Sreeharsha, R.V., Mudalkar, S.,
Sengupta, D., Unnikrishnan, D.K.
and Reddy, A.R.
2019
"Mitigation of drought-induced
oxidative damage by enhanced
carbon assimilation and an
efficient anti-oxidative metabolism
under high CO2 environment
in pigeonpea (Cajanus cajan L.)."
Photosynthesis Research 139: 425-439.
NOTE:
Pigeonpea, usually spelled
Pigeon Pea, is something
I've eaten at local Indian
restaurants, and always
thought they were soybeans !
Sreeharsha et al. (2019) note
that pigeonpea (Cajanus cajan)
is “the main protein source
for more than a billion people
in the developing world
and a cash crop that supports
the livelihoods of millions
of resource-poor farmers
globally.”
So this experiment is
“highly relevant to understand
the impact of climate change
on this promising food crop.”
SUMMARY:
The authors conclude:
“the enhanced carbon
supply under elevated CO2
favored better growth
in pigeonpea under drought
stress associated with
effective sink capacity
in the form of nodules
mediating better
nitrogen assimilation.”
Sreeharsha et al. say their
results demonstrate
“a coordinated and integrated
mechanism in pigeonpea
to cope with drought stress
by taking advantage
of elevated CO2,”
whereby that
“enhanced antioxidative s
ystems ultimately [provide]
stress tolerance in
elevated CO2 grown
pigeonpea which [gains]
comparative advantage
in growth and metabolism
over ambient grown plants.”
Sreeharsha et al. report that
“elevated CO2 plants showed
35% higher photosynthesis rates
than ambient CO2 grown plants
at severe drought stress”
(9 days after stress initiation),
adding that
“elevated CO2 grown plants
recovered their photosynthesis
rates to 100% of their well-watered
counterparts, whereas
ambient CO2 grown plants
recovered to 85%.
DETAILS:
The five Indian researchers
grew pigeonpea for two
growing seasons at the
University of Hyderabad
(Hyderabad, Telangana State, India)
in open-top chambers under
ambient (390 ppm) or
elevated (600 ppm) CO2.
After 60 days,
Sreeharsha et al.
instituted drought stress
in half of the plants
in each CO2 treatment
by withholding water
for nine days,
followed by
a re-watering
to normal levels
immediately thereafter.
During and after
the drought stress period
the researchers conducted
a series of measurements
to determine various
physiological responses
of the crops under
the two CO2 treatments.
Under well-watered conditions,
elevated CO2 increased plant
photosynthesis by 64%,
nodule number by 38%
and nodule mass by 64%.
Photosynthesis and nodule mass
were also significantly higher
under elevated CO2
during drought stress
and the recovery period
thereafter.
Sreeharsha et al.
noted differences
among antioxidant levels
in the plants growing in
elevated CO2 under
both well-watered
and water-stressed
conditions.
Significant
antioxidant
up-regulation
under drought
at elevated
CO2 revealed
a CO2-induced
protective
mechanism
that helped guard
the plants against
oxidative damage
caused by reactive
oxygen species.