Smarter Stomata: Emergent technologies unlocking yield potential in a changing climate

Stomata, the gatekeepers of leaf gas exchange, regulate carbon dioxide uptake and water loss, functions increasingly critical as crops face more frequent, intense heat and drought. Under dry conditions, stomatal conductance (gs) typically decreases, limiting carbon assimilation and yield. Heat stress, by contrast, elicits variable gₛ responses: sometimes increasing to facilitate transpirational cooling, while at other times decreasing, especially when combined with drought. Heat and drought also induce complex, context-dependent shifts in stomatal anatomy. Smaller, denser stomata improve drought resilience in some cases, while reduced density confers greater tolerance in others. The optimal stomatal ideotype remains unknown, and different or even opposing traits may confer resilience dependent on the environmental scenario. Substantial genotypic variation in gs and stomatal anatomy, high heritability and co-localised quantitative trait loci (QTL) for stomatal traits and yield highlight their untapped potential as breeding targets for climate-resilient crops. However, stomatal traits remain largely absent from breeding pipelines due to challenges of phenotyping at scale. This is changing rapidly. Advances in deep learning, porometry, digital microscopy, and remote sensing now enable high-throughput measurement of stomatal physiology and anatomy. Next-generation breeding technologies including Clustered-Regularly-Interspaced-Short-Palindromic-Repeats (CRISPR), multi-omics approaches, and artificial inteligence-driven ideotype selection models could revolutionise breeding, allowing precise engineering of stomatal traits for resilience to environmental stress. The time has come to move beyond characterising stomatal traits and start actively incorporating them into breeding strategies. By leveraging these technologies, stomatal traits can become high value targets, unlocking their potential to enhance crop performance in a hotter, drier future.