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 graduateWhat allowed this research to succeed where student in the 1980s of evidence in the plant physi- others had stalled was its scope.ological literature that such messengers existed,What really allowed us to make this advance was she says. Advances in metabolomics convincedthe collaborative effort of many different laboratories me that the necessary mass spec techniques wereacross the globe, each with their own area of exper-now available to catalog the apoplastic metabo- tise, which included metabolomics, biochemistry, lome, thereby identifying candidate mesophyllelectrophysiology, and plant physiology, she says.messengers that could then be tested by otherBy carefully isolating the epidermis and expos- Plants cant techniques to determine whether or not theying it to sugars under red light, the researchersuproot played a messenger role. demonstrated that sugars promoted stomatal What followed was a global collaboration andopening. Follow-up experiments showed howthemselves and a team that extracted apoplastic fluid, the liquidsugars influenced carbon dioxide uptake and waterfind somewhere between plant cells, from Arabidopsis and favaloss, painting the first complete picture of how bean leaves exposed to red light and darkness.these internal messengers drive stomatal behavior. else to live; they They identified 448 unique metabolites, includingFor seed companies, these results provide ahave to deal sugars and maleic acid, which increased in lightclear, testable mechanism to influence a trait that conditions. has always been difficult to breed for: the balancewith whatever That knowledge gives the seed industry a newbetween carbon gain and water loss. With climate set of physiological and molecular markers thatvariability putting pressure on water availability, thethe environment could be used to screen germplasm or developability to identify or engineer lines with more pre- throws at them.traits related to stomatal efficiency. Understandingcise stomatal control could offer major agronomic how internal metabolites guide stomatal functionadvantages.Sarah Assmann can complement conventional breeding and bio-tech approaches that seek to enhance photosyn- What It Means for Real-World Cropsthesis, water retention and yield stability. Importantly, the team demonstrated that the identi-fied messengers function not only in model plants Unlocking a New Trait Target for Seedbut also in crop species like fava beans. That opens Innovation the door for broader agricultural applications.Plant biologists have an identified set of plantIt is notable that we demonstrated that these hormones, Assmann says. An interesting ques- messengers function not only in the model plant tion for future research is whether any of theArabidopsis but also in a crop species, fava beans, non-hormone metabolites that we identified inAssmann says. This suggests a commonality of apoplastic fluid are actually playing a role as plantfunction across plant species. Understanding these hormones, in addition to their recognized func- messengersand potentially elucidating otherstion, analogous to sugars being both signals and acould help in the creation of crops with improved source of energy. water use efficiency.32/ SEEDWORLD.COMDECEMBER 2025'