Increased periods of water shortage and higher temperatures, together with a reduction in nutrient availability, have been proposed as major factors that negatively impact plant development. Photosynthetic CO2 assimilation is the basis of crop production for animal and human food, and for this reason, it has been selected as a primary target for crop phenotyping/breeding studies. Within this context, knowledge of the mechanisms involved in the response and acclimation of photosynthetic CO2 assimilation to multiple changing environmental conditions (including nutrients, water availability, and rising temperature) is a matter of great concern for the understanding of plant behavior under stress conditions, and for the development of new strategies and tools for enhancing plant growth in the future. The current review aims to analyze, from a multi-perspective approach (ranging across breeding, gas exchange, genomics, etc.) the impact of changing environmental conditions on the performance of the photosynthetic apparatus and, consequently, plant growth.

The availability and management of N are major determinants of crop productivity, but N excessive use has an associated agro-ecosystems environmental impact. The aim of this work was to investigate the influence of N fertilization on yield and grain quality of 6 durum wheat genotypes, selected from 20 genotypes as high- and low-yielding genotypes. Two N levels were applied from anthesis to maturity: high (½ Hoagland nutrient solution) and low (modified ½ Hoagland with one-third of N). Together with the agronomic characterization, grain quality analyses were assessed to characterize carbohydrates concentration, mineral composition, glutenin and gliadin concentrations, polyphenol profile, and anti-radical activity. Nitrogen supply improved wheat grain yield with no effect on thousand-grain weight. Grain soluble sugars and gluten fractions were increased, but starch concentration was reduced, under high N. Mineral composition and polyphenol concentrations were also improved by N application. High-yielding genotypes had higher grain carbohydrates concentrations, while higher concentrations in grain minerals, gluten fractions, and polyphenols were recorded in the low-yielding ones. Decreasing the amount of N to one-third ensured a better N use efficiency but reduced durum wheat agronomic and quality traits.

The increase in the atmospheric CO2 concentration is predicted to influence wheat production and grain quality and nutritional properties. In the present study, durum wheat (Triticum durum Desf. cv. Sula) was grown under two different CO2 (400 versus 700 μmol mol–1) concentrations to examine effects on the crop yield and grain quality at different phenological stages (from grain filling to maturity). Exposure to elevated CO2 significantly increased aboveground biomass and grain yield components. Growth at elevated CO2 diminished the elemental N content as well as protein and free amino acids, with a typical decrease in glutamine, which is the most represented amino acid in grain proteins. Such a general decrease in nitrogenous compounds was associated with altered kinetics of protein accumulation, N remobilization, and N partitioning. Our results highlight important modifications of grain metabolism that have implications for its nutritional quality.

While the general effect of CO2 enrichment on photosynthesis, stomatal conductance, nitrogen elemental content or yield has been documented, there is still some uncertainty as to whether there are interactive effects between CO2 enrichment and other factors (such as temperature, geographical location, water availability and cultivar). In addition, the metabolic coordination between leaves and grains, which is crucial for crop responsiveness to elevated CO2, has never been examined closely. Here, we addressed these two aspects by taking advantage of several FACE experiments across five different countries using multi-level analyses. There was little effect of elevated CO2 on yield (except in USA) likely due to photosynthetic capacity acclimation, as reflected by protein profiles. Also, there was a significant decrease in leaf amino acids (threonine) and macro-elements (such as K) at elevated CO2, while other elements such as magnesium (Mg) or sulfur (S) increased. Despite the insignificant effect of CO2-enrichment on yield, grains appeared to be significantly depleted (as expected) in N, but also in threonine, the S-containing amino acid methionine and Mg. Overall, our results suggest a strong detrimental effect of CO2 enrichment on nutrient availability and remobilization from leaves to grains.

Cereal yield and grain quality may be impaired by environmental factors associated with climate change. Major factors, including elevated CO2 concentration ([CO2]), elevated temperature, and drought stress, have been identified as affecting C3 crop production and quality. A meta-analysis of existing literature was performed to study the impact of these three environmental factors on the yield and nutritional traits of C3 cereals. Elevated [CO2] stimulates grain production (through larger grain numbers) and starch accumulation but negatively affects nutritional traits such as protein and mineral content. In contrast to [CO2], increased temperature and drought cause significant grain yield loss, with stronger effects observed from the latter. Elevated temperature decreases grain yield by decreasing the thousand grain weight (TGW). Nutritional quality is also negatively influenced by the changing climate, which will impact human health. Similar to drought, heat stress decreases starch content but increases grain protein and mineral concentrations. Despite the positive effect of elevated [CO2], increases to grain yield seem to be counterbalanced by heat and drought stress. Regarding grain nutritional value and within the three environmental factors, the increase in [CO2] is possibly the more detrimental to face because it will affect cereal quality independently of the region.

The current study focuses on yield and nutritional quality changes of wheat grain over the last 166 years. It is based on wheat grain quality analyses carried out on samples collected between 1850 and 2016. Samples were obtained from the Broadbalk Continuous Wheat Experiment (UK) and from herbaria from 16 different countries around the world. Our study showed that, together with an increase in carbohydrate content, an impoverishment of mineral composition and protein content occurred. The imbalance in carbohydrate/protein content was specially marked after the 1960’s, coinciding with strong increases in ambient [CO2] and temperature and the introduction of progressively shorter straw varieties. The implications of altered crop physiology are discussed.

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