John Kempf explains how boron functions in plants by providing the driving pressure that moves nutrients—especially calcium—and sugars from roots toward the plant tips. Generous boron levels promote upward translocation of calcium and sugars, speeding senescence and maturity (true dry down) and concentrating sugars in grain/fruit; boron deficiency keeps calcium and sugars in lower leaves and impairs these processes.
Chapters
One of the things that I observe a lot of is plants that don't have enough boron or that behave in ways as though they didn't have enough boron. So I want to describe a little bit about how I think about boron functioning in the plant. You know, years ago I developed this concept of what's the one thing that we need to know about a mineral in order to be able to manage it? Well, because you can easily put together a list of the 20 things that Boron does that are important or that calcium does that is important. But what is the one thing you need to know about each mineral to manage it that's important. And I want to talk about the one thing you need to know about boron. In a previous short clip, I spoke about how boron is not flow immobile, and therefore it's best to get it from the root system. But the one thing to know about boron is that boron provides pressure to move nutrients, but particularly sugars and particularly calcium around in the plant. So if a plant has generous levels of boron and it picks up calcium down here, it's picking up boron down here from through the rise of 80 cycle rate, even ionic calcium. When it has generous levels of boron, it will push that calcium up through the plant all the way up to the upper tip. And you have generous calcium levels here at the top, at the furthermost tip. And that's also where they'll have boron as well. This is why, when you have boron toxicity, boron toxicity shows up as burning at the tip, because that's where the boron goes. And given the opportunity, it will carry calcium with it and it'll push calcium outward. Now, if you have a plant that doesn't have enough boron, calcium levels will be in the lower leaves. They end up here in the lower parts of the plant. And they don't move upward, so you don't have the strong upward and outward pressure. The same is true not just of calcium, but also particularly of sugars. So we should think of boron. Boron is not the engine that drives sugar translocation, but in a sense, it provides the pressure. So if you get close to maturity, for example, when a plant naturally senesces and you want to move sugars out of the leaves and into the grain or into the fruit. Take a corn plant for an example, or a small grain. When a plant has generous levels of boron, the sugars will all move out of the leaves and they will concentrate in the ear and you get sugar concentration here. And what happens is you have a plant true dry down means that the leaves will senesce and turn brown, lose chlorophyll, lose moisture, lose nutrients because all the sugars moves out of the leaves and into the grain. And you still have, you have dry grain on a stalk that is still green and has high moisture content. That's true dry down. Conversely, most plants today don't dry down. Instead they die down where you have grain that has a low moisture content but leaves that still have high moisture content. So think about boron as driving, as putting pressure on sugar movement. It speeds up the sugar movement that the plant would do naturally anyway. So it will speed up maturity, it will speed up senescence and it will provide pressure to move nutrients, particularly calcium, from the root system upward to the farthest, most tips of the plant and give us the healthiest plants and the highest quality fruit and the highest quality seeds.
