Fans of The Simpsons may recall Lisa using genetic engineering to create a super tomato that she hoped would cure world hunger. Now researchers at Washington University in St. Louis (WUSTL) have come close to the real thing, not through genetic engineering, but with the use of nanoparticles. Although the individual fruit aren't as large as Lisa's creation, the team's approach has resulted in tomato plants that produced almost 82 percent more fruit by weight, with the fruit also boasting higher antioxidant content.

The new technique developed by Ramesh Raliya, PhD and Pratim Biswas, PhD, both at WUSTL's School of Engineering & Applied Science, involves the use of zinc oxide and titanium dioxide nanoparticles to boost the tomato plant's ability to absorb light and minerals. The titanium oxide increases chlorophyll content in the plant's leaves to improve photosynthesis, while zinc is an essential nutrient that also helps the function of enzymes within the plant.

"When a plant grows, it signals the soil that it needs nutrients," Biswas says. "The nutrient it needs is not in a form that the plant can take right away, so it secretes enzymes, which react with the soil and trigger bacterial microbes to turn the nutrients into a form that the plant can use. We're trying to aid this pathway by adding nanoparticles."

The team found that directly depositing the nanoparticles on the plant's leaves as a very fine spray resulted in a much greater uptake of nutrients than if the nanoparticles were applied to the soil.

"A plant can only uptake about 20 percent of the nutrients applied through soil, with the remainder either forming stable complexes with soil constituents or being washed away with water, causing runoff," says Raliya. "In both of the latter cases, the nutrients are unavailable to plants."

In addition to the plants treated with the aerosol nanoparticles producing almost 82 percent more fruit by weight than untreated plants, the tomatoes themselves had an increase of between 80 and 113 percent in levels of lycopene. This is an antioxidant that gives tomatoes and some other red fruits and vegetables their red color and has been the subject of numerous studies seeking to ascertain a link between it and a reduced risk of cancer – none of which have been conclusive according to the FDA.

Biswas says that the optimal concentration of nanoparticles that provide the maximum benefit still needs to be determined, but the plants and tomatoes used in the study had nanoparticle levels well below the USDA limit and were considerably lower than those found in conventional fertilizer.

The team is now developing a new formulation of nanonutrients that doesn't just include zinc, but all 17 elements plants require to grow. They hope such a technique could help feed the 9 billion people that are expected to inhabit the planet by 2050, without placing extra strain on water and energy resources.

"In 100 years, there will be more cities and less farmland, but we will need more food," Raliya says. "At the same time, water will be limited because of climate change. We need an efficient methodology and a controlled environment in which plants can grow."

The research appears in the journal Metallomics.

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