By Susan Varlamoff
University of Georgia
By measuring the nighttime respiration rate of plants, University
of Georgia scientists hope to develop a way farmers can detect
environmental stresses in their fields.
Stresses like low soil moisture, high or low air temperatures,
weeds, insects and diseases can reduce plants’ growth, yields and
quality. They can hurt a plant before it shows any signs of
problems.
During the recent drought, the lack of rain greatly damaged
plants. Finding a way to know when soil moisture levels become
low before the damage occurs is an important reason for this
research.
Looking for a connection
“We’re essentially looking for a correlation between
environmental stress and high nighttime carbon dioxide
respiration rates,” said Anandakumar Karipot, an assistant
research scientist with the UGA College of Agricultural and
Environmental Sciences.
Karipot, professor Monique Leclerc and postdoctoral associate
Gengsheng Zhang are analyzing the data for this project in the
UGA Laboratory for Environmental Physics in Griffin, Ga. CAES
agronomist John Beasley and U.S. Department of Agriculture
physiologist Diane Rowland are also members of the research team.
Environmental stresses typically reduce the transpiration rate
and the amount of water vapor given off by plants. Lower
transpiration rates increase plant temperatures. They also
increase nighttime respiration rates that produce carbon dioxide.
Reduced growth, yield and quality
When the plant expends energy to respire faster, it can’t produce
as much food for itself (photosynthesis). This reduces its
growth, yield and quality.
“It’s similar to a human being: if you can’t prespire, your body
overheats and your respiration rate increases,” Beasley said.
“When a peanut plant is stressed, it can’t produce the pod or
fruit.”
The scientists are measuring carbon dioxide fluxes above a peanut
field at the UGA Southwest Georgia Research and Education Center
in Plains, Ga.
The sensors, known as an Eddy covariance system, include a fast-
response, sonic gauge that measures the wind speed in three
directions and an infrared gas analyzer that determines carbon
dioxide concentration fluctuations.
Together, these sensors provide information on plants’ uptake of
carbon dioxide emissions.
They also record supporting measurements of soil temperature,
soil water content and solar and earth radiation. The scientists
collect data from planting until harvest. That helps them study
variations in carbon dioxide fluxes and their relation to water
stress at different stages of plant growth.
Uniform fields work best
There is no photosynthesis at night. That’s when plants respire
and release carbon dioxide. So the variations in nighttime carbon
dioxide levels will indicate environmental stress.
“It’s important that the peanut field we chose for this study is
fairly large, flat and uniform with similar soil properties,”
Karipot said. “This ensures that similar conditions exist
throughout the field and the carbon dioxide variations are
representative of the peanut crop.”
A weather-monitoring station also measures wind speed and
direction, rainfall, air temperature and humidity and solar
radiation in the field. This information will help the scientists
understand the microclimatic influence on the plants’ growth and
yield. It will help them better interpret the carbon dioxide
respiration data.
“We would like to extend our research next year to two fields,”
Karipot said, “one with irrigation and one without irrigation,
and see the difference in respiration rates of the crops with and
without water stress.”
This research could be developed into a tool to warn farmers of
water stress in their fields and help them manage irrigation
better.
