BENEFITS OF ATMOSPHERIC CO2
ENRICHMENT ON STRAWBERRY
CO2SCIENCE & SPPI ORIGINAL PAPER ♦
February 5, 2015
BENEFITS OF ATMOSPHERIC CO2 ENRICHMENT ON STRAWBERRY
Citation: Center for the Study of Carbon Dioxide and Global Change. "Benefits of Atmospheric CO2 Enrichment on
Strawberry.” Last modified February 5, 2015. http://www.co2science.org/subject/a/summaries/agriculturestraw.php.
Nearly all agricultural plants benefit from increases in the air's CO2 content and strawberry
(Fragaria x ananassa) is no exception. The Plant Growth Database1 of CO2 Science, for
example, presents 30 individual experimental results from peer-reviewed studies, demonstrating
the fact that elevated CO2 enhances rates of photosynthesis and biomass production in this
important agricultural species (see
http://www.co2science.org/data/plant_growth/dry/f/fragariaa.php and
http://www.co2science.org/data/plant_growth/photo/f/fragariaa.php). In this summary we
highlight the work of some of these studies, plus other work that illustrates yet other important
benefits strawberries will reap as the air’s CO2 content rises in the years and decades to come.
We begin with the study of Deng and Woodward (1998)2, who grew strawberries in controlled
glasshouses exposed to atmospheric CO2 concentrations of 390 and 560 ppm for nearly three
months. In addition, the strawberries were supplied with fertilizers containing three levels of
nitrogen so that the pair of researchers could study the direct and interactive effects of elevated
CO2 and nitrogen supply on strawberry growth.
Results indicated that elevated CO2 increased
rates of net photosynthesis and total plant dry
weight at all nitrogen levels. In addition, the
extra CO2 provided enough sugar and physical
mass to support significantly greater numbers
of flowers and fruits than in the plants grown at
390 ppm CO2. This effect consequently led to
total fresh fruit weights that were 42 and 17%
greater in CO2-enriched plants that received the
highest and lowest nitrogen levels,
respectively. Further, elevated CO2 increased
the nitrogen-use efficiency of these plants by
23 and 17%, respectively.
Such findings suggest that, as the amount of
CO2 in the atmosphere increases, strawberry
plants will exhibit increased rates of
photosynthesis, regardless of soil nitrogen
fertility. Additionally, the increased supply of
carbohydrates provided by this phenomenon
will likely be utilized by the plants to increase
their size and numbers of flowers and fruits.
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As the amount of CO2 in the
atmosphere increases,
strawberry plants will exhibit
increased rates of
photosynthesis, regardless of
soil nitrogen fertility.
Additionally, the increased
supply of carbohydrates
provided by this phenomenon
will likely be utilized by the
plants to increase their size and
numbers of flowers and fruits.
http://www.co2science.org/data/plant_growth/plantgrowth.php
http://www.co2science.org/articles/V2/N11/B1.php
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Ultimately, these effects will lead to increased yields, which should be very important to
commercial strawberry growers and home gardeners.
Working in the field, Bunce (2001)3 grew strawberry plants in open-top chambers at three levels
of atmospheric CO2 (350, 650, and 950 ppm) over a period of two years in an effort to study the
effects of elevated CO2 on photosynthesis in this important agricultural crop. Measurements
were made on a weekly basis to evaluate the temperature dependence of photosynthetic
stimulation resulting from the two levels of atmospheric CO2 enrichment.
Surprisingly, elevated CO2 increased photosynthetic rates to an even greater extent than
predicted by kinetic models based on the characteristics of the enzyme rubisco at all
temperatures. Although photosynthetic acclimation was apparent in two-thirds of the
measurements made during the course of the experiment, plants grown at 650 and 950 ppm CO2
still exhibited average photosynthetic rates that were 77 and 106% greater, respectively, than
those displayed by control plants exposed to ambient air. In addition, when soil water potentials
were measured during several "dry summer days," as the author described them, an increasingly
greater amount of soil moisture was indicated for each step increase in the air's CO2
concentration. Thus, as the CO2 concentration of the atmosphere increases, strawberry plants
will likely exhibit enhanced rates of photosynthesis, regardless of seasonal air temperature,
which should lead to increased biomass and fruit production. In addition, strawberry plants
should fare better under conditions of water stress than they do now.
Bushway and Pritts (2002)4 studied the effects of atmospheric CO2 enrichment on the early
spring photosynthesis and growth of over-wintering strawberry plants. The plants were grown in
controlled environmental chambers receiving ambient (375 ppm) and elevated (700 to 1,000
ppm) atmospheric CO2 concentrations for about six weeks until new blooms began to form on
the plants, after which they were moved to a common greenhouse receiving ambient CO2
concentrations.
Elevated CO2 stimulated rates of photosynthesis in leaves of the over-wintering strawberry plants
by more than 50%. This phenomenon led to significantly greater amounts of starch in key plant
organs when new spring growth began. Indeed, plants grown in elevated CO2 had two-, threeand four-times the amount of starch in their crowns, leaves and roots, respectively, than their
ambiently-grown counterparts. In addition, plants grown in elevated CO2 flowered and fruited
an average of four and seven days earlier than plants grown in ambient air, respectively. Finally,
yield per plant was increased by 62% due to atmospheric CO2 enrichment.
Based upon these several findings, it would appear that over-wintering strawberry plants will
exhibit enhanced rates of photosynthesis and starch production as the air's CO2 content increases,
which will support more rapid and extensive growth in the spring. Such increases in
carbohydrate availability at this critical time should allow strawberry plants in a CO2-enriched
world to produce greater numbers of fruit per plant, thus increasing marketable berry yields.
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http://www.co2science.org/articles/V5/N2/B3.php
http://www.co2science.org/articles/V5/N21/B1.php
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Plants grown in air enriched
with an extra 300 ppm CO2
produced 17.6% more dry
matter per fruit than the
plants grown in ambient air,
while plants grown in air
enriched with an extra 600
ppm CO2 produced 38.5% more
Wang and Bunce (2004)5 grew strawberry plants outof-doors in open-top chambers maintained at three
different CO2 concentrations. The plants were grown
from rooted runners transplanted into field plots until
the plants reached maturity and their fruit were
harvested at the commercially ripe stage, after which
the fruit were analyzed for a number of parameters
that contribute to their flavor and aroma. In doing so
the authors determined that plants grown in air
enriched with an extra 300 ppm CO2 produced 17.6%
more dry matter per fruit than the plants grown in
ambient air, while plants grown in air enriched with
an extra 600 ppm CO2 produced 38.5% more dry
matter per fruit than the plants grown in ambient air.
Wang and Bunce also found that the ambient + 300
ppm CO2 plants contained 12% more total sugars
plants grown in ambient air. (which enhance flavor) per gram dry weight of fruit
than the ambient-treatment plants, while the ambient +
600 ppm plants contained 20% more total sugars per
gram dry weight of fruit than the ambient-treatment plants. In addition, the ambient + 300 ppm
CO2 plants contained 8.4% less total organic acids (which promote sourness) per gram dry
weight of fruit than the ambient-treatment plants, while the ambient +600 ppm plants contained
17.4% less total organic acids per gram dry weight of fruit than the ambient-treatment plants. It
was also observed that the elevated levels of atmospheric CO2 significantly increased the fruit
concentrations of several aroma-enhancing compounds, leaving the two scientists to conclude
their paper by saying "the results of this study indicate that enhancing CO2 concentration in the
growing atmosphere would probably improve fruit quality by increasing fruit dry weight, sugar
and aroma concentration and decreasing acid content."
dry matter per fruit than the
Probing into yet other benefits of atmospheric CO2 enrichment on strawberries, Wang et al.
(2003)6 evaluated the effects of elevated CO2 on strawberry fruit antioxidant activity and
flavonoid content. More specifically, the three scientists grew strawberry plants in open-top
chambers maintained at either ambient atmospheric CO2 concentration, ambient + 300 ppm CO2,
or ambient + 600 ppm CO2, for a period of 28 months, harvesting the fruit "at the commercially
ripe stage" and analyzing it for a number of different antioxidant properties and flavonol
contents.
Before reporting what they found, however, Wang et al. provide some background by noting that
"strawberries are good sources of natural antioxidants (Heinonen et al., 1998)." They further
report that "in addition to the usual nutrients, such as vitamins and minerals, strawberries are also
rich in anthocyanins, flavonoids, and phenolic acids," and that "strawberries have shown a
remarkably high scavenging activity toward chemically generated radicals, thus making them
effective in inhibiting oxidation of human low-density lipoproteins (Heinonen et al., 1998)." In
this regard, they note that previous studies (Wang and Jiao, 2000; Wang and Lin, 2000) "have
shown that strawberries have high oxygen radical absorbance activity against peroxyl radicals,
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http://www.co2science.org/articles/V7/N46/B1.php
http://www.co2science.org//articles/V6/N34/EDIT.php
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superoxide radicals, hydrogen peroxide, hydroxyl radicals, and singlet oxygen." In their
experiment, therefore, they were essentially seeking to see if atmospheric CO2 enrichment could
make a good thing even better.
In discussing their findings, the scientists report, first of all, that strawberries had higher
concentrations of ascorbic acid (AsA) and glutathione (GSH) "when grown under enriched CO2
environments." In going from ambient to +300 ppm and +600 ppm CO2, for example, AsA
concentrations increased by 10 and 13%, respectively, while GSH concentrations increased by 3
and 171%, respectively. They also learned that "an enriched CO2 environment resulted in an
increase in phenolic acid, flavonol, and anthocyanin contents of fruit." For nine different
flavonoids, for example, there was a mean concentration increase of 55 ± 23% in going from the
ambient atmospheric CO2 concentration to +300 ppm CO2, and a mean concentration increase of
112 ± 35% in going from ambient to +600 ppm CO2. In addition, they report that the "high
flavonol content was associated with high antioxidant activity." As for the significance of these
findings, Wang et al. note that "anthocyanins have been reported to help reduce damage caused
by free radical activity, such as low-density lipoprotein oxidation, platelet aggregation, and
endothelium-dependent vasodilation of arteries (Heinonen et al., 1998; Rice-Evans and Miller,
1996)."
In summarizing their findings, Wang et al. say "strawberry fruit contain flavonoids with potent
antioxidant properties, and under CO2 enrichment conditions, increased the[ir] AsA, GSH,
phenolic acid, flavonol, and anthocyanin concentrations," further noting that "plants grown under
CO2 enrichment conditions also had higher oxygen radical absorbance activity against [many
types of oxygen] radicals in the fruit." These findings, coupled with those of Wang and Zheng
(2001), which show that warmer temperatures (particularly warmer nighttime temperatures) also
enhance the phenolic content and antioxidant
activities in strawberries, bode well for
It is therefore a shame when
strawberry growth under model scenarios of
future climate and atmospheric CO2
government organizations
concentrations.
The results of the several studies presented
above are extremely encouraging. As the air's
CO2 content continues to rise, strawberry plants
will likely exhibit enhanced rates of
photosynthesis and biomass production, which
should lead to greater fruit yields in this
economically important agricultural crop. They
will also likely benefit in other ways, including
the production of more flowers and fruit that will
develop more quickly. Starch content,
phenolics, and antioxidants will all be enhanced
and strawberry plants will be better able to cope
with water stress, nitrogen stress, and the stress
of oxidation. And multiple reviews posted on
our CO2 Science website indicate these benefits
are realized in many, many other crops,
endowing humanity with a highly optimistic
future. It is therefore a shame when government
such as the United Nations
Intergovernmental Panel on
Climate Change or the U.S.
Environmental Protection
Agency fail to sufficiently
acknowledge such benefits and
instead forge ahead with
efforts that would mute them
when they should be
promoting them.
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organizations such as the United Nations Intergovernmental Panel on Climate Change or the
U.S. Environmental Protection Agency fail to sufficiently acknowledge such benefits and instead
forge ahead with efforts that would mute them when they should be promoting them.
REFERENCES
Bunce, J.A. 2001. Seasonal patterns of photosynthetic response and acclimation to elevated
carbon dioxide in field-grown strawberry. Photosynthesis Research 68: 237-245.
Bushway, L.J. and Pritts, M.P. 2002. Enhancing early spring microclimate to increase carbon
resources and productivity in June-bearing strawberry. Journal of the American Society for
Horticultural Science 127: 415-422.
Deng, X. and Woodward, F.I. 1998. The growth and yield responses of Fragaria ananassa to
elevated CO2 and N supply. Annals of Botany 81: 67-71.
Heinonen, I.M., Meyer, A.S. and Frankel, E.N. 1998. Antioxidant activity of berry phenolics on
human low-density lipoprotein and liposome oxidation. Journal of Agricultural and Food
Chemistry 46: 4107-4112.
Rice-Evans, C.A. and Miller, N.J. 1996. Antioxidant activities of flavonoids as bioactive
components of food. Biochemical Society Transactions 24: 790-795.
Wang, S.Y. and Bunce, J.A. 2004. Elevated carbon dioxide affects fruit flavor in field-grown
strawberries (Fragaria x ananassa Duch). Journal of the Science of Food and Agriculture 84:
1464-1468.
Wang, S.Y., Bunce, J.A. and Maas, J.L. 2003. Elevated carbon dioxide increases contents of
antioxidant compounds in field-grown strawberries. Journal of Agricultural and Food
Chemistry 51: 4315-4320.
Wang, S.Y. and Jiao, H. 2000. Scavenging capacity of berry crops on superoxide radicals,
hydrogen peroxide, hydroxyl radicals, and singlet oxygen. Journal of Agricultural and Food
Chemistry 48: 5677-5684.
Wang, S.Y. and Lin, H.S. 2000. Antioxidant activity in fruit and leaves of blackberry,
raspberry, and strawberry is affected by cultivar and maturity. Journal of Agricultural and Food
Chemistry 48: 140-146.
Wang, S.Y. and Zheng, W. 2001. Effect of plant growth temperature on antioxidant capacity in
strawberry. Journal of Agricultural and Food Chemistry 49: 4977-4982.
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www.co2science.org
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