Newswise, November 9, 2015 — With
the world population expected to reach 9 billion by 2050, engineers and
scientists are looking for ways to meet the increasing demand for food without
also increasing the strain on natural resources, such as water and energy — an
initiative known as the food-water-energy nexus.
Ramesh
Raliya, PhD, a postdoctoral researcher, and Pratim Biswas, PhD, the Lucy &
Stanley Lopata Professor and chair of the Department of Energy, Environmental
& Chemical Engineering, both at the School of Engineering & Applied
Science at Washington University in St. Louis, are addressing this issue by
using nanoparticles to boost the nutrient content and growth of tomato plants.
Taking
a clue from their work with solar cells, the team found that by using zinc
oxide and titanium dioxide nanoparticles, the tomato plants better absorbed
light and minerals, and the fruit had higher antioxidant content.
"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."
Zinc
is an essential nutrient for plants, helps other enzymes function properly and
is an ingredient in conventional fertilizer. Titanium is not an essential
nutrient for plants, Raliya says, but boosts light absorption by increasing
chlorophyll content in the leaves and promotes photosynthesis, properties
Biswas' lab discovered while creating solar cells.
The
team used a very fine spray using novel aerosolization techniques to directly
deposit the nanoparticles on the leaves of the plants for maximum uptake.
"We
found that our aerosol technique resulted in much greater uptake of nutrients
by the plant in comparison to application of the nanoparticles to soil,"
Raliya says.
"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. In both of the latter cases, the
nutrients are unavailable to plants."
Overall,
plants treated with the nanoparticles via aerosol routes produced nearly 82 percent
(by weight) more fruit than untreated plants. In addition, the tomatoes from
treated plant showed an increase in lycopene, an antioxidant linked to reduced
risk of cancer, heart disease and age-related eye disorders, of between 80
percent and 113 percent.
Previous
studies by other researchers have shown that increasing the use of
nanotechnology in agriculture in densely populated countries such as India and
China has made an impact on reducing malnutrition and child mortality. These
tomatoes will help address malnutrition, Raliya says, because they allow people
to get more nutrients from tomatoes than those conventionally grown.
In
the study, published online last month in the journal Metallomics, the team
found that the nanoparticles in the plants and the tomatoes were well below the
USDA limit and considerably lower than what is used in conventional fertilizer.
However,
they still have to be cautious and select the best concentration of
nanoparticles to use for maximum benefit, Biswas says.
Raliya
and the rest of the team are now working to develop a new formulation of
nanonutrients that includes all 17 elements required by plants.
"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."
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