Uddin, S., Parvin, S.,
Löw, M., Fitzgerald, G.J.,
Tausz-Posch, S.,
Armstrong, R.
and Tausz, M.
2019
Water use dynamics
of dryland canola
(Brassica napus L.)
grown on contrasting
soils under elevated CO2.
Plant and Soil 438: 205-222.
NOTE:
Canola
"currently ranks second
in terms of global importance
as a protein source for
livestock and third
for vegetable oil."
Uddin et al. (2019) write that
"it is essential to understand
the mechanisms underpinning
crop responses to future climates
to ensure future crop production."
This is particularly
important for
arid regions
where crop yields
are limited by
water shortage.
The goal of the
seven researchers
was to investigate
the impact of
elevated CO2
on the growth and
water use efficiency
of two canola
(Brassica napus)
cultivars in a dry-land
agro-ecosystem.
SUMMARY:
Uddin et al. report that
elevated CO2 increased
net photosynthesis by +14%
and reduced stomatal
conductance by 17%,
which resulted in a +37%
increase in plant water use
efficiency.
The authors conclude:
"lower water use
observed under
elevated CO2
may lead to higher
water content within
the soil profile
during the growing
season,"
while adding that
"water savings
under elevated CO2
may help to overcome
a major constraint
(susceptibility to drought)
limiting the expansion
of current Australian
canola production."
CO2 enrichment
also caused
greater plant leaf area,
a taller plant, increased
siliquae production and
a greater number of
sound seeds
per siliquae.
The end result
was an average
+20% increase
in seed yield
compared to
ambient CO2
grown plants,
averaged across
both cultivars
and soil types.
DETAILS:
The work was done
at the Australian Grains
Free-air CO2 Enrichment
(AGFACE) facility
in Horsham, Victoria,
Australia in the
winter season of 2015.
The two cultivars were
grown in large intact
soil cores comprised of
two different soil types
common to the
dryland region
that were subjected
to either ambient
(~400 ppm)
or elevated
(~550 ppm) CO2
during daylight hours
for the length of the
growing season.
Uddin et al. also observed
"despite greater leaf area,
water use in the present study,
measured using two different
but complementary techniques,
was lower under elevated CO2
than ambient CO2."
There was
"no evidence that stimulation
of leaf growth offset greater
leaf-level water use efficiency,
[therefore] water use
was decreased [by about 7%]
under elevated CO2
under the environmental
conditions of the current study."