Pan, C.,
Ahammed, G.J.,
Li, X. and Shi, K.
2018
Elevated CO2 improves
photosynthesis under
high temperature
by attenuating the
functional limitations
to energy fluxes,
electron transport
and redox homeostasis
in tomato leaves.
Frontiers in Plant Science 9:
Article 1739,
doi: 10.3389/fpls.2018.01739.
NOTE:
Heat stress can cause
plant dehydration and
oxidation damage
to bio-membranes,
from elevated reactive
oxygen species ( ROS ).
Elevated CO2 levels
reduce the severity
of this heat stress.
Interactive effects
of heat stress and
atmospheric CO2
on plants were
investigated by
Pan et al. (2018).
SUMMARY:
Pan et al. write that the
"heat stress-caused
drastic reduction
in CO2 assimilation."
Elevated CO2
was able to
fully reverse
the negative effects
of heat stress
on net photosynthesis
of the tomato plants.
Figure 1, below:
Effects of
elevated CO2
and heat stress
on the net
photosynthetic
rate ( Pn )
of tomato plants.
The red text above
shows the change in Pn
due to elevated CO2
during the control,
heat and recovery
stages.
At normal
temperatures,
elevated CO2
increased net
photosynthesis
by +45%.
Regardless of CO2
concentration, heat stress
reduced net photosynthesis,
which parameter increased
during the recovery period
but not quite back to its
pre-stressed condition.
Nevertheless,
elevated CO2 caused
a relative increase
in net photosynthesis
of +116% and +96%
during heat stress
and recovery.
Figure 2, below
presents the effects
of elevated CO2
and heat stress
on the maximum
photochemical
efficiency of
photosystem II
( Fv / Fm )
The left panel
displays
the maximum
photochemical
efficiency
of photosystem II
( Fv / Fm )
shown in pseudo
color images,
The right panel
shows the actual
Fv/Fm values,
with the
percentages
in red text,
indicating
the change
in Fv/Fm values,
due to
elevated CO2
during the heat
and recovery
period.
Elevated CO2
had no effect
on Fv / Fm
under normal
temperature
conditions.
But it increased
this parameter
by +60%
and +14%
in response
to heat stress
and at recovery,
respectively,
compared with
that observed
in the ambient
CO2 treatments.
DETAILS:
Work was conducted
in environmentally
controlled growth
chambers
( E8 Growth Chamber,
Conviron, Winnipeg,
MB, Canada )
Tomato seedlings
( Solanum
lycopersicum
cv. Hezuo 903 )
were exposed to
CO2 concentrations
of either 380 ppm,
or 800 ppm.
After an acclimation
period of 48 hours,
half the seedlings
in each
CO2 treatment,
were subjected
to 24 hours
of heat stress
( 42°C, compared
to unstressed
day / night t
emperatures
of 26/22°C
in control plants ),
followed by
a 24 hour
recovery
period.
After 24 hours
of heat stress
and again
after the 24 hour
recovery period
back to the control
temperatures,
measurements
were made
to evaluate
the ability
of elevated CO2
to mitigate
temperature
stress.