THE INTERACTIONS THAT PLANTS HAVE WITH MICROBES HAVE CRITICAL IMPLICATIONS FOR PLANT GROWTH AND HEALTH. WE SEEK TO UNDERSTANDHOW PLANTS CAN ACTIVELY REGULATE THE MICROBIAL COMMUNITIES THEY ASSOCIATE WITH. IT IS WELL-ESTABLISHED THAT ROOTS ALTER THE PH OFTHE SURROUNDING SOIL AND THAT SOIL PH HAS A STRONG EFFECT ON MICROBIAL COMMUNITIES, HOWEVER LEAVES MAY ALSO ALTER THE PH LEVELSOF THEIR SURFACES, THOUGH THIS IS NOT A TOPIC THAT HAS BEEN WELL-EXPLORED. THERE ARE THREE MAJOR GOALS OF THIS PROJECT: (1) DETERMINEHOW DIFFERENT PLANT SPECIES ALTER THE PH LEVELS OF WATER ON THEIR SURFACES, (2) DETERMINE THE GENES AND GENE PATHWAYS INVOLVEDIN THE PROCESS OF PH MODIFICATION IN THESE DIFFERENT SPECIES, AND (3) EXAMINE HOW MICROBIAL COMMUNITIES CHANGE IN RESPONSE TOTHE CHANGE IN PH LEVELS ON THE LEAVES. ADDITIONALLY WE WILL WORK ON BUILDING A PUBLIC DATABASE CONTAINING INFORMATION ON THENATURAL VARIATION OF LEAF PH LEVELS OF A WIDE VARIETY OF SPECIES, WITH HOPES OF EXPANDING THE DATABASE TO INCLUDE AS MUCH PLANTDIVERSITY AS POSSIBLE.