How a Solar Root Stimulator Can Help Grow Healthy Plants

An electrical root stimulator may stimulate plant growth in the absence of bright sunlight.
By TJ Byers
January/February 1984
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A solar cell is more efficient than photosynthesis at converting sunlight into energy.
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Everybody knows that there's nothing better than sunlight for promoting plant growth. Or is there? Well, there may not be anything that can actually replace ol' Sol . . . but could there be a better way to use sunlight to help plants grow?

If recent scientific studies on an electrical root stimulator bear out in the real world, the answer is . . . yes! These controlled laboratory experiments have produced heartier plants and bigger harvests. Sound exciting? Then let's dig into the details of this potential breakthrough.

Plant Growth 

Before a leaf can turn the sunbeams it absorbs into food (a process known as photosynthesis ), it must have a source of raw materials. Nutrients are absorbed from the soil by the plant through a vast network of roots . . . intricate structures that contribute as much to a plant's growth as does sunlight.

As a matter of fact, an average plant's root system is fully as large as the structure it supports. Few people are aware that a healthy four-inch-tall plant can be expected to have roots that extend at least four inches below the ground. Of course, this isn't true of all plants, but it's the norm for most productive crops.

Now since the top half of a plant is dependent on the bottom half, it seems logical that stimulating the growth of the roots might lead to a proportional increase in the size of the greenery above. As you'll see, this appears to be the case. Through a process that isn't yet thoroughly understood, mild electrical stimulation of a plant's roots can indeed promote the growth of the entire organism.

One theory for the phenomenon holds that the electrical stimulation actually supplements the energy received from the sun. But whatever the reason may be, documented studies show that plants that receive electrical root stimulation often grow faster and are heartier than those raised without the treatment.

PV And Photosynthesis

Naturally, electrical root stimulation requires a source of power. And what better source of free electricity could you ask for than a photovoltaic solar cell?

As in the photosynthetic process, a solar cell absorbs a photon of light and converts it into energy . . . electrical, in this case. Unlike photosynthesis, though, a solar cell does a much more efficient job of converting light into energy. A typical PV cell, such as the kind you can find in a Radio Shack store, converts at least 10% of the light it receives into electricity. Photosynthesis, on the other hand, is hard pressed to turn 0.1% of the available light into energy.

Root Stimulation Results 

Experiments done at the University of Maryland show that if the output of just one solar cell is fed to a plant's roots, a sizable increase in growth can be expected. In one test comparing growth in salvia plants, the experimenters began with 26 samples and subjected 14 of them to electrical stimulation from a PV cell. The other 12 served as a control (or baseline) and were cared for in the same way the stimulated plants were.

At the end of four weeks, the experimental group averaged 10 1/2 inches in height, while the control group averaged only 5 1/2 inches . . . demonstrating that stimulated plants grew almost twice as rapidly as "normal" ones!

Other tests have shown that through photovoltaic treatment a plant can be pushed to an early bloom. One course of investigation even subjected sickly greenery to root stimulation. The result of such solar "shock therapy" was a marked improvement in the condition of the specimens!

Experiment at Home

If this sounds too good to be true, you don't have to take my word for it. Why not try it yourself? Although I can't guarantee startling results for you—there's just not enough known at this time—I will promise that you'll have a good time with your experiment.

First, you'll need to obtain a photovoltaic cell suitable for the test. Although you could assemble your own solar generator from readily available parts, I recommend that you purchase a Sun Stik from Silicon Sensors, Inc., for about half of what it would cost to make your own. [EDITOR'S NOTE: Resourceful readers who have access to surplus cells may be able to beat Silicon Sensors' price . . . simply attach electrodes to the two leads on the photovoltaic disk. If you do decide to build your own, make sure that the silicon cell is completely protected from moisture.] 

For the most accurate results, you should begin your experiment with two identical plants. Set them in separate pots, and push the metal rods of the Sun Stik into the soil of one of them. Place the two competitors in an indoor location where they'll receive about the same light, and water and care for them equally. After around 30 days you should notice an amazing difference between them: The solar-powered plant ought to be larger and have more foliage.

The Catch

"Ah," you say, "I knew there'd be a catch. It is too good to be true." Not exactly, but the catch is that the root stimulator works best on plants that aren't exposed to much sunlight. Those studies I mentioned before showed that foliage exposed to bright sunlight receives little or no benefit from root stimulation.

Why? Probably because photosynthesis can supply enough energy in bright sunlight to serve all the plant's needs. Photovoltaics only offer a significant boost when other sources of light are reduced or unavailable. In other words, it probably wouldn't do much good to pepper your cornfield with Sun Stiks.

But remember that a solar cell does a more efficient job of converting sunlight into energy than does photosynthesis. PV, then, can generate usable amounts of electricity under lighting conditions that would be useless to the leaves of a plant (this includes fluorescent and tungsten lamps used for everyday indoor illumination). So imagine what a solar root stimulator might do for that fern hanging in the den!

Practical Uses 

Besides perking up light-starved houseplants, what practical applications might a PV root stimulator have? Well, for one, tests have shown that seeds placed within an electric field sprout more quickly and are more prolific. So if you used a solar disk on your starts, instead of having—say—only 50% of your seeds germinate, you could expect a success rate of 75% or better.

Second, root stimulation works particularly well on seedlings, so a solar cell could be able to help you germinate and raise your starts indoors before the spring thaw comes. When it finally warms up enough to put your young plants out, you'll have a good jump on a healthy garden, one that has hearty, substantial stock rather than fragile, underdeveloped seedlings.

More research needs to be done on this exciting new process. But if you want to do a bit of investigating yourself, the investment is small and the work's relaxing. Who knows, with a little imagination and honest effort, you just might come up with the application this technology is waiting for!


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