Effects of elevated CO₂ on the protein concentration of food crops: a meta‐analysis

Abstract

Meta-analysis techniques were used to examine the effect of elevated atmospheric carbon dioxide [CO 2 ] on the protein concentrations of major food crops, incorporating 228 experimental observations on barley, rice, wheat, soybean and potato. Each crop had lower protein concentrations when grown at elevated (540-958 lmol mol À1 ) compared with ambient (315-400 lmol mol À1 ) CO 2 . For wheat, barley and rice, the reduction in grain protein concentration was $ 10-15% of the value at ambient CO 2 . For potato, the reduction in tuber protein concentration was 14%. For soybean, there was a much smaller, although statistically significant reduction of protein concentration of 1.4%. The magnitude of the CO 2 effect on wheat grains was smaller under high soil N conditions than under low soil N. Protein concentrations in potato tubers were reduced more for plants grown at high than at low concentrations of ozone. For soybean, the ozone effect was the reverse, as elevated CO 2 increased the protein concentration of soybean grown at high ozone concentrations. The magnitude of the CO 2 effect also varied depending on experimental methodology. For both wheat and soybean, studies performed in opentop chambers produced a larger CO 2 effect than those performed using other types of experimental facilities. There was also indication of a possible pot artifact as, for both wheat and soybean, studies performed in open-top chambers showed a significantly greater CO 2 effect when plants were rooted in pots rather than in the ground. Studies on wheat also showed a greater CO 2 effect when protein concentration was measured in whole grains rather than flour. While the magnitude of the effect of elevated CO 2 varied depending on the experimental procedures, a reduction in protein concentration was consistently found for most crops. These findings suggest that the increasing CO 2 concentrations of the 21st century are likely to decrease the protein concentration of many human plant foods.

Will Elevated Carbon Dioxide Concentration Amplify the Benefits of Nitrogen Fixation in Legumes?

“…3). In soybean, growth at elevated [CO 2 ] significantly decreased protein content, but only by 1.4% (Taub et al, 2008). Averaging the effects of elevated [CO 2 ] on wild and domestic legumes, there was no effect on seed N (Jablonski et al, 2002).…”

“…Will elevated [CO 2 ] affect legume seed quality to a similar extent? The evidence reported in two meta-analyses suggests that seed protein and N content will not be as affected by elevated [CO 2 ] in legumes as nonlegumes (Jablonski et al, 2002;Taub et al, 2008; Fig. 3).…”

“…Protein content of nonleguminous C 3 grains including barley (Hordeum vulgare), wheat (Triticum aestivum), and rice (Oryza sativa) declined by 14% at elevated [CO 2 ] (Taub et al, 2008), and concentrations of calcium, sulfur, iron, and zinc were also significantly lower in wheat grain (Loladze, 2002). Will elevated [CO 2 ] affect legume seed quality to a similar extent?…”

Assessing the impacts of current and future concentrations of surface ozone on crop yield with meta-analysis

“…Heterogeneity among levels of these categorical variables was assessed by re-sampling following Adams et al (1997). For multiple comparisons, groups were considered to differ significantly if their 95% confidence intervals did not overlap, providing a conservative test of group differences (Feng et al, 2008;Grantz et al, 2006;Morgan et al, 2003;Taub et al, 2008). Each categorical level for all crops was included in this analysis if there were at least two papers and five observations.…”

Impact of Elevated Atmospheric Carbon Dioxide on Yield, Vitamin C, Proximate, Fatty Acid and Amino Acid Composition of Capsicum (Capsicum Annuum)

“…Nutritional quality of capsicum was negatively affected by enhanced CO 2 , in terms of protein content. No such reduction in protein has been previously reported for capsicum, however it was observed for a number of other food plants like potato, rice and soybean [19,20]. This reduction could be a result of increased amount of nonstructural carbohydrates due to increased photosynthesis leading to dilution as well as increased water use efficiency.…”