Bencke-Malato, M., De Souza, A.P.,
Ribeiro-Alves, M., Schmitz, J.F.,
Buckeridge, M.S. and Alves-Ferreira, M.
2019
"Short-term responses
of soybean roots to
individual and combinatorial
effects of elevated [CO2]
and water deficit."
Plant Science 280: 283-296.
NOTE:
Bencke-Malato et al. (2019),
say that soybean (Glycine max) is
"the most economically important
legume worldwide,"
and
"is widely used for human
and animal consumption
due to the high protein
and oil contents in its seeds
and serves as a source
for biodiesel production."
SUMMARY:
Bencke-Malato et al. report that,
prior to water deficit initiation,
elevated CO2 increased
photosynthesis by +103%,
which photosynthetic
improvement led to
increases in leaf, stem,
root and total biomass by
+49.3%, +61.6%, +37.9%
and +50%, respectively.
Elevated CO2 also
increased plant height
by +18% and leaf area
by +43%.
The researchers concluded:
"both physiological and
transcriptomic analyses
demonstrated that
elevated CO2 may mitigate
the negative effects
of water deficit
on soybean roots."
DETAILS:
The team of six scientists
wanted to understand the
physiological, biochemical,
and genetic responses
of soybean to rising
concentrations of
atmospheric CO2,
and possible changes
in climate, to develop
strategies for maintaining
and/or improving its yield
potential in the future.
Bencke-Malato et al.
investigated
the individual
and combined
effects of
elevated CO2 and
water deficit
on soybean growth.
Their work was conducted
on a drought-tolerant cultivar
(Embrapa 48),
which was grown
hydroponically under
controlled-environment
conditions in a greenhouse
at the University of São Paulo,
São Paulo, Brazil.
In the experiment,
half of the plants
were exposed
to ambient CO2
concentrations (400 ppm)
and half to elevated CO2
concentrations of 800 ppm
for 24 days
(until the V3/V4 stage).
Thereafter, a water deficit
treatment was applied
by removing plants out of
their hydroponic solution
and exposing their roots
to ambient or elevated CO2
air for 0, 25 or 50 minutes.
Various physiological
and gene expression
measurements were made
on the plants at each
of these three water deficit
time steps to evaluate
for any influence
of elevated CO2.
When water deficit
was applied,
net photosynthesis
under ambient CO2
declined by
approximately -46%
after 25 minutes
(relative to T0)
and -84% after 50 minutes
(again, relative to T0).
In contrast,
net photosynthesis
under elevated CO2
experienced no decline
(relative to T0)
after 25 and 50 minutes
of water deficit.
Bencke-Malato et al. note that
elevated CO2 induced a reduction
in stomatal conductance,
which they say led to
an increase in plant water
use efficiency that:
"promoted the maintenance
of photosynthetic rates
and fresh weight of leaves
... up to 25 min of water deficit,"
and which
"suggests that elevated CO2
buffers the adverse effects
of water deficit by maintaining
the water content in the plant."
With respect to genome-wide
expression profiling,
the authors identified
302 genes that were d
ifferentially expressed
in the soybean plant roots
grown under ambient
versus elevated CO2.
Of these differentially
expressed genes,
most (274) were
down-regulated
as opposed to
up-regulated (28).
In particular,
down-regulated genes
at elevated CO2
were generally related
to iron uptake
and transport,
antioxidant activity,
secondary metabolism
and defense
and stress response.
When plants were grown
under elevated CO2
and treated with
instantaneous
water deficiency,
Bencke-Malato et al.
found that elevated CO2
"reverted the expression
of water deficit-induced genes
related to stress,
defense, transport
and nutrient deficiency."
