European Journal of Sustainable Agroecosystems

Background: Extreme weather events becoming more common and severe is caused by human made climate change, which threatens food security. Zea mays (maize) is one of the important C4 crops because it suffers heavily from droughts combined with high temperatures. While at the same time C4 photosynthesis is much more efficient in terms of water consumption and heat tolerance than C3 systems, drought and heat stress combined (CDHS) cause both physiological and metabolic problems which go beyond the regular acclimatization ability of maize.
Objective: The objective of this review paper is to summarize recent literature on physiological and metabolic reprogramming of Zea mays under conditions of CDHS, evaluate the limits of C4 photosynthesis under joint abiotic stresses, and show this information as a practical input in breeding climate-tolerant cultivars.
Sources of Literature: A thorough investigation was executed across Scopus, Web of Science, and PubMed, focusing on journal articles which have undergone the process of peer review, agricultural reports from around the globe, and metabolic modeling studies recorded mainly between 2015 and 2026.
Biggest Discovery: While facing CDHS (combined effects of drought, heat, and salinity), maize undergoes a notable drop in its stomatal conductance, mesophyll conductance, and photosystem II (PSII) efficiency. The combined stress triggers a metabolic changeover, i.e. carbon will be channeled towards producing osmoprotectans (i.e. soluble sugars, raffinose family oligosaccharides) and defense-related amino acids (i.e. proline, branched-chain amino acids). Genome-scale metabolic models (GSMs) and multi-omics information make it clear that exposure to CDHS produces specific types of pathways that were never observed during isolated stress and has had a major negative effect on the CO2-concentrating mechanism (CCM) along with ROS molecules’ production.
Research Deficiencies: There exists a large knowledge gap in our understanding of the spatiotemporal dynamics of mesophyll conductance while under CDHS, as well as a lack of comprehension of the connection between changes in metabolic processes below-ground (roots) with those occurring aboveground (canopy). Moreover, work is still needed in applying controlled environment omics data to field conditions.
Conclusion: It is very important to understand the interactive effects of combined heat and drought on the C4 metabolism. Future research on crop improvement should focus on the use of modern advances in high-throughput phenotyping, genome editing (CRISPR/Cas), and systems biology.