates instead of ammonium will increase its root respiration by 10 to 15% to absorb. Because it's another. It's another point is that roots is globally negatively charged, low redox potential, and the nitrates are negatively charged also. So there's a need to make very. It's an active absorption and it requires energy. So just the absorption of the of nitrates instead of ammonium will require energy. And some part also is transformed into ammonium in the root. So root respiration is largely increase by 10 to 15%. Most of it is for absorption and some parts for direct reduction of the nitrate into ammonium in the soil. That's a first problem. Then a second problem is that the plant needs to reduce this nitrate into ammonium. And again, it's about 15% of its energy that will be spent for this. And the last part of it is that to do this, to transform nitrate into ammonium, the plant will need a lot of water. So if there's plenty of water, it's good because the plant will absorb a lot of water. The cell will be adjacent, so the growth will be very fast. But on the other side, if water is a limiting factor, and it's quite often a limiting factor in our agricultural system, the water use efficiency can be reduced. And the worst case can be in rice, where the water use efficiency can be divided by two, it would be just 50% of plant absorbing ammonia. But if there's all this problem with nitrate, not everything is perfect with ammonium, neither because ammonium absorption will lead to release of protons. So in acidic soil, it can lead to very strong solubilization of aluminum. Then you will get aluminium toxicity. But also high ammonium content in the plants will make. It will create toxicities. It will be too reduced also for. Even for a plant. And globally, there's another cost. Ammonium is not very mobile in the soil, so the cost for prospection will increase. The plant will need to make more roots or more mycorrhiza. In any case, it will need to develop larger surfaces and longer roots, longer mycorrhiza to prospect to get sufficient ammonium because it's not mobile, when the opposite nitrate is more. More mobile, so can be found in the soil, in the water solution quite easily. The result of all this is that all the plants, when they have the choice between ammonium and nitrate, they will absorb both forms. Some plants will absorb more nitrates than ammonium, like wheat, for instance, or maize. Some plants, like rice or soybean, will absorb more ammonium than nitrate. Young plants will absorb more ammonium than nitrates and then get. When they get older, it's reversed the ratio. So there's plenty of variation between the different species, between the different age of the plants, between the different conditions. But globally, they all work better when they absorb a mixture of them. But the real difference for me is when the plants absorbs organic nitrogen, amino acids or amino sugars, because then the plant will absorb nitrogen with energy at the same time the compound first these amino acids. Globally there's no difference. The charge is neutral. So there's no imbalance in the plant that is created by ammonium or by nitrate absorption. So absorbing amino acids or amino sugar, the plant will not be imbalanced for the charges. But also we get nitrogen under directly, the amino acids form a very reduced form that they will not lose again energy to reduce the nitrates or the ammonium. After the ammonium, then the ammonium needs to be reduced also again into amino acids. So the plant will spare a lot of energy when it absorbs such a form. Of course, the cost for absorption will be a little bit higher, but the energy that the plant gets from absorbing it under this form will more than compensate for this higher cost for absorption.

Olivier, you said a number of extremely important pieces, but the two that really popped out at me are that when plants are absorbing nitrate, it can require 15% of its total photosynthetic energy just to convert nitrates to amine nitrogen and amino acids. And the water cost. If you can reduce a plant's water requirements by half, simply by making sure that it is absorbing nitrogen in the form of amino acids rather than nitrates or ammonium. That is a huge water savings that is very important for much of our climactic stressed agriculture today.

Yeah, sure. Water is quite often a limiting factor and probably will be more and more often than the case. The 50% is for water use efficiency. It's related to rice, which is a plant really with high demand on water. It's difficult to find literature for the plants. But in any case, the physiological. The chemical processes make it necessary for the plants to get more water, to transform nitrate into ammonium, to release the oxygen and to get the proton in the ammonium. The plants will take the H, release the. Oh. So there's a huge cost for water and it's difficult to assess exactly how much it's for the different plants, but obviously there's a high cost for water.

Also, I think of all the work that you have done and that I've read in the conversations we've had, the piece that perhaps excites me as much as any of this is the understanding of disease and insect susceptibility based on different EH and PH factors. Can you describe some of your work and what you've been learning in that regard?

So it's some work that has been done for, in the grey literature for more than 70 years for other aspects and plants. But I'm just taking back on this kind of work. But recently in the literature, in the scientific papers, we found that redox potential was involved in all aspects of plant physiology and all aspects of plant disease interactions. It's everywhere, it's thousands of papers. It's really amazing. This started less than 20 years ago. Twenty years ago, PH was the key factor for plant physiology, plant pathology for all these aspects. And in less than 20 years, eh has been. The redox potential has been identified or redox signal have been identified as a key element that they regulate everything in the plant. It's up to a point that we don't know what is not regulated in the plant, what is not regulated by redox signal. So we still need to understand the interaction between PH and EH in this regulation. That's probably a point we really need to work at. And we cannot find really in the literature, but globally what we see and also in plant pathology, the physiological processes are getting better and better understood. So we can identify globally the different PH and EH requirements for each main type of pathogen. Plant fungi Pathogenic fungi will develop at oxidized plant and on rather acidic ph. Necrotrophic fungi, the fungi that Kills the cells and then feed from the dead. Cells are in extremely acidic conditions and very oxidized conditions. The virus is. They will develop more in oxidized conditions but at higher ph. They need high ph to be mobile in the plant. They need higher ph to swollen and then be able to replicate the rna. But they also need high redox potential to block the signal of defense from the plant by polymerization of the molecule. That will make the. That will be the signal for the plant to try to resist to the attack of the fungi of the virus in that case. So viruses. It's really rather high ph and high EH on the other side. Pathogenic bacteria will develop at low redox potential. They have a metabolism based on a lot on sulfur on iron. So they need lower redox potential and rather alkaline conditions. Omisets that were previously identified as fungi are now recognized as different categories. They don't have ketones and they are very close from the brown algae. And these are also very close, quite rather close from the bacteria. So they will be at rather low redox potential and let's say neutral ph. So with this kind of things we can better understand why the different diseases develop in one part of the plant or another part. Why they are entered in the plant at the moment or through a certain leaf. All this fits very well with all what we know. And for insects it will be rather. Also it's rather related to this. So there are some. All these red dogs you know will. Will have two impact. They will. It's. It's a war for red dogs. They will. The plant when it's attacked by a pathogen will try to kill it through over oxidation. It has not enough energy to control the pathogen by. By reduction. So it will try to over oxidize through hydrogen peroxide mainly and at the same time. So this is localized where the pathogens is attacking. And then at the same time the plant will send a signal for shifting the metabolism to more protection of the plant. So getting a lower redox potential and lower ph. Because globally it's at low EH and low ph that the plants will be healthy. And then for the insect we can also have mechanism of resistance related to low redox potential. Most insects don't like low ph and don't like especially low redox potential. Especially when you have phenols or C vitamins. They. The digestive system cannot digest this easily. But of course it depends if the insects are feeding on the phloems. Usually the phloem is more reduced and more alkaline than the xylem or the leaf tissues aphid, for instance, that will, that are vectors of different viruses will eat in the phloem. They are sucking insects eating in the phloem. So it's rather alkaline conditions and they will prefer this kind of plants. Especially when the phloem is not as reduced as it's supposed to be, especially when the photosynthesis is not working well. For the insects that are eating the plants, the biting, chewing, different ways of controlling would be through the resistance of the cell walls. But first of all it will be the accumulation of secondary metabolites that are very reduced that would be in the vacuoles. And when the insect is biting this and chewing this, it will get unpalatable food for this insect. It will not be able to digest this well. So the insect will not be attracted by such plants that have a high secondary metabolite content. So there's plenty of research field also related to this and all this. The interactions between the insects and the different diseases. Also fascinating research area at the moment. And the good thing in this approach through redox potential, in addition to ph, is that it provides a very elegant, very relatively simple mechanism for unifying all the mechanism and understanding the interactions between the soil, the climate, the nutrition of the plants, the physiology of the plants, the. The genotypic difference also. So the environment, the soil, the climate, the genotype, the different species, the different varieties, the practices, how our agricultural practices will bring the plants to one or to another area of this ph diagram, and all these in interactions with the pest and the diseases. So it's really a powerful tool to analyze all these interactions and to better understand what's happening in the different situations.

I believe that is the piece that I particularly am so excited about.