Abstract
SummaryIron (Fe) and zinc (Zn) deficiencies are a global human health problem that may worsen by the growth of crops at elevated atmospheric CO 2 concentration (eCO 2). However, climate change will also involve higher temperature, but it is unclear how the combined effect of eCO 2 and higher temperature will affect the nutritional quality of food crops. To begin to address this question, we grew soybean (Glycine max) in a Temperature by Free‐Air CO 2 Enrichment (T‐FACE) experiment in 2014 and 2015 under ambient (400 μmol mol−1) and elevated (600 μmol mol−1) CO 2 concentrations, and under ambient and elevated temperatures (+2.7°C day and +3.4°C at night). In our study, eCO 2 significantly decreased Fe concentration in soybean seeds in both seasons (−8.7 and −7.7%) and Zn concentration in one season (−8.9%), while higher temperature (at ambient CO 2 concentration) had the opposite effect. The combination of eCO 2 with elevated temperature generally restored seed Fe and Zn concentrations to levels obtained under ambient CO 2 and temperature conditions, suggesting that the potential threat to human nutrition by increasing CO 2 concentration may not be realized. In general, seed Fe concentration was negatively correlated with yield, suggesting inherent limitations to increasing seed Fe. In addition, we confirm our previous report that the concentration of seed storage products and several minerals varies with node position at which the seeds developed. Overall, these results demonstrate the complexity of predicting climate change effects on food and nutritional security when various environmental parameters change in an interactive manner.
Highlights
Atmospheric CO2 is increasing and projected to reach between 730 and 1020 μmol mol-1 by the end of the century (Collins et al, 2013)
The results suggest that elevated atmospheric CO2 concentration (eCO2) in combination with elevated temperature may reduce seed yield relative to eCO2 conditions but will safeguard the mineral nutrition quality of soybeans
Soybean plants were grown in the field under conditions of eCO2 and elevated temperature similar to predicted conditions in 2050
Summary
Atmospheric CO2 is increasing and projected to reach between 730 and 1020 μmol mol-1 by the end of the century (Collins et al, 2013). Biomass production and seed yield are increased but often to a lesser extent than the increase in light-saturated photosynthesis (Long et al, 2004, Leakey et al, 2009). In addition to increasing yield, eCO2 has the potential to reduce the concentration of minerals in seeds and thereby threaten human nutrition, as highlighted in two recent meta-analysis studies. Across a range of C3 plants, Loladze (Loladze, 2014) reported that eCO2 reduced the concentrations of several minerals in foliar and edible tissues by approximately 8%, with the exception of Mn that was not reduced. The patterns of mineral changes were similar between foliar and edible tissue with the exception that
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