b'Yotam Zait, an assistant professor at the Hebrew University, Faculty of Agriculture, Rehovot, Israel, did the initial research in Assmanns lab. Penn State University professor of plant biology Sarah AssmannI had been intrigued since I was a graduate student in thepromoted stomatal opening. Follow-up experiments showed 1980s of evidence in the plant physiological literature thathow sugars influenced carbon dioxide uptake and water loss, such messengers existed, she says. Advances in metabolomicspainting the first complete picture of how these internal mes-convinced me that the necessary mass spec techniques weresengers drive stomatal behavior.now available to catalog the apoplastic metabolome, therebyFor seed companies, these results provide a clear, testable identifying candidate mesophyll messengers that could thenmechanism to influence a trait that has always been difficult be tested by other techniques to determine whether or not theyto breed for: the balance between carbon gain and water loss. played a messenger role. With climate variability putting pressure on water availability, What followed was a global collaboration and a team thatthe ability to identify or engineer lines with more precise sto-extracted apoplastic fluid, the liquid between plant cells, frommatal control could offer major agronomic advantages.Arabidopsis and fava bean leaves exposed to red light and dark-ness. They identified 448 unique metabolites, including sugarsWhat It Means for Real-World Cropsand maleic acid, which increased in light conditions. Importantly, the team demonstrated that the identified messen-That knowledge gives the seed industry a new set of physi- gers function not only in model plants but also in crop species ological and molecular markers that could be used to screenlike fava beans. That opens the door for broader agricultural germplasm or develop traits related to stomatal efficiency.applications.Understanding how internal metabolites guide stomatalIt is notable that we demonstrated that these messengers function can complement conventional breeding and biotechfunction not only in the model plant Arabidopsis but also in a approaches that seek to enhance photosynthesis, water retentioncrop species, fava beans, Assmann says. This suggests a com-and yield stability. monality of function across plant species. Understanding these messengersand potentially elucidating otherscould help Unlocking a New Trait Target for Seed Innovation in the creation of crops with improved water use efficiency.Plant biologists have an identified set of plant hormones,The discovery could also improve phenotyping technolo-Assmann says. An interesting question for future research isgies. With 448 metabolites now cataloged from apoplastic fluid, whether any of the non-hormone metabolites that we iden- researchers and breeders have a new set of potential biomark-tified in apoplastic fluid are actually playing a role as planters for screening stomatal behavior and stress resilience. These hormones, in addition to their recognized function, analogousbiological insights could be integrated into digital platforms to sugars being both signals and a source of energy. and predictive models for faster trait evaluationstreamlining What allowed this research to succeed where others hadthe seed development pipeline from lab to field.stalled was its scope. Were focused on understanding how plants sense and What really allowed us to make this advance was the col- respond to environmental conditions, Assmann says. Plants laborative effort of many different laboratories across the globe,cant uproot themselves and find somewhere else to live; they each with their own area of expertise, which included metabo- have to deal with whatever the environment throws at themlomics, biochemistry, electrophysiology, and plant physiology,increasingly drought and heat stressso we study what makes she says. plants resilient, from the very specific molecular level all the By carefully isolating the epidermis and exposing it toway up to whole plant physiology and field experiments, with sugars under red light, the researchers demonstrated that sugarsthe goal of improving crop productivity.28 SEEDWORLD.COM/CANADA JANUARY 2026'