Introduction
Photosynthesis and Carbon–Nitrogen Balance
Micronutrient Decline
Stress Metabolites and Secondary Compounds
Crop Adaptation Strategies
Conclusions
References
As climate pressures intensify, crops are growing faster but losing vital nutrients. Understanding these biochemical shifts is essential for building resilient, nutrient-dense food systems in a changing climate.
Image credit: DC Studio/Shutterstock.com
Introduction
Rising atmospheric carbon dioxide (CO2), intensifying drought, and heatwaves are reshaping crops, resulting in yields that fall, pollination that falters, and the same plants carrying fewer minerals per gram as carbohydrate dilution and impaired root uptake lower zinc, iron, and other essential nutrients. These stressors, compounded by ozone and extreme weather, also threaten fruits, vegetables, legumes, fisheries, and nuts, shifting where food can be grown and what quality reaches plates.
Life scientists care because nutrient density is biology’s first mile: it defines enzyme cofactors, hemoglobin synthesis, immune tone, and neurodevelopment, and thus population risks for anemia, infections, child development, and global public health.1
This article explains how elevated CO₂, heat, drought, and ozone reprogram plant biochemistry, shifting the carbon-nitrogen balance, impairing mineral uptake, altering secondary metabolites, and lowering nutrient density with public health consequences. Overall, recent reviews show that these nutritional declines are now a recognized component of “hidden hunger,” as elevated CO₂ simultaneously enhances yield yet lowers nutritional quality across major staples.1,2
Photosynthesis and Carbon–Nitrogen Balance
Elevated CO2 raises the partial pressure of CO₂ around the ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), which enhances carboxylation, reduces photorespiration, and increases the production of triose-phosphate that are later converted to sucrose and starch. Over time, the stimulatory effect may diminish, depending on the availability of nitrogen and water. This stronger carbon influx disrupts the carbon-nitrogen balance, as carbohydrates accumulate while nitrogen-rich compounds become diluted, especially when soil nitrogen is limited, resulting in lower protein and mineral concentrations in edible tissues.2
At the biochemical level, elevated CO₂ alters the regulation of photosynthesis and photorespiration through changes in RuBisCO kinetics, while also suppressing genes involved in nitrogen assimilation. This limits flux through the glutamine synthetase/glutamate synthase (GS/GOGAT) cycle, which converts inorganic nitrogen into amino acids.
Free-air CO₂ enrichment (FACE) and controlled chamber studies confirm that while wheat and rice initially benefit from elevated CO₂ through enhanced photosynthetic rates, prolonged exposure reduces nitrogen, potassium, and phosphorus content in aboveground organs, an effect attributed to the “dilution” and limited N-assimilation mechanisms.2,3 In legumes, coordinated nitrogen fixation can partially offset these constraints, but responses remain context-dependent. In effect, CO₂ fertilization increases carbohydrate synthesis yet reduces nitrogen density, driving declines in protein and key minerals.2
Plants Are Struggling to Keep Up with Rising Carbon Dioxide Concentrations
Plants Are Struggling to Keep Up with Rising Carbon Dioxide Concentrations. Video credit: NASAGoddard/Youtube.com
Micronutrient Decline
In C3 crops, such as wheat, rice, and soybeans, elevated atmospheric CO₂ increases carbohydrate accumulation but leads to mineral dilution, resulting in plant tissues showing a ~8% lower overall mineral content, with notable reductions in nitrogen, iron, zinc, and other cations. Meta-analyses and FACE studies indicate that under CO2 concentrations expected by 2050, grain iron and zinc levels decrease by approximately 5 to 10%, while wheat protein concentrations drop by as much as 6 to 13% under elevated (eCO₂) conditions.1,2
This pattern is repeatedly observed in FACE and related field systems. Empirically, rice and wheat FACE/temperature free-air CO₂ enrichment (T-FACE) studies report declines in grain iron and zinc at higher CO₂. In contrast, combined CO₂ and temperature treatments can partially offset some mineral reductions but increase risks of toxic metal accumulation, such as cadmium and lead, in grains.1,3
Physiologically, three main mechanisms explain these outcomes.
- Elevated CO₂ reduces canopy transpiration, weakening the mass flow of minerals into roots and up the xylem, thereby lowering whole-plant mineral uptake.
- The CO₂-driven increase in carbohydrate synthesis outpaces nitrogen acquisition (“dilution effect”), which decreases grain protein and associated micronutrients such as zinc and iron.
- Elevated CO₂ disrupts nitrate assimilation and other nitrogen-related metabolic processes that rely on iron-sulfur enzyme cofactors, limiting phloem loading and the redistribution of amino-N and associated micronutrients to developing grains. Recent wheat FACE data confirm reductions not only in Fe and Zn but also in vitamins and polyphenols, linking biochemical shifts to declining antioxidant capacity in grains.1,2,3
Under heat and drought, plants redirect carbon and energy from growth to defense, upregulating secondary metabolite pathways that yield phenolics, flavonoids, and alkaloids. These compounds neutralize reactive oxygen species, stabilize cell membranes, and deter herbivores and pathogens. Climate-linked stressors such as higher temperature, altered rainfall, ultraviolet radiation, and elevated CO₂ can therefore raise concentrations of selected antioxidants (for example, phenolic acids and flavonols) or specific alkaloids via stress-activated transcription factors (examples: Tryptophan–Arginine-Lysine-Tyrosine motif transcription factors (WRKY), Myeloblastosis transcription factors (MYB)).
Yet responses are species- and context-dependent: some plants show overall antioxidant gains, while others lose total phenolics or flavonoids despite increasing a few potent constituents (such as higher aloin in aloe under salinity). Experimental work has confirmed that transcription factors like WRKY, MYB, bZIP, and bHLH regulate these stress-induced shifts, affecting bioactivity and chemical stability in medicinal and food plants.4
For human nutrition, these shifts offer potential benefits: more phenolics and flavonoids can enhance dietary antioxidant capacity, anti-inflammatory effects, and cardiometabolic protection; some alkaloids confer neuroactive or antimicrobial actions at dietary levels. Stress can lower yields, dilute essential nutrients, or skew phytochemical profiles toward compounds that are bitter, less bioavailable, or bioactive at doses that approach toxicity.
Variability across seasons and regions complicates standardization for foods and herbal preparations, and changing profiles may alter drug-nutrient interactions. Net effects will depend on species, farming practices, and post-harvest handling, highlighting the need for targeted cultivation and quality monitoring.4
Crop Adaptation Strategies
Crop adaptation combines improved plant genetics (germplasm) with optimized environments. Biofortification prioritizes genotypes that sustain nutrient uptake by shaping the rhizosphere, recruiting nitrogen-fixing and phosphorus-solubilizing microbes, while breeding climate-resilient varieties complements this strategy. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated protein 9 (Cas9), referred to as CRISPR-Cas9, enables precise editing of rhizosphere-signaling and susceptibility loci.
In rice, editing Oryza sativa Chitin Elicitor Receptor Kinase 1 (OsCERK1) and promoters of Oryza sativa Sugars Will Eventually be Exported Transporters (OsSWEET) confer resistance to Xanthomonas oryzae without yield loss, helping stabilize nutrient uptake under stress.
Complementary research highlights how specific root exudates (citric acid, flavonoids) recruit beneficial microbes such as Bacillus and Pseudomonas, strengthening nutrient cycling and disease suppression under variable moisture regimes.5
Controlled Environment Agriculture (CEA) principles translate to field water control, where Alternate Wetting and Drying (AWD) decreases methanogens, increases nitrifiers, and improves nitrogen cycling. Drip systems also enrich Plant Growth-Promoting Rhizobacteria (PGPR), such as Bacillus and Pseudomonas, thereby supporting plant health. AWD can reduce irrigation water by 23 to 32% while increasing yield by ~6%, enhancing irrigation efficiency and profitability under climate pressure. Together, biofortified, stress-tuned genotypes, gene editing with CRISPR-Cas9, and CEA-inspired irrigation form a climate-resilient toolkit to preserve nutrient density and yield as conditions intensify.5
Download your PDF copy now!
Conclusions
Long-term, climate-driven nutrient dilution will reshape food security by lowering the protein, iron, zinc, and B vitamins in staples, while heat and drought pressure yield. Populations on marginal diets face rising risks of anemia, stunting, impaired cognition, and metabolic disease as carbohydrate density outpaces micronutrients. Global health policy should integrate climate mitigation with nutrient resilience, encompassing crop biofortification, diversified food systems, soil and water stewardship, and fortification where necessary.
Integrating rhizosphere microbiome management and crop diversification can buffer nutrient losses while reducing greenhouse gas emissions from farming systems. Surveillance must monitor nutrient density, not just tonnage, and link agriculture with nutrition programs. Trade, safety nets, and funding should prioritize resilient, nutrient-dense crops to protect metabolic health across generations.
References
- Semba, R. D., Askari, S., Gibson, S., Bloem, M. W., & Kraemer, K. (2022). The potential impact of climate change on the micronutrient-rich food supply. Advances in Nutrition. 13(1): 80-100. DOI:10.1093/advances/nmab104, https://academic.oup.com/advances/article/13/1/80/6441392
- Ekele, J. U., Webster, R., Perez de Heredia, F., Lane, K. E., Fadel, A., & Symonds, R. C. (2025). Current impacts of elevated CO2 on crop nutritional quality: a review using wheat as a case study. Stress Biology. 5(1). DOI:10.1007/s44154-025-00217-w, https://link.springer.com/article/10.1007/s44154-025-00217-w
- Santos, C. S., Habyarimana, E., & Vasconcelos, M. W. (2023). The impact of climate change on nutrient composition of staple foods and the role of diversification in increasing food system resilience. Frontiers in Plant Science. 14. DOI:10.3389/fpls.2023.1087712, https://www.frontiersin.org/articles/10.3389/fpls.2023.1087712/full
- Alum, E. U. (2024). Climate change and its impact on the bioactive compound profile of medicinal plants: implications for global health. Plant Signaling & Behavior. 19(1). DOI:10.1080/15592324.2024.2419683, https://www.tandfonline.com/doi/full/10.1080/15592324.2024.2419683
- Aminurrasyid, A. H. B., Mohd Ikmal, A., & Nadarajah, K. K. (2025). The Rice-Microbe Nexus: Unlocking Productivity Through Soil Science. Rice. 18(1). DOI:10.1186/s12284-025-00809-0, https://thericejournal.springeropen.com/articles/10.1186/s12284-025-00809-0
Further Reading
Last Updated: Nov 14, 2025