Köhler, I.H., Huber, S.C.,
Bernacchi, C.J. and
Baxter, I.R.
2019
Increased temperatures
may safeguard the
nutritional quality of crops
under future elevated
CO2 concentrations.
The Plant Journal 97: 872-886.
NOTE:
Köhler et al. (2019) wrote:
"there is little information
about the impact
of elevated CO2
in combination with
elevated temperature
on seed mineral
concentrations."
The four scientists set out
"to determine the individual
and combined effect
of elevated CO2
and elevated temperature
on soybean seed composition
in terms of storage products
(protein and oil)
and important minerals."
SUMMARY:
Only one of the 20 mineral
elements examined (Fe)
showed a negative response
to elevated CO2 in both
growing seasons.
But with an increase
in temperature,
the CO2-induced decline
in Fe concentration
was completely offset.
Köhler et al. conclude that
"the potential threat
to human nutrition
by increasing CO2
concentration
(frequently made
by climate alarmists)
may not be realized."
Their results
"demonstrate the
complexity of
predicting climate
change effects
on food and
nutritional security
when various
environmental
parameters change
in an interactive
manner."
Changes in seed
mineral concentration
due to elevated CO2
and temperature
were mixed.
Elevated temperature
restored the small
reduction of mineral
concentrations
from elevated CO2,
back to the levels
obtained under
ambient CO2
and temperature
conditions.
DETAILS:
Köhler et al.
subjected soybean
(Glycine max, cv. Thorne)
plants to either 400 or
600 ppm CO2 and
ambient or elevated
temperatures that were
2.7/3.4 °C (day/night)
warmer than ambient,
being warmed
by infrared heaters.
The experiment
was conducted
in a Free-Air CO2
Enrichment (FACE)
facility (SoyFACE) near
Urbana Champaign,
Illinois, USA during
the 2014 and 2015
growing seasons.
The relative yield increase
due to elevated CO2
in the elevated temperature
treatments was greater
under the temperature
stressed conditions
than when temperatures
were unstressed, with a
+23% and +33% change
in 2014 and 2015.
Köhler et al. report that
"there was no significant
effect of elevated CO2
on protein or oil,"
whereas temperature
induced a slight reduction
in protein content
(less than 2% in 2014
and less than 1% in 2015),
but significantly increased
soybean seed oil
by about 1% in both
growing seasons.
Temperature stress
reduced yields
in both years
by 27% and 36%.
For the out 20 minerals
examined, only six were
significantly influenced
by elevated CO2
(B, Ca, Fe, K, S, Zn).
Of the six, only Fe had
a significant effect
in both growing seasons
(an 8% decline).
The rest were only
significant in one
of the two years
of study and all
experienced
slight declines
(less than 10%),
with the exception
of potassium, which
increased by 3%.
Elevated temperature
significantly impacted
the concentration of 14
of the 20 minerals,
increasing them
in nearly all instances
by up to 18%.
