Plants can overcome environmental stress by dispersing to less stressful habitats, adapting to the stress, or associating with other organisms, such as microbes, that help reduce the stress. Although the third strategy of coping with stress has received very little attention, there is increasing evidence that it is both common and effective. Soil bacteria called rhizobia act like natural fertilizer by converting nitrogen in the atmosphere into a form that at least some plants can use. In return, those plants provide energy to the rhizobia. The goal of this study is to determine whether rhizobia help plants survive under extreme water stress. This research is important because increasing drought stress is predicted for much of the world under global climate change and rhizobia are one of the most likely ways that plants may overcome that stress. This has practical implications. For example, understanding the plant-rhizobium partnership may help reduce application of synthetic fertilizers or unnecessary use of water in agriculture systems. Results will be shared broadly through presentations at national and regional meetings as well as in high school classrooms and in newsletters for naturalists and land managers. The researchers will also create and publish inquiry-based activities for high school students that are aligned with the Advanced Placement (AP) biology Curriculum.
Specifically, this research will investigate how resource mutualists influence plant adaptation to soil moisture in the field. Using the legume-rhizobia mutualism as a model system, investigators aim to expand understanding of the mechanisms contributing to local adaptation, how species interactions influence local adaptation, and the traits underlying adaptation. Three specific questions will be addressed: (1) Are plants locally adapted to soil moisture conditions? (2) Do resource mutualists contribute to plant adaptation to soil moisture? And, (3) what plant traits drive adaptation to wet vs. dry environments? These questions will be tackled with an integrated set of reciprocal transplant experiments across multiple sites differing in soil moisture, with manipulative greenhouse experiments, and with molecular analyses.
