Dong, J., Gruda, N., Lam,
S.K., Li, X. and Duan, Z.
2018
"Effects of elevated CO2 on
nutritional quality of vegetables:
A review."
Frontiers in Plant Science 9:
Article 924,
doi: 10.3389/fpls.2018.00924.
Dong et al. (2018) say
"a comprehensive review
of recent studies explaining
and targeting the key role of the
effect of elevated CO2 on
vegetable quality is lacking."
SUMMARY:
CO2-induced plant nutritional enhancements
far outweigh any CO2-induced plant nutritional
declines.
Future rising atmospheric CO2 concentrations
will bring future health benefits to human and
animal plant consumers.
DETAILS:
The team of five researchers
performed a meta-analysis
of 57 existing studies.
The 57 published works included
CO2 enrichment studies on
root vegetables
(carrot, radish, sugar beet and turnip),
stem vegetables
(broccoli, celery celtuce, Chinese kale,
ginger, onion, potato and scallion),
leafy vegetables
(cabbage, Chinese cabbage,
chives, fenugreek, Hongfengcat,
lettuce, oily sowthistle, palak
and spinach) and
fruit vegetables
(cucumber, hot pepper,
strawberry, sweet pepper
and tomato).
They examined
measurements
of nutritional quality,
including soluble sugars,
organic acids, protein,
nitrates, antioxidants
and minerals.
A CO2-induced stimulation
of soluble sugar accumulation
in the edible parts of vegetables
-- elevated CO2 "increased the
concentrations of fructose,
glucose, total soluble sugar,
total antioxidant capacity,
total phenols, total flavonoids,
ascorbic acid, and calcium
in the edible part of vegetables
by 14.2%, 13.2%, 17.5%,
59.0%, 8.9% 45.5%, 9.5%,
and 8.2%, respectively,
but decreased
the concentrations
of protein, nitrate,
magnesium, iron,
and zinc by 9.5%,
18.0%, 9.2%,
16.0%, and 9.4%.
Concentrations of titratable acidity,
total chlorophyll, carotenoids, lycopene,
anthocyanins, phosphorus, potassium,
sulfur, copper, and manganese
were not affected.
Dong et al. say that
"overall, elevated CO2
promotes the accumulation of
antioxidants in vegetables,
thus improving
vegetable quality,"
while adding that
"the CO2-induced stimulation of
total antioxidant capacity, total phenols,
total flavonoids, ascorbic acid, and
chlorophyll b indicate an improvement
of beneficial compounds in vegetables."
Decreases in protein, nitrate,
magnesium, iron, and zinc
were also observed in the
meta-analysis.
Those slight declines can be reduced,
if not reversed, by several approaches
that were investigated and discussed
by the authors, including:
"(1)
selecting vegetable species or cultivars
that possess greater ability in carbon fixation
and synthesis of required quality-related
compounds;
(2)
optimizing other environmental factors
(e.g., moderate CO2 concentrations,
moderate light intensity,
increased N availability,
or increased fertilization of Fe or Zn)
to promote carbon fixation and
nutrient uptake interactively
when growing plants under elevated CO2;
(3)
harvesting vegetable products earlier
in cases of over maturity and reduced
benefit of elevated CO2
to vegetative growth; and
(4)
combining elevated CO2
with mild environmental stress
(e.g., ultraviolet-B radiation
or salinity) in instances
when this enhances
vegetable quality
and might counteract
the dilution effect
or direct metabolic pathways
toward the synthesis of
health-beneficial compounds."
