Plants that are exposed to gradually increasing water stress over a long period of time become "drought hardened." In this state, they can survive drier conditions than plants that are shocked suddenly by drought after having an abundance of water. In this project, we are testing the two-part hypothesis that: (1) chloroplasts must maintain an optimum size in order to exhibit efficient photosynthesis, and (2) that drought hardening is a process whereby plants synthesize substances that prevent their chloroplasts from shrinking as they dry. If it is true, the hypothesis would explain at least one aspect of drought hardening.//