Zheng, Y.P., Li, R.Q., Guo, L.L.,
Hao, L.H., Zhou, H.R., Li, F.,
Peng, Z.P., Cheng, D.J. and Xu, M.
2018
"Temperature responses of photosynthesis
and respiration
of maize (Zea mays)
plants to experimental warming."
of maize (Zea mays)
plants to experimental warming."
Russian Journal of Plant Physiology 65: 524-531.
NOTE:
A concerns about global warming
is that rising temperatures
will reduce crop yields.
This assumption is mainly based
on plant net photosynthesis
measurements across a range
of temperature values.
Such data generally depict
an inverted u-shaped curve,
where photosynthesis rises
as temperatures warm,
then peaks at an optimum
temperature value, after which
it declines towards zero
as temperatures
continue to rise.
SUMMARY:
Zheng et al. conclude
that in response to warming,
maize plants experienced
an apparent
"thermal acclimation
of the net photosynthetic rate
and leaf dark respiration,"
which
"may mitigate or even offset
the negative impacts on maize
from future climate warming."
The findings suggest
a warming climate
may produce higher
a warming climate
may produce higher
crop yields, which is
far different than
what climate alarmists
far different than
what climate alarmists
have been claiming.
Zheng et al. report that
experimental warming
"significantly enhanced
the maximum values of
net photosynthetic rate
(An) by about +60%
(P = 0.004)
from an average
of 18.6 µmol/(m2 s)
for plants grown
at ambient temperature
to 29.8 µmol/(m2 s)
for plants grown
at elevated temperature."
The authors note that the
optimal temperature
for plant photosynthesis (Topt)
in the elevated temperature
treatment also rose by 2°C
compared to that observed
in the ambient temperature
treatment (i.e., Topt rose
from 29.0 to 31.0°C).
DETAILS:
Working with maize plants
( Zea mays ),
the nine researchers conducted
a field experiment to examine
the crop's potential
for thermal acclimation.
They grew maize
at the Yucheng
Comprehensive
Comprehensive
Experiment Station
on the North China Plain,
an area of widespread
maize production,
under normal and elevated
temperature conditions.
Elevated temperature plots
were warmed by infrared radiators,
resulting in temperature conditions
for the air, soil and canopy
that were 1.42/1.77°C (day/night),
1.68/2.04°C (day/night)
and 2.08°C (day) higher
than the control temperature
treatment, respectively.
Sixty days after sowing,
the scientists conducted
several physiological and
biochemical measurements
on fully expanded ear leaves
at the heading stage
of the maize plants.
Leaf dark respiration rates
were consistently greater
in the ambient, as opposed to
the elevated temperature
treatment, but warming
helped improve leaf
carbohydrate levels,
where warming
"significantly enhanced
the concentration of
soluble sugars by
+43.7% (P < 0.01),"
starch concentrations
by +20% (P < 0.05)
and total nonstructural
carbohydrates
by +30.8% (P < 0.01).
