When it comes to water, some plants are picky drinkers.
For example, grapes grown for the premium cabernet and merlot
varieties require very precise amount of water to produce fruit of just
the right sweetness. But modern measurements of plant water levels are
far from ideal, says Alan Lakso, a professor at Cornell University
who has been studying plant physiology for 40 years. Most commercial
methods measure water levels by placing moisture readers in soil. But
grapevine and apple tree roots like to travel — they can sprawl far from
the reader location and skew the picture.
“They all measure water in the soil which is sort of indirect,
because you’re not harvesting the soil,” Lakso says. “You are harvesting
the plant.”
Measuring water levels inside the plant itself is a more accurate way
to do it, but it’s a manual, labor-intensive process. Measurers cut off
a leaf, place it into a pressure chamber and apply pressure to it until
water comes out of the severed trimming. Because the method is
time-consuming and slow, growers don’t use it often. Neither does it
provide a continuous picture of the plant’s health, Lakso says, likening
the process to taking a blood pressure on a patient once a week. “It
tells you what it is, but it doesn’t tell what it was the week before,”
Lakso says. “I wanted to have a way of monitoring plants continuously.”
So he went inside the plant, “Fantastic Voyage” style.
To measure plant water levels continuously, every plant has to be
equipped with its own personal water sensor — and that’s exactly what
the Cornell team went for. Lakso and Abraham Stroock, associate professor of chemical and biomolecular engineering, as well as Vinay Pagay,
a Ph.D student at the time, created an electronic microchip water
sensor that can be inserted right into the plant. In building the chip,
they used the plants’ very own architecture for water management, basing
the design on plant physiology.
Plant leaves have tiny pores filled with water brought up from the
roots; that water evaporates through the leaves’ membranes. The chip
also has a cavity filled with water and a membrane through which water
evaporates. As the plant’s water depletes, so does the sensor’s. When
the level dips, the chip sends a signal to a data logger via a wire or a
wireless transmitter to be interpreted and stored. The farmer is tipped
off that it’s time to water the plants. When crops are quenched, the
chip will replenish its moisture, too, and the cycle will begin anew.
The chips, which researches estimate can be mass-produced for about US
$5 each, will allow growers to dynamically adjust their irrigation
schedules to various weather flukes that affect water evaporation in
plants.
“The water state of a plant changes with the weather,” says Lakso,
adding that clouds, dry hot air, and wind can cause rapid changes. The
chips will allow growers to take quick readings and follow up with quick
actions.
The technology is of a particular interest to wineries because red
grapes benefit from slight water shortage later in the season, says
Pagay, who studied viticulture and pomology—the sciences of growing
grapes and fruit.
“A plant that has too much water tends to put more energy into the
leaves,” he explains. “We are trying to make it put more energy into the
grapes.” That’s why a little bit of “water stress” leads to better
tastier fruit. “The grapes come out sweeter,” Pagay says. “Varieties
like the Napa Valley cabernet and merlot are made from grapes that
typically have some amount of water stress.”
Pagay says the chips will soon start their testing rounds with Ernest & Julio Gallo Winery
of Modesto, California. But the technology has a much broader use than
just the wine industry. As the U.S. and other parts of the world labor
under a record-breaking drought, the team hopes that their invention can
help farmers who are coping with serious water shortages, or work in
dry climate areas.
The chips will tell the growers whether they need to irrigate or not,
thus preventing unnecessary water use. About 70 percent of humans’
water consumption is used for agriculture, so optimizing irrigation is a
big issue, says Lakso.
“We certainly hope and expect the sensor to help optimize irrigation and water use.”
Source
by Lina Zeldovich, Modern Farmer