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Episode 3 | Dr. Wendy Zellner
64 Plays1 year ago
Dr. Wendy Zellner is a molecular and cellular biologist and has actively studied the role of silicon as a plant nutrient for almost 20 years. Dr. Zellner is the Owner/Lead Scientist with Zellner's Research Solutions, LLC, and a research associate professor at the University of Toledo.
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Transcript
Frog Collection Anecdote
00:00:03
Speaker
Oh.
00:00:38
Speaker
But I am curious, what's the story with Kermit back there on the wall? I actually made that myself. It's one of the yarn loop. Oh, it is. And I have a love for frogs. I used to have a frog collection with over a thousand different pieces within it when I was younger. Really? Yes, I inherited it from my aunt and no longer do I have the full collection, but I still have some of the remnants.
00:01:05
Speaker
Okay. How did that come about? Did you just naturally gravitate towards liking frogs? Well, my aunt passed away when I was young. And so she was the frog collector in the family. And green was always my favorite color. And so I was just like, oh, I'll take on this collection. And then it just grew exponentially and it got to be way too much. Oh, I see. Well, that's cool.
00:01:30
Speaker
Very cool. Well, you still like green, you like plants? Yes, I do. It was an early indication. It's my future career. Yeah, absolutely.
Introduction to 'The Ag Show' with Dr. Wendy Zellner
00:01:40
Speaker
Well, if you're joining us, you're on the Ag Show podcast, this is the place to be. And again, joining me today is my good friend, Dr. Wendy Zellner. Welcome, Wendy. Good to see you again. Always good to see you.
00:01:53
Speaker
Good to see you too, Johan. Thank you for having me today. Yeah, yeah. Well, thank you. I always enjoy our conversations and everybody that I talk to just...
Professional Relationship with Dr. Zellner
00:02:06
Speaker
They love learning about silicon and you and I, we always have a good time chatting about it. And I know we've discussed it on many occasions, some recorded, some not. Gosh, how long have we known each other? I'm thinking almost 10 years, but it might not, it might be more like eight, but it's pretty close. It's pretty close to 10, yes. I can't remember if it was 2014 in Columbus. I think so.
00:02:32
Speaker
about then. Yeah, it's kind of what I was thinking. Yeah, yeah.
Dr. Zellner's Expertise in Plant Science
00:02:38
Speaker
Well, let's for those that don't know you, if you wouldn't mind share a little bit about your background and and what who you are and what you do.
00:02:48
Speaker
Okay. I'm Wendy Zellner. I am from Northwest Ohio, born and raised. My background is in cellular and molecular biology. I always had a love for science and my parents both thought that I would become a doctor. And I did, but I became a doctor looking at plants and plant diseases versus human diseases.
00:03:12
Speaker
which I absolutely love. So I really got started as a graduate student looking into nutrition and disease where I had an opportunity to work. We had funding from USDA to look at silicon and boron and really that's when my passion for silicon came because we found a lot of what we were seeing as we were beginning the research contradicted what was being published in the literature and so
00:03:39
Speaker
From then I went on to work with USDA for a four-year postdoc, went back to the university, and now I am embarking on an independent kind of an education outreach, consulting, and research
00:03:54
Speaker
opportunity where I'm just working with growers, with industry leaders, and very heavily with manufacturers and distributors in the silicon egg sector to really understand and help elevate silicon to be recognized as a beneficial and an essential nutrient for plant health here in the U.S.
00:04:17
Speaker
Very cool.
Role of Silicon and Boron in Plants
00:04:18
Speaker
You touched upon something that I'll expand upon real quick. You mentioned silicon and boron. What's the connection between those two? Well, other than we're still learning a lot about them, they go to similar areas within the plant. We know that they're within the cell wall, important for floral development and other different things. They have similar
00:04:40
Speaker
characteristics elementally wise, so reaction wise, you can think of them. But that's kind of where they end their way and they do have different transport mechanisms, different responses within the plant.
00:04:57
Speaker
boron is probably is used at a much, much lower level than silicon with boron. If you put too much into the system, you can get boron toxicity. So the plant doesn't regulate it as well as it does with silicon, whereas silicon, you can't put too much in. And so silicon is probably doing something that's very, very fundamental, but is heavily regulated by the plant. So there
00:05:22
Speaker
They have a lot of similarities, but definitely very, very different nutrients there.
00:05:29
Speaker
there was just something about silicon that really captured your interest probably because there wasn't a lot of research limited research limited knowledge very novel at the time was there anything else that i mean what was it about silicon wow okay i want to focus on this yep we were actually working with um the lower foliar accumulators so not the hyper accumulators like the rice and the grain species
00:05:53
Speaker
But we were looking at Arabidopsis to start out with, and Arabidopsis only takes up about a thousand parts per million silicon compared to, so that's a 0.1% compared to your rice and your grains, which is at anywhere from 1 to 10% SI in the leaves. And we were seeing beneficial responses and a lot of the literature
00:06:14
Speaker
at that time was saying that dicots like Arabidopsis and like a lot of the other plants didn't really need silicon and they excluded it not like the grains and so there wasn't really a need to look into these plant species when we thought about silicon nutrition and that is completely opposite of what we were finding. Specifically looking at nutrition and viral infections at that time but then we expanded into bacterial infections
00:06:40
Speaker
And there's a lot of evidence that's been published on fungal infections as well. So from a biotic and an abiotic stance, we were seeing very similar responses in these dicot species.
Misconceptions about Silicon in Plants
00:06:54
Speaker
And that's really where just my passion to understand why and to look into that. That's where my inquisitive nature kind of took me. Gotcha. You touched upon accumulators and I was having a conversation with someone the other day
00:07:12
Speaker
Someone involved in the conversation was asking about silicon and is it necessary? And the person sharing the story with me said they started going on about accumulators, non-accumulators, metacumulators, and that depending on what your crop you're dealing with, you don't need to add silicon because it's not an accumulator, et cetera, et cetera. But I think that used to be what everyone thought, right? That's not the case anymore. So for example,
00:07:40
Speaker
expand upon that because I think you understand what I'm saying and there might be some misunderstanding of the relevance and importance of silicon in plants strictly based on maybe how much you find in the tissue if you do a tissue sample. Correct. And you're absolutely correct. We really didn't understand silicon and we really don't to the degree that we understand other nutrients.
00:08:07
Speaker
But at the time when they came up with those designations, this is when they had first tried to describe what a plant nutrient was. And so silicon was kind of just this oddball nutrient that was out there. And so they were calling the accumulators plants that took up
00:08:24
Speaker
1% or higher. So this would be in the range of nitrogen, carbon, oxygen level of nutrients. And those that accumulated lower, they were saying were non-accumulators, just simply because they didn't accumulate as much as a grass species. These studies
Silicon Uptake in Plant Species
00:08:41
Speaker
were done
00:08:41
Speaker
in the 1800s and early 1900s, where they had a really small subset of different plant species. So it was a biased view on how silicon was distributed throughout angiosperms. And when we started collecting more data, what we're starting to see if we look at silicon concentrations in plants across all plant species, so our dicots and our monocots,
00:09:08
Speaker
Most of the plants take up silicon to the same level as the macronutrients. So we're talking similar to sulfur, magnesium, calcium. And then we have those that hyper accumulate that are taking up as much as nitrogen and some dicots, especially some of the fluoroculture species will even have levels similar to the carbon. So they're taking up really, really high amounts.
00:09:31
Speaker
But then the plants that I was studying that they were talking as low accumulator species, when we look at their nutrient concentration, there's still about 500 to 900 parts per million silicon in the leaves. This is higher than iron and manganese. So they're still accumulating, and they're accumulating at a higher concentration than what we kind of think of our micronutrients. So they are kind of in that sweet spot between a micro and a macronutrients in those
00:10:00
Speaker
what used to be called lower accumulators. So that's really what we're trying to educate with and what I've really been pushing for the last few years is getting rid of the high and the low or intermediate excluder nomenclature and start talking about silicon in the concentration and in the context as a plant nutrient. So when we think of our
00:10:24
Speaker
different species are cucurbits are going to be macro accumulators taking up 1000 to 5000 parts per million and most of the dicots actually and most of the angiosperms fall within that 1 to 5000 parts per million. You do get a few that hyper accumulate that are going to take up higher amounts and like I said you do have some of them that take up those lower amounts
00:10:46
Speaker
But when we look at the beneficial response across the board, whether they're taking up 100 parts per million or 10,000 or 100,000 parts per million, they all, when they're deprived of silicon and it's given back to them, show that beneficial response.
Impact of Agriculture on Soil Silicon Levels
00:11:03
Speaker
That's why I do say all plants are silicon accumulators. You just need to be aware of how much silicon is lacking and how much silicon they need to make sure that they are meeting their requirement for growth. Okay, so let's say we're in soil and crop rotations, etc. It sounds to me, though,
00:11:31
Speaker
Unless you're cycling plant biomass into the soil or adding silicon, it sounds like maybe a lot of systems are silicon deficient, right? Are farmers unknowingly mining silicon out of their soils and those systems are essentially
00:11:51
Speaker
deficient of silicon? So a lot of work Brenda Tabana at LSU has been looking to try and come up with how we can detect silicon deficient soils. So obviously the parent material that's present within the soil, soil types, all those are going to play a factor into the silicon availability. So silicon is the second most abundant element in the soil or in our lithosphere.
00:12:18
Speaker
It needs, though, to be broken down into salicylic acid, which is the available form. And the concentration that's actually in the soil solution of that is quite low. So when we start putting some of these components back to the soil, even if it has a high amount of silicon to start with, they're still seeing beneficial responses, especially when we get into
00:12:42
Speaker
the grains and some of those hyper accumulating species. And it's because they really do have a strong draw out of that system. So in the soil profile, it's still really, really, it's a very complex story. And we're still learning about how it works and how it becomes available. But you can think of it just like a highly weathered soil. We're putting nutrients back into the soil to replenish what we're pulling out. And with the heavy
00:13:12
Speaker
agriculture and the heavy growing and the crop rotations that we've been doing. Also with the heavy feeding of other fertilizer, we don't have as much microbial action taking place within the rhizosphere. And so that is limiting likely the amount of available silicon that's being there. And so yes, when we get into these cropping systems where we haven't been putting the plant residue back or other forms of silicon that we might not even realize that we're doing, we really do see deficient
00:13:42
Speaker
soils throughout the U.S. and they are seeing quite wonderful improvements to yield and crop quality and stress management when they start using these types of fertilizers in a soil type production. Okay, and I'm going to kind of keep with this flow if we start with the soil. So silicon is relatively, its solubility is low.
00:14:10
Speaker
natural weathering, of course. Throughout some of the research I've done over the past couple of years, I've come across many solubilizing beneficial microbes. I'm sure they play a part in this as well, correct? Correct, yes. Of making silicon in an available form. I know you deal with this too.
00:14:35
Speaker
I think technically we might be splitting hairs, but it's really important to understand the nomenclature. Here, a lot of people will say silica, which is technically silicon dioxide, SiO2. That's not what plants that are taking up. You've mentioned the available form is monosyllic acid, so how do we go from
00:14:54
Speaker
in the soil silica, and I also want to touch on how growers can determine how much they have in their soil to begin with. So help them kind of walk through that. It's, solubility is low. How does it go from unavailable to available to then taking up by the plant and how do farmers determine a base level?
Mechanisms of Silicon Movement in Plants
00:15:13
Speaker
So even silica will break down and dissolve into the water. So a lot of the silicon that's in a soil profile can be bound in an amorphous form. So this, instead of being the highly crystalline, like a quartz or thinking of a diamond where it's that clear and really nice lattice structure,
00:15:36
Speaker
These more amorphous forms are just easier or even you can think of it almost like a gel in some of the material that's there. And so with that, when you have water and when you have the microbes in there, it can break it down and release that into the soil profile. And with the soil solution, you're looking at maybe upwards of 60
00:16:03
Speaker
to 70 parts per million silicon is about the max that you see there. But typically, across soil, and I, again, I should always have my notes with me because I mess up these values. But really, you see even lower than that. So even though max saturation of salicic acid in water is up at that 75, usually it's anywhere from .2 to about 25 parts per million within different soil types on how much salicic acid is available.
00:16:32
Speaker
but that doesn't mean that it doesn't have a pool of silicon to pull from. And so it's going to maintain an equilibrium. And depending on the microbes, the roots that you have, there's again, a lot of organisms that are competing for that silicic acid pool. So that's going to keep it at kind of that lower, lower levels. I don't know if that really,
00:17:01
Speaker
So the silicone there, right, depending on the form, it can be very available or it can be tied up just like we see with other nutrients. And there's a lot of factors just like we think of with other nutrients that are gonna play a role in the availability within a soil profile. And even available monosyllic acid in the soil, silicone is vital to every living cell
00:17:31
Speaker
on the planet. So not only is the plant, I guess what I'm getting at is competition. Microbes are going to be competing for that silicon as well, correct? Or anything, even earthworms, your more macro biology versus your microbiology, correct?
00:17:51
Speaker
Correct, yes, yep. And that's why when we look at levels that are within the ocean are even more depleted and silicon is really one of the elements within marine life that is a limiting factor for some of those microorganisms as well. Okay, so we've got a pool of monosyllic acid. It's around the roots.
Silicon Transport Within Plants
00:18:18
Speaker
From there,
00:18:20
Speaker
help us understand plant uptake and now we're gonna get in, it's traveling from the soil, now it's moving towards the plant, it's uptake, how does it take it up and what are its benefits in the plants, which I know are several, but I wanna, where I'm kinda going, this is clarifying what we know in the literature and then kinda what's accepted on, say, a product label.
00:18:47
Speaker
OK, so with plant uptake, we do know of two transporters that are not specific for silicon, but have the ability to move silicon through their pores. So these are just you can think of them like doors or windows in the membrane that allow the silicon to move in. And again, we do see it as moving in as silicic acid.
00:19:13
Speaker
And so in the roots, the first transporter that we kind of think of when we think of the movement of silicon in is the passive transporter, which is an aquaporin.
00:19:28
Speaker
even though it's called an aqua corn, it doesn't allow for water to move in, but it does allow for some different solutes, silicon being one of them. And so the silicon will move through this pore just down its concentration gradient. So if you have a high amount in the soil, you'll have silicon move into the root system. Then we know when it gets to the endodermal barrier, so this is where
00:19:53
Speaker
within the roots. It kind of forces these nutrients to move in through the cell so it can regulate transport. And for that, the pore that has been studied is referred to as LSI2 for low silicon and rice 2. It's also
00:20:10
Speaker
a conserved arsenic bee-like transporter, which was first identified in bacterial species. And so what this transporter is important for is the efflux or the movement of arsenic from inside a bacterial cell to the outside. So this allows for protection against arsenic toxicity. What's interesting, if you look at silicon and arsenic, where they're sitting on the periodic table, they're neighbors, so they do have a lot of similar
00:20:40
Speaker
chemical characteristics. So this is an actual active transporter that can take silicon and move it from areas of low concentration to high concentration. So in species like rice and cannabis, this is how they're able to get such a high concentration of silicon moving up into the plant is they have this active pumping of the silicon in. So even though you might have a low amount in the profile, they're going to pump it to higher concentrations within the internal part of the roots.
00:21:09
Speaker
then it gets loaded into the xylem and it moves similar to a lot of the other nutrients that we think of xylem movement like our calcium, magnesium, all those different nutrients and it will then
00:21:23
Speaker
move and be distributed throughout the plant depending on where some of these other transporters are that allow it to be offloaded from the xylem. So again, we see these aquaporins in species like rice and our grains and grasses. They actually at the node, they believe this is where the trafficking of silicon then can be moved to where it needs to go. So again, all of these pores or
00:21:53
Speaker
doors and windows in the membrane.
00:21:56
Speaker
It's all specific for plants and it's moving it specifically to where the plant needs silicon at that time of growth. So it is a highly regulated system. And this is just looking at really the aqua porn is the best described in the best studied. We haven't looked much more into that arsenic D like other than we know the poor has the ability to move it. We can see where it's localized in some of these plant species.
00:22:23
Speaker
and its expression changes with silicon, but how it's regulated when it goes into the plasma membrane, when it gets pulled out, we really don't know. And then in other species like mammals, they're seeing some of these phosphate transporters have the ability to transport silicon as well. And again, looking at the periodic table, silicon is neighbors with phosphate and arsenic, carbon.
00:22:50
Speaker
germanium, all those. So they do have similar chemical characteristics depending on what form it is, how it's interacting with other complexes. And so even though we just know about these two transporters and how it's moving, there is a lot more that we need to learn about how it's actually being shuffled around, how it's being used. When it gets into the cell, what is it doing? Is it in the cytoplasm? We do know it can get into the vacuole.
00:23:18
Speaker
with grass species, we know with the specialized silica cells, it moves into the epidermal cells, but then it gets deposited between the cell wall and actually the plasma membrane. So there are a lot of these nuances that we know, but the one thing we really don't know, why? Why is it doing this? What is its function there?
Effectiveness of Foliar Silicon Applications
00:23:40
Speaker
We have a lot of theories, we have a lot of ideas, but we really, it's an open-ended question right now.
00:23:46
Speaker
come up with a lot of plausible and what you feel are logical ideas of what it's doing there. But at this point in time, we really, we don't know what that is. But the important thing is, as I'm kind of backtracking, when we're talking about the movement in the xylem and it getting up into the plant tissue and the leaf tissue, we really don't see high concentrations of silicon moving back in through the phloem.
00:24:11
Speaker
So when we think of once it moves up into the leaves, the literature will say that it's deposited within the leaves and it has no effect. It's just going to the end of the transpiration flow and it's done there. But again, it's just a theory. Whether it's deposited, whether it's still available to move throughout the leaf tissue when it gets into there, these are all things that we really don't know yet.
00:24:37
Speaker
But one important thing, not just when we're thinking about root absorption, I apologize if I'm jumping too soon into foliar absorption, a lot of the liquid sprays that we're putting out in orchards and in other soil type growing environments, we're again applying these to the leaves, which is great for that new growing leaf, but it's not going to be able to move into the new growth
00:25:01
Speaker
after that application. And so these are some things when we think about silicon absorption and movement, it's really getting it into the root system. You're going to make sure and ensure it's getting to that new growing system, whereas foliar applications are great, just like other foliar nutrient applications. But you do need to think about, do I need to continue? How often do I need to apply to continue moving it into the xylem and getting to that new tissue?
00:25:30
Speaker
Yeah, great point. People struggle with foliar versus soil application. So I think you hit upon that. There is, much like other immobile nutrients, it's really fixed at that time of application. You're going to have to come back seven days or however long we've got that new growth.
00:25:54
Speaker
Before we move on with the second part of that question, which was additional benefits, you brought up arsenic in the similarities with silicon. And something you and I have talked about before is
00:26:07
Speaker
heavy metal toxicity in maybe certain growing environments. It seems like that might be more prevalent in maybe organic production where, say, rice holes are used because rice holes can tend to be not all. I'm not saying I'm not accusing any company of having rice holes with high arsenic, but what is the potential there for the presence of arsenic and how might silicon be beneficial?
00:26:33
Speaker
So a lot of, again, going back to rice, there's a lot of studies in rice because it is a hyper accumulator. It's kind of the oddball because it does take up so much more than the other grains. But you were going to see similar things across all plant species. So in these rice studies, what they saw is when rice is grown in the absence of silicon, it really has a strong draw for silicon. So it will take up nutrients that have similar
00:27:02
Speaker
chemical characteristics, not because it wants to, but because it's trying to fulfill that need for the silicon. So unfortunately, arsenic moves really well through the LSI-1 and LSI-2 transporter, just like silicon.
00:27:16
Speaker
What's good though is silicon outcompetes for arsenic. So silicon has a higher binding affinity to move in. So when you put silicon back into these systems, you can still grow on that soil. And usually, honestly, the arsenic levels don't tend to be toxic in these soils, but the plant will bioaccumulate them to levels that would look like you were growing them on an arsenic-contaminated soil.
00:27:45
Speaker
So that silicon is really important to outcompete for that. So now when we think about the rice halls, again, if you are getting rice halls from an area that was grown in the absence of silicon,
00:28:00
Speaker
you're not getting that silicon concentration in those rice hulls that you might think. So a lot of the literature, when we publish, and we've worked, I've worked with rice hulls with the USDA, Jonathan France, they've done a lot of studies looking at different concentrations, but they knew the source of those rice hulls, they were testing how much silicon was present within those rice hulls, so they knew there was a significant amount that they were
00:28:28
Speaker
able to supply to that growing system. When you're not dealing with a company that maybe is taking that extra step to guarantee a certain percent of a silicic acid in those rice hulls, you really don't know what is in that material. It could be high amounts of phosphate, high amounts of arsenic, and high amounts of other nutrients that will move in when silicon's not present.
00:28:57
Speaker
And so what happens when you take those rice hulls and you supply them to another hyper accumulator, say like cannabis, and you don't have that silicon source, what it's going to do is it's again going to hyper accumulate and draw those heavy metals or those nutrients that have a similar chemical profile as silicon into that system. Even though you might see negligible levels of arsenic,
00:29:27
Speaker
but you're not providing the silicon for the plant to outcompete, or the silicon to outcompete those heavy metals in. And so that's where I think we're getting into some of the problems that we're seeing. Growers, suppliers, everybody's wanting to do the right thing, but I think we still need more education on how to test for silicon, how to know what it is. So I don't think,
00:29:55
Speaker
Again, that anyone's doing anything maliciously, I think it's just the education isn't there in the thought process on how we should be testing these types of materials and certifying them prior to marketing as a media supplement.
00:30:16
Speaker
Yeah, I think you really touched on something there. And that's one thing I think growers have this first question. Well, how much of this do I apply? And how do I know how much to apply?
00:30:29
Speaker
I think, what's the answer to that? I mean, really, I think anyone out there marketing any type of nutrient or additive, we need to have that answer.
Challenges in Soil Testing for Silicon
00:30:42
Speaker
Like, well, what are we starting with? And we need to start typically in field soils, we need to start with a soil test.
00:30:49
Speaker
Is there an acceptable soil test available to farmers so that way they can get a proper baseline and then walk through the process of, okay, I know where I'm at. Now, the next question is, where do I need to be and how do I get there?
00:31:06
Speaker
And that's a great, again, I'm a cellular molecular biologist, so I'm going to answer this question as best as I can. And this is where, again, Brenda Tubano at LSU has been working with coming up and modifying, as well as other researchers around the world, these different extraction techniques. And how does that correlate? Because just like everything, it's going to be an extraction technique.
00:31:34
Speaker
probably about three or four different ones that they're all decent, depending on what type of soil you have. And then you get a value from that. And really, the thing is, if you find an extraction technique that you can see response as you add more, stick to that extraction technique, because they're all going to be different. But right now, I think it's an acetic acid extraction that they're using as kind of a baseline. But again,
00:32:02
Speaker
This is just looking at things like a rice down in Louisiana and Louisiana soils. So rice, wheat, maybe corn, but not all the different commodities or all the different plant species that we might be looking at and how that might go about. So it's still, I wouldn't say it's in its infancy because they have been working on it, but I haven't seen anything that's really been a true
00:32:29
Speaker
you know, this is a recommended soil test. These are the recommended values that we see for our NPKs and all that. But I do think that they're getting really close to coming up with those recommendations and starting to put some of those thoughts out into more crops other than just your row crops. Gotcha. Yeah, I guess as long as the test is accurate, you get an accurate
00:32:58
Speaker
baseline. But it can be accurate can also be incorrect correction test. Yes. Yeah, right. It's gonna be as accurate as the test method. So yeah, exactly. A lot of there's
00:33:15
Speaker
quite a few different methods out there. And again, it's just coming up with a method that works with the soil type that you're dealing with. And I think that's really what it's going to come down to. But again, not an agronomist. So this is just me kind of as I've been reading the literature and following that side of things.
00:33:34
Speaker
Yeah. Well, I have to get Brenda on too and ask some of the... There you go. ... questions going. There you go. Well, let's get back to benefits on what's acceptable on a label. I think you do some work with ATHCO, which is what the American Association for Plant... What is that?
00:33:54
Speaker
American Association of Plant Food Control Officials. There it is. Right. Right. And they kind of set the definitions of what's acceptable for labels. And in the United States, we have this awesome system where every state has their own system. So one label may be approved and acceptable in one state, but not in another, which having done product registration before is
00:34:22
Speaker
It can be a little frustrating at times, but I know they mean well, and I know the states mean well, and I think we're getting better as time goes on.
00:34:34
Speaker
But that being said, so some of the benefits of what's acceptable is, I think, abiotic stress relief or strength and structure, I think might be paraphrasing there. And a lot of people recognize that adding silicon provides strength and structure. But what does that mean?
Silicon and Plant Resilience to Stress
00:34:51
Speaker
What are we talking about when we're dealing with abiotic stress relief as it relates to silicon in your plant? Help us understand that.
00:35:02
Speaker
Okay, so on the aspect of APCO, they recognize silicon as a beneficial substance. So in the US, silicon is regulated as a plant fertilizer. And so that's why it falls under APCO. If we would talk about pests and disease, which I will after we talk about abiotic,
00:35:26
Speaker
it would have to be registered as a pesticide and that would go through the EPA. And so with silicone being a nutrient, we're not going to get into the nuts and bolts. But really, so what you'll see on labels is the abiotic responses. So we're talking about
00:35:45
Speaker
anywhere from environmental stress, like temperature, so weather, frost, heat. We get into things like drought, salinity. And I had it all in my head in this beautiful order that I wanted to talk about.
00:36:03
Speaker
With the abiotic stress, silicon really has a broad response at mitigating all of this. And really, it's because what silicon is doing is it's balancing out the plant, it's balancing out the nutrients, it's balancing out the water. So your plant can respond in a positive way to all of these different environmental shifts that cause a similar internal imbalance within the plant.
00:36:33
Speaker
So what you'll see on a label, you know, they talk about stronger, thicker growth. You don't always see that. I can say the majority, I have never experienced a thicker stem with silicone treatment my entire career yet. And we've worked with a lot of different plant species. And I'm not saying that those studies that have seen an increase didn't, they definitely did because the data is there. I just have not experienced that myself.
00:37:03
Speaker
But what you do see is that the plants do have
00:37:09
Speaker
almost more tensile strength and this is because the cell walls, the matrix has a different organization and it's not that it's silicon that's being deposited there because that's one thing everybody, oh silicon deposits and it gives it this really, it's this rigid castle and it's super super strong. That isn't the case. Silicon's present within the cell wall but it's really
00:37:33
Speaker
What I think we're going to see, and again, this is just, we're inferring at this point because we don't really have a lot of microscopy. We don't have direct science that shows what silicon's doing in the cell wall. But when we think of cell walls and those that are stronger than others, it's the cross-linking of these different components in that cell wall matrix. And I do believe that silicon's role, if we look at plants, the concentration is
00:38:02
Speaker
similar to those of the metals, the essential metals that we have. So I think silicon's playing a role in enzymatic activity. And enzymes in that cell wall or the apoplastic area are very important in how the cell wall is cross-linked, which gives it strength. Cell walls are also important for water movement and solute availability. And so it can also change the chemical characteristics of that cell wall.
00:38:30
Speaker
And so again, its silicon is really tied strongly to the water status and the water balance throughout the plant. And again, that's going to help when we think of reducing the concentrations of contaminants, water movement, transpiration movement, getting nutrients like calcium to certain areas that might be deficient.
00:38:53
Speaker
The strength is coming, I think, from that cell wall architect, the matrix being different when silicon's present than when it's not, not necessarily that silicon's depositing and you're getting a glass shell within the matrix, but it's definitely doing something at the matrix level that's going to that.
00:39:15
Speaker
And then the other responses that we're seeing with temperature changes with all of, and we see there are changes in gene expression in that, but it's really because when we feed plant silicon, they deal with the stress really well. So they become, if we think of it, a person much more laid back. Stress really doesn't bother them. They take it on. They're like, okay, it's cold today. We're good. Just going to turn up my internal heat a little bit more and I'm good to go. And it, they don't really, um,
00:39:44
Speaker
stress or they don't have such a dramatic effect as plants that do not contain silicon. So kind of like having a more robust immune system in a sense, just more vigorous. Maybe that's the right
00:40:03
Speaker
and a faster response time. So it can change and adjust small changes more quickly. And so those little changes, kind of like the butterfly effect, the little changes at the very beginning have dramatic end effects on the quality. And it's really, it isn't so much yield as part of that, because if you'd reduce stress, you're going to increase yield. But the quality we're seeing in these plants, when we start putting silicone back, you get to those genetic potential of the plant.
00:40:33
Speaker
we're enhancing the quality characteristics, which then lead to enhancements in yield, especially when you're under those stress conditions.
00:40:44
Speaker
I'm so glad you said that because that really ties into, I've heard that question before, how do you maximize yield? And there were several years ago, I was attending an ag trade show and their keynote speaker, he was the highest yielding corn grower, I think in the country or in the state or something. I think it must have been nationwide. And they asked him, how do you achieve highest yield?
00:41:11
Speaker
genetic, full genetic potential. I said that plant can't experience a day of stress and that's life. That means drip irrigation. You got to really dose that water so that it doesn't experience water stress, so on and so forth. Silicon, this is one more piece to that puzzle of reaching full genetic potential. And that's right because any type of stress is going to hamper yield potential. And I think you've explained
00:41:39
Speaker
many reasons why having silicon present at appropriate levels helps. It may not be a silver bullet, right? However, it definitely helps. If we were to write this out into an equation A plus B plus 2N equals highest yield, silicon is in that formula somewhere, or it needs to be.
Including Silicon in Plant Nutrition Plans
00:42:02
Speaker
Right, just like any other balanced nutrition plan. The problem is we know we need to put all these other nutrients in. You know you need those micronutrients if they're lacking, you're going to be lacking. But we never think about silicon in that nutrient context. And that is the key there is that it isn't an end-all, but if it isn't there, this is reducing your yield and it's causing you to use some of these more expensive
00:42:32
Speaker
fertilizers, the nitrogen and the phosphate to bump and get those yields up because that's what we're seeing a lot is you can reduce the nitrogen, you can reduce the phosphate that you're fertilizing with when silicon's present. And the reason is silicon is taking care of its balance out and so you don't need to push production with those higher fertilizer inputs that we typically see to get us to those
00:43:02
Speaker
projected yields. Do some species of plants, do they maintain a reserve of silicon in their roots if they need it or do they just take it up as on demand?
00:43:17
Speaker
So we did a study in tobacco years ago, and that was our question. Because when we look at dicot species that take up about a thousand parts per million in their leaves, they actually have really, really high concentration of silicon in the roots. So I did a deep water hydroponics study with tomato. We found some of these tomato species had 3% silicon in the root tissue, but only about a thousand parts per million in the leaf.
00:43:47
Speaker
So 3% is, sorry, 30,000 parts per million versus a thousand parts per million. There's my math. So what we thought was, okay, if they have these high concentrations, maybe we can load the roots up, stress the plants, and they can use those reserves. So what we did is we took the tobacco, we grew them again in these deep water systems, we grew them under high amounts of silicon, and we were using copper stress as our
00:44:16
Speaker
stress at the time. And so we then divided them out. What we found is there was not, when we took silicon away, there was no silicon movement. So that concentration of silicon that's present within the roots are in areas that it's not at a high enough concentration to move out. So it
00:44:37
Speaker
They're likely tied up within the cell wall within the vacuoles of cells or within other cell structures that we're not really aware of. The other thing could be that
00:44:48
Speaker
again, without it moving into the central portion of the root tissue, it will equilibrate out. So even though we loaded it up with high concentrations, when we put it into that silicon free solution, that silicon could have moved out to equilibrate into that. And so we did see slightly more silicon in the plants that were preloaded, but it was significantly lower.
00:45:12
Speaker
than those plants that had the available silicon at the time of the stress. So this, when, again, these are in those thousand parts per million or lower, when we look at things like rice or hyper accumulators, cannabis is probably the same way. The root concentrations are really, really, really low. And they're probably really low because unlike
00:45:36
Speaker
these other plants, they don't have as high type regulation of that arsenic B or that LSI2 transporter. And so all the silicones that's present, they're just continually sucking it up out of the system. So I would guess with those type of plants also, you're not going to have a root reserve of the silicic acid. And that's why we really do see the responses that if the silicic acid is present at the time of stress,
00:46:06
Speaker
we see that positive response. So it has to be there when the stress is present. It isn't something that you can come back and fix after the fact. Gotcha.
Understanding Silicon Product Labels
00:46:21
Speaker
I want to touch upon products a little bit without naming any, but you've evaluated
00:46:29
Speaker
many silicone products out there, quite a few. I think a lot of people, a lot of companies have approached you to evaluate their product. Regarding labels.
00:46:40
Speaker
Again, there's differences between states. As time goes on, I think it's getting better from my experience, and I think California kind of leads the way in this in a good way. I think that what they're looking for now or what they accept is soluble silicon, granted, maybe without getting into the analysis of how that's derived, because that could change things.
00:47:06
Speaker
There's so much variation on labels, at least historically there has been, and also derivative statements. I can't tell you how many times I've been asked from people, well, this is potassium silicate or calcium silicate or monosolicic acid or orthosolicic acid. That creates so much confusion with end users. That's the question I get the most. Well, what do I have? Is this better? I hear this is better. Why is it better?
00:47:34
Speaker
Oh my goodness, we really need to break it down to its simplest component. Can you help shed some light on that and what users need to look for to understand for those labels? Yep, I can. So with the labels, really what you want to do is look at percent SI. So right now in the US, the percent value has to be of the salicic acid.
00:48:01
Speaker
Prior to, so maybe about 10 or 15 years ago, they were using total silicon as that value. They no longer do. So when we see percent SI or a percent of some kind of silicon form on a label, that is referring to the silicic acid fraction.
00:48:19
Speaker
Whether that salicic acid is coming from calcium silicate, rice hulls, and amorphous form will last night any type of these products. It doesn't really matter because that's putting everybody on the same playing field. So it's telling you how much monosolicic acid is in that product based on the extraction test.
00:48:40
Speaker
Not all states require it to be percent Si. Some will allow them to put percent SiO2 and percent salicylic acid, which is Si with OH4 or H4SiO4. All that's telling you, again, you want to make sure that you are looking at every product with that percent Si. So when we think of Si to SiO2,
00:49:06
Speaker
That's about two times higher if they're putting percent salicylic acid. That's about three and a quarter to three and a half times higher than percent SI. So they can use that to kind of bump their SI numbers. But really, you're looking for that percent SI and comparing that across all of the products is going to tell you apples to apples what that product has the ability to do.
00:49:32
Speaker
It gets a little tricky when we think about solids versus liquids because the solid percent Si is going to give you kind of what's going to be available over a long range. So it's not all available at once because it has to break down to release that salicic acid in. When we look at liquids, however, it
00:49:54
Speaker
is what is available at that time. And so with the liquids, if you're doing like
Liquid vs. Solid Silicon Products
00:50:01
Speaker
a Beto bucket system where you're fertilizing and it's going to waste, you want to make sure that all that silicone right there is going to move out of the system because it's in the soluble form. So it's going to move out with the waste. It's not going to bind to whatever solid substrate you might have in those type of systems.
00:50:18
Speaker
But that percent SI is the key to starting to compare these products to one another. Because whether it's coming from rice hulls, whether it's coming from last night calcium silicate products, potassium silicate, calcium silicate, amorphous silica, or simply they'll say it's coming from silicic acid. Well, it does get confusing. I get confused all the time. And really, I'm just looking for what that percent SI
00:50:48
Speaker
says and that's how volcanic ash or ancient seabed or really the silicon levels. So if for some reason there is a label out there and it lists percent monosolicic acid, let's say it's SiOH4 on there, really somebody looking at that, let's say it says it's 4%, wow, and they compare it to another one that has percent Si and it's one, essentially they're similar in their
00:51:17
Speaker
They're pretty similar, right? And the other thing is, and I'm probably jumping on this one too, when we think about application rates.
00:51:26
Speaker
1% SI is again, 10,000 parts per million. I usually recommend adding it at 30 to 60 parts per million, because again, if we think about solubility in a soil system, what these plants have evolved to be able to accumulate at any given time is within that 0.2 to 25 parts per million silicon.
00:51:53
Speaker
In our research in the lab, we usually add in silicon at a high end of 2 millimolar, which is right at about that 60 parts per million silicon. So putting in any more than that is really saturating the system. So if you're thinking about what's better, a 1% or a 5% SI, well, one, you're just going to be diluting a lot more. So really, that's where a 0.2% silicon product
00:52:22
Speaker
is a good silicone product. You're going to get what you need. You're just going to have to add it at a higher rate than you would a 1% or a 10% and so on. Right, and compare the application cost. Correct. So what if it's four times higher? Is it four times less? The cost per finished gallon of solution, what is it? Right. Yep. Yeah. So many products out there, I noticed
00:52:50
Speaker
some of the drawbacks to some silicone products. High pH, so you have to adjust pH. I don't know if that tends to be a challenge or not, kind of caustic, but gelling seems to be a problem. Is that because of the solubility of silicone? Is it high pH? Is it trying to achieve that amorphous stature? You mentioned kind of the jelly earlier with amorphous silicone.
00:53:16
Speaker
really seen with the potassium silicates, not that it's just a potassium silicate issue, but potassium silicates were probably the most sold liquid here in the US. And so what really is happening as the pH, so it is a high pH to keep the silicic acid in solution,
00:53:35
Speaker
When it comes down and gets within that pH of six, the silicone loves to interact with itself. So at that pH of six, it will start interacting and polymerizing with itself. And if you sit at that pH six for too long, that's when you get the gel, that's when you get the issue. And so with those types of products, they do encourage, if you're going to bring it down, adjust the pH either before you add other nutrients or
00:54:03
Speaker
make sure when you're adjusting that pH it's a quick drop and then bringing it a quick drop past that pH of six because that's really that's the sweet spot where really really bad things happen. I can say that I've worked with potassium silicate. I've added it to my fertilizer solution with the complete with the fertilizers already diluted out. It kind of clouds up because of the high pH. I drop the pH and it goes into solution
00:54:29
Speaker
I have not had any problems just with how I've ran them, but that's where they always say a jar test, always perform a jar test before you fill up that big tank full of this solution just in case something were to happen. But
00:54:44
Speaker
That's where, you know, the formulations, because everything, where I talk about silicon and silicic acid, many of these products, there's a lot more than just the silicon. So you're not just seeing the silicon benefits, but you're seeing the benefits from the other additives that are present within there. And so that's another thing to think about.
00:55:05
Speaker
when you're comparing these products, it isn't always just silicon. So there are some other formulations and other benefits with certain formulations over others that might have a better response in your growing system. Yeah. In the research, have you done any work with, we talked about monosyllic acid,
00:55:32
Speaker
into some of the research papers I've reviewed and some products out there, you're starting to see nanotechnology and nanostructured silica, which is SiO2, but the way I understand it is those molecules have side chains, because like you said, silicon likes to, it sounds like it's social, it likes to intermingle with itself.
Potential of Nanostructured Silica in Agriculture
00:55:56
Speaker
So you have these structures and what makes it nano is the side branches because it kind of looks like a bunch of grapes underneath the microscope. What's the name for that?
00:56:10
Speaker
cells in the plant. Once silicon is deposited into the cells, you get the phytoliths. Is that what it is? Oh, yeah. Yes. Yeah. So once silicon is a bio-silification, that's so much fun to say. So nanostructured silicon, they have these side chains and the branches are, I think, less than 100 nanometers, which a nanometer
00:56:31
Speaker
what, a billionth of a meter? So very, very, very small. Have you done any work with nanostructured silica? It seems like it might be something that's kind of up and coming and gaining traction. I haven't. I would love to. What's interesting is the term nanosilicon or nanosilica is widespread. So kind of like biochar, we're starting to see there are a lot of products that are claiming a nanosilica
00:56:59
Speaker
products, rice hulls actually can fall under nano silica. And so it is with these products, whether they're synthesized in lab or they're from naturally derived phytoliths, they do have kind of a different characteristic than we see with silicon in from a parent material in a soil profile.
00:57:23
Speaker
But again, they do break down, they do release. I haven't worked with them yet. I would love to. I kind of extended right now with this time. But they do move differently in a plant system. And so we are seeing that a lot of these are fully replied. And they do see that some of these are moving in through the stomata and getting into the apoplastic area, where the outer part of that shell could be releasing the salicylic acid.
00:57:53
Speaker
But they could also, with silicon, it opens up all these binding sites. So when you think of clay material in a soil profile, it has all of these sites for cations to bind to and different nutrients. We don't know what type of proteins or enzymes. We do know that in the lab, so in cellular molecular biology, we use silica columns when we purify DNA.
00:58:20
Speaker
or RNA. So nucleic acid does bind to silica. And so there's a lot of potential
00:58:28
Speaker
for what these particles might be doing when they get into the cell. It's likely going to be different than what we see with silicic acid moving. But again, we don't know once silicon is getting into the cell wall matrix, if it's setting up its own kind of amorphous little substructures within the environment. Again, this is what I said. Silicon, we know so little about it, and there's so many.
00:58:53
Speaker
But from the nanotechnology side, they are seeing benefits to it. They're seeing benefits in germination, in tomato, and in other things. So even though we don't understand the technology yet, there does seem to be a role and a beneficial role, but it is separate from what we see with the salicylic acid.
00:59:15
Speaker
But I do want to add a caveat to that. Again, not all silicon nanostructures are the same. So they do see it really comes down to the size and how it's probably formed that play a role in whether or not you're going to see a benefit from it. So not all nanoparticles are going to show you the benefits that are in the literature and you really need to understand
00:59:40
Speaker
the size profiles and what the data is with that particular product, what have they seen with their product, not what have other people seen with nanomaterial. And that's going to be a much stronger case for the beneficial response you'll see if you incorporate those types of material in your growing system.
01:00:00
Speaker
Thanks for expanding upon that. I was privileged to have worked with some nanotechnology in the past and nanostructured silica. Anecdotally, I saw some interesting things, although it tended to be in combination with other technology. The question became,
01:00:24
Speaker
How much is that contributing? I believe it was contributing, but I couldn't really explain how and to what extent. I think there's something there, but this just drives home the data. You've got to have some data and it needs to be not... Is it compounded or compounded? It needs to be separated. You've got to make sure you have the right treatment so that way you're not
01:00:49
Speaker
interacting with other factors. So I'm excited about that because I'm always excited about new technology and how it can help growers become better at what they do and push the market forward, make healthier plants, be able to either produce more plants, they like ornamental production, they have more plants, maybe they last longer for the consumer. Maybe one point to make is a lot of what we've discussed here today
01:01:17
Speaker
Regarding silica, it applies to whether the plants are grown outdoors, in the soil, soilless media, greenhouse, whether it's corn, cannabis, petunias, sunflowers, it's applicable to all crops. So if you're growing in greenhouse agriculture and you're asking yourself, is silicone beneficial to me? Yes. The answer is? Yes, even more so. You're probably lacking quite a bit.
01:01:42
Speaker
Right, right. I've said this many times. I'll say it again. The only thing missing from soilless media is the soil and people look at me kind of funny and they will die. And the reasoning behind that is the more we discover about soil, it's not just an anchor for plants and nutrients. It's so much more than that. We've got to add that back into soilless media. Yup. I think Jonathan, Jonathan France always said, you know,
01:02:08
Speaker
from the day that they took the soil out of the media, they've been trying to figure out how to put it back. Yeah, what a great guy too. I need to reach out to him. I haven't seen him for years. He was always so welcoming, just an all around good dude.
Conclusion: The Importance of Silicon
01:02:25
Speaker
He's in Iowa now, isn't he? What's that? He's in Iowa now, is that right? Yeah, that's what I thought. Okay, anyway, we kind of went off track there a little bit. Sidebar.
01:02:37
Speaker
Well, hey, when somebody like that pops up, give them kudos where it's due. Well, I think we've covered a lot of ground today, literally and figuratively. Not literally, figuratively. Anyway, is there anything else you want, any other points you want to make?
01:03:00
Speaker
Um, not at this time, but really, you know, again, trying to get this education out and thinking of Silicon as a nutrient. Silicon is a nutrient and it is a very important nutrient for all plants. And so just understanding, um, if your system is lacking, uh, how to get it back in there and what the bet, you know, how
01:03:21
Speaker
how to work it in again to increase that quality. And the increase in quality is going to help you with increasing yield or getting you to where you want to be with the plants that you're growing.
01:03:37
Speaker
Awesome. I couldn't agree more. Speaking of education, and I know I've asked you this before, so I'll put you on the spot again. Where can people, can they, are you active on social media on LinkedIn or maybe just where can people find the papers that you've contributed to? You have many peer reviewed papers or maybe suggest some others. Well, so I do have a LinkedIn profile.
01:04:04
Speaker
You can email directly. My email address is zellnersrsoz-e-l-l-n-e-r-s at outlook.com.
01:04:17
Speaker
And I can, you know, if you have specific questions, we can start a conversation that way. But LinkedIn is probably the easiest way to find me. Just look for Wendy Zellner. I'm still an adjunct and an associate research associate professor with the University of Toledo. So if you wander on their website, you might also find my contact information there as well. And so that email is still up and running. But just
01:04:45
Speaker
or reach out to Johan, you know? And he can... Yeah, reach out to me. I'll tell you how to find her. Right, right. So those are... I'm not as active as I'd like to be, just very busy with other things, but I do have it. Understood. Yeah. Yeah. Well, having a LinkedIn profile is a great way to start. I don't have a website up yet. And so when I list what's your website, I just direct them to my LinkedIn profile. And that may... I may keep it that way. I don't know.
01:05:15
Speaker
There's so much great information there and you can post, you can, I think they even have a contributor section now where you can write articles and post them there. So I just leave that as my go-to resource for people. Just go to my LinkedIn profile. So you got that going. Right, right. Well, good. Well, as always, wonderful to visit with you and thank you for sharing
01:05:43
Speaker
Your knowledge and the current status of Silicon is based on your experience, and thank you for your contributions, and I'm sure we'll be chatting again. And if you'll just hold tight, we'll sign off. And once again, Dr. Wendy Zellner, thank you so much. Thank you. All right.