Tobacco Plants Tapped to Grow Solar Cells
When injected with an engineered virus, tobacco plants are forced to create artificial chromophores.
Norbert Nagel, Wikimedia Commons
Medical marijuana gets all the headlines, but many legal weeds have traditions as medicines too. Although homeowners often consider these plants as lawn outlaws, weeds can serve as a floral pharmacy. However, would-be patients of the plants should consult a doctor before self-medicating.
Cichorium intybus, the light blue flower frequently seen along roads, provides the main commercial source of the compound inulin. Patients take inulin to fight high blood fats, including cholesterol and triglycerides, according to WebMD. Research published in Diabetes & Metabolism Journal suggests that inulin intake benefits women with type-2 diabetes by reducing the rate of blood sugar increase after eating. Inulin promotes the growth of certain bacteria in the intestines. While some believe this can help digestion, others suffer serious flatulence when the inulin-fed bacteria build up.
Some people add the dried and roasted root to coffee. Chickory coffee is especially popular in New Orleans.
Böhringer Friedrich, Wikimedia Commons
Trifolium pratense contains chemicals known as isoflavones. These chemicals can act like the female hormone estrogen in the body. Doctors have examined the clover chemicals as a treatment for hot flashes and other symptoms of menopause. However, doctors warn that women with a history or risk of breast cancer should avoid isoflavones, since estrogen-like chemicals have been associated with increased incidence of some cancers.
H. Zell, Wikimedia Commons
Silybum marianum has a 2,000 year history as a liver medicine. Modern research has looked at thistle extracts as a treatment for alcohol-induced liver damage. Substances in milk thistle, particularly the chemical silymarin, may protect the liver from damage after a person takes an overdose of other medications, including acetaminophen (Tylenol). Milk thistle may also be an antidote to poison from the deathcap mushroom (Amanita phalloides). Animal studies found that milk thistle completely counteracted the poison if given within 10 minutes of poisoning, according to the University of Maryland Medical Center.
Muffet, Wikimedia Commons
Native Americans used the milkweed (Asclepias sp.) as a contraceptive, according to the U.S. Department of Agriculture. The milky, white sap that gives the plant its name served to remove warts. However, milkweeds also contain chemicals known as cardiac glycosides. These chemicals can cause severe illness in humans and livestock. Monarch butterfly caterpillars eat milkweed and build up high concentrations of glycosides, which makes the insects nasty tasting to predators.
Tony Hisgett, Wikimedia Commons
Ancient Greeks and Romans used horsetail (Equisetum arvense) to stop bleeding, heal ulcers and wounds, and treat tuberculosis and kidney problems. My wife drinks horsetail tea to flush out her body’s system and help lose weight. The tea has a mildly bitter flavor, similar to chamomile. Research published in Ethnopharmacolgy found that horsetail tea increases urination which corroborates my wife’s contention that the plant is a diuretic, or a substance that increases urination. However, doctors recommend taking a multivitamin when drinking significant amounts of horesetail tea, because it can flush nutrients, such as vitamin B1, thiamin and potassium, out of one's system as well.
J. Carmichael, Wikimedia Commons
In the past, Europeans used remedies made from dandelion (Taraxacum sp.) roots, leaves and flowers to treat fever, boils, eye problems, diabetes, and diarrhea, according to the University of Maryland Medical Center. Practitioners of traditional Chinese medicine take dandelions for stomach ailments and breast problems, such as inflammation or lack of milk flow. Dandelion leaves taste similar to spinach and contains vitamins A, B, C, and D, along with iron, potassium, and zinc.
Uwe H. Friese, Wikimedia Commons
Urtica dioica can put the hurt on an hiker in shorts, but historically the plant has served to treat aching muscles and joints, eczema, arthritis and gout. People still use the plant to treat joint pain, and some studies have suggested that the plant can treat arthritis. Another study found that capsules of dried stinging nettle may reduce the symptoms of hay fever. Europeans frequently use stinging nettle root to treat bladder problems. Boiled nettle makes a side dish similar to collared greens.
For those who brush alongside stinging nettle, a remedy to the sting is often found growing nearby. Applying crushed up dandelion, horsetail, Aloe vera, jewelweed or the leaf of a dock or lock plant can counter the acid in the sting.
Forest and Kim Starr, Wikimedia Commons
Like many of the medicinal weeds in this list, purslane (Portulaca oleracea) also makes a healthy snack. The plant contains a high content of omega-3 fatty acids. I ate some that grew in my yard and found it was somewhat sour. A little bit was good, but too much would be overpowering in a salad. In traditional Chinese medicine, purslane treats genito-urinary tract infections. Research published in Phytomedicine found that the plant reduced problems with cognition in older mice.
Robert Steers/NPS, Wikimedia Commons
Since the age of the ancient Greek doctors have used plantains (Plantago sp., the weed in sidewalk cracks, not the fruit) to speed wound healing. In the training manual Survival, Evasion and Recovery, the U.S. Department of Defense recommends plantain as a poultice on wounds or as a nutrient-rich tea to treat diarrhea.
Julia Adamson, photographer in the Saskatoon area, Wikimedia Commons
Traditionally, healers use burdock (Arctium sp.) to clear toxins from the blood and increase urination, according to the University of Maryland Medical Center. The plant also is used to treat skin ailments, such as eczema, acne, and psoriasis. The leaves and roots of burdock are edible and contains inulin, like chicory, so they may aid digestion and/or cause a nasty case of flatulence. Burdock also contains high quantities of antioxidants that can prevent damage to cells.
Genetically engineered viruses injected into tobacco plants trigger the plants to grow solar cells.
- Synthetic solar cells can be grown in tobacco plants and E. coli bacteria.
- The method offers a cheap, environmentally friendly way to make electricity.
- Tapping the plants exploits an already efficient system, honed by millions of years of evolution.
Tobacco plants could help wean the world from fossil fuels, according to scientists from the University of California, Berkeley.
In a paper in the journal ACS Nano Letters, Matt Francis and his colleagues used genetically engineered bacteria to produce the building blocks for artificial photovoltaic and photochemical cells. The technique could be more environmentally friendly than traditional methods of making solar cells and could lead to cheap, temporary and biodegradable solar cells.
"Over billions of years, evolution has established exactly the right distances between chromophore to allow them to collect and use light from the sun with unparalleled efficiency," said Francis. "We are trying to mimic these finely tuned systems using the tobacco mosaic virus."
Synthetic solar cells don't just grow on tobacco plants. They have to be programmed to grow on tobacco plants. Reprogramming every cell of a mature tobacco plant would be a massive undertaking for human scientists.
For the tobacco mosaic virus, however, reprogramming adult tobacco cells to produce tiny structures the plant normally would not make is what the virus does best. The scientists tweak a few genes in the virus, spray it over a crop of tobacco plants, and wait.
Usually, an infected cell creates new copies of the virus that infected it. This time, the virus forces the plant to create artificial chromophores, structures that turn light into high powered electrons.
Like a tightly coiled spiral staircase, individual chromophores are added one at a time until a rod hundreds of nanometers long is created. Each chromophore is two to three nanometers away from their nearest neighbor, an important distance. Even one atom closer to each other, and an electric current would be halted. Any further and harvesting the electrons would be difficult.
"It's very difficult to recreate photosynthesis," said Angela Belcher, a researcher at MIT who uses viruses to build batteries and other structures. "The precision of each structure is very important, and it's very hard to pick up one molecule and put it where you want it to be."
When injected with an engineered virus, tobacco plants are forced to create artificial chromophores. iStockPhotoiStockPhoto
The beauty of the Nano Letters paper, says Belcher, is that it exploits an already efficient system, honed by millions of years of evolution, to produce structures for humans.
Trapped inside the plant, the tiny structures don't produce electricity or chemicals. To get at the synthetic chromophores, scientists would have to harvest the plants, chop them up, and then extract the structures. Dissolved in a liquid solution, the structures are sprayed over a glass or plastic substrate coated with molecules that secure the rods to the plastic.
Tobacco plants aren't the only organisms Francis and his colleagues have hacked. Skipping a virus entirely, Francis and his colleagues successfully added the chromophore-producing genes to E. coli bacteria, and harvested solar cells from them as well.
Using live organisms to create synthetic solar cells has several advantages over traditionally made solar panels. No environmentally toxic chemicals are required to make biologically derived solar cells, unlike traditional solar cells. Growing solar cells in tobacco plants could put farmers back to work harvesting an annual crop of solar cells.
Bio-based solar cells wouldn't last as long as the average silicon solar cell, but they could act as a cheap, transportable, and temporary biodegradable power source. A solution of them could even be sprayed over plastic or glass to harvest energy.
Plants are already very efficient at turning the sunlight into sugar and other forms of chemical energy. The UCB scientists could eventually use the electrons to generate chemical energy like plants, but instead of creating sugar, they would create hydrocarbons that could power cars or aircraft. A photochemical cell is one use for the new technology. A photovoltaic cell, that converts sunlight into electricity, is another possibility.
It will likely be years before any consumer devices use the natural, yet synthetic, solar cells, says Francis. The scientists haven't even demonstrated that the cells can turn light into electrical or chemical energy yet. But they hope to do soon.