Effects on nutrients and on grain quality in spring wheat crops grown under elevated CO2 concentrations and stress conditions in the European, multiple-site experiment ‘ESPACE-wheat’

Abstract

Nutrient element concentrations and grain quality were assessed in spring wheat grown under elevated CO 2 concentrations and contrasting levels of tropospheric ozone at different nitrogen supply rates at several European sites. Carbon dioxide enrichment proved to affect nutrient concentrations in a complex manner. In green leaves, all elements (with exception of phosphorus and iron) decreased. In contrast, effects on the element composition of grains were restricted to reductions in nitrogen, calcium, sulphur and iron. Ozone exposure resulted in no significant effects on nutrient element concentrations in different tissues in the overall analysis. The nitrogen demand of green tissues was reduced due to CO 2 enrichment as shown by reductions in the critical leaf nitrogen concentration and also enhanced nitrogen use efficiency. Reductions in the content of ribulose-bisphosphate carboxylase/oxygenase and repression of the photorespiratory pathway and reduced nitrogen allocation to enzymes driving the photosynthetic carbon oxidation cycle were chiefly responsible for this effect. Thus, nitrogen acquisition by the crop did not match carbon acquisition under CO 2 enrichment. Since crop nitrogen uptake from the soil was already completed at anthesis, nitrogen allocated to the grain after anthesis originated from vegetative pools-causing grain nitrogen concentrations to decrease under CO 2 enrichment (on average by 15% when CO 2 concentrations increased from 360 to 680 mmol mol−1). Correspondingly, grain quality was reduced by CO 2 enrichment. The Zeleny value, Hagberg value and dry/wet gluten content decreased significantly with increasing [CO 2 ]. Despite the beneficial impact of CO 2 enrichment on growth and yield of C 3 cereal crops, declines in flour quality due to reduced nitrogen content are likely in a future, [CO 2 ]-rich world.

Effects of elevated O3 exposure on seed yield, N concentration and photosynthesis of nine soybean cultivars (Glycine max (L.) Merr.) in Northeast China

“…It suggests that the cumulative effects of E-O 3 on plant N metabolism might be much complicated in some key processes, e.g. the N pool size stored in vegetative tissues, which appears to determine the amount of available N during seed filling [17].…”

“…Therefore, the variation of leaf N status over time is essential to understand the underlying mechanism in crop yield loss and photosynthetic processes after exposure to elevated O 3 . Existing results demonstrated that elevated O 3 increased foliar N level in fen species [14], significantly decreased nitrate reductase activity in rice leaves [15], but had no significant effects on nutrient element concentrations in different tissues in wheat [16,17]. For soybean, the negative effects of O 3 on primary carbon metabolism have been well investigated, as indicated by stimulated aging and senescence, decreased photosynthesis and leaf chlorophyll content, impeded electron transport in the light reaction before senescence [18,19], a shorter development stage for carbon fixation [20] and relatively longer time for stomatal closure [21].…”

Cassava: The Drought, War and Famine Crop in a Changing World

“…The impacts of changes in CO 2 concentrations on micronutrients, especially those implicated in "hidden hunger" [42], in food plants also need to be considered. Trends are emerging that decreases in micronutrients such as iron and zinc may occur in the grains of rice and wheat in response to elevated CO 2 , although this is not always the case [204][205][206][207]. Again, these issues have received relatively little attention (compared to yields) in the context of the nutritional aspects of achieving food security.…”

Influence of free‐air CO2 enrichment (FACE) on the eating quality of rice

“…In wheat the reduced contents of protein in the grains, including gluten, decreased the quality of the flour and hence, the volume of bread loaves as a result of exposure to high CO 2 concentration in chambers 10 and in FACE treatments. 11 Rice grains produced under elevated CO 2 in chambers exhibited lower mineral and protein contents, while amylose content was higher than in those grown under ambient CO 2 .…”