Collaborative Research: Elucidating grass-specific responses to soil and atmospheric drought.

About This Grant

With ~40% coverage of the terrestrial biosphere, grasses represent one the major plant types on Earth; this percentage excludes additional coverage by all major grain crops, which are also grasses. Despite the global importance of grasses, significant gaps in understanding remain in how grasses respond to drought. The evolution and expansion of grassland biomes came at the expense of forests and was precipitated by an increase in aridity; therefore, grass evolution, physiology, and ecology are inextricably linked to the acquisition, use, and movement of water. The aim of this proposal is to provide a better understanding of grass physiological responses to drought from the cellular to ecosystem scales. The current understanding of plant responses to drought is dominated by data on woody plants, particularly trees, and this understanding does not translate readily to grasses. Elucidation of these drought response will enhance our understanding of wild grasses to drought, as well as discover relevant physiological responses for crop improvement. Additionally, the PIs will conduct the immersive data-collection and instrument training ecophysiology workshop for graduate students (Phys-Fest). This Phys-Fest will occur in the urban environment of Philadelphia. Urban environments can provide key ecosystem services, and when explicitly managed, these environments enhance overall human well-being. Participants are trained in four primary ecophysiological research areas and are provided with close interaction with faculty instructors, as well as evening activities designed to promote professional development and science communication. Several novel and previously unexplored aspects of grass physiology are developed within this proposal under the guiding question: How do grasses, individually and at the ecosystem scale, respond to changes in soil moisture and leaf-to-air vapor pressure deficit (VPDL)? This question is distilled into more specific questions that will be answered via the research plan: (i) What are the physiological and anatomical mechanisms by which grasses control stomatal sensitivity through changes in VPDL? (ii) How do grasses maintain leaf-level gas exchange at leaf-water potentials that are near or more negative than the turgor-loss point? (ii) How do physiological responses coupled with plant-atmosphere interactions affect grassland responses to soil and atmospheric drought? The proposed research will be comprised of lab, greenhouse, and field work at two N. American prairie sites. The field sites were chosen because of their ecological and phylogenetic relevance: the tall-grass prairie site is dominated by C4 Andropogoneae and the short-grass prairie site is dominated by C4 Chloridoideae and C3 Pooideae. These grasslands exist on opposite ends of the precipitation spectrum across the Great Plains and these grass lineages are globally dominant. This proposal was supported by the Integrative Ecological Physiology Program in the Division of Integrative Organismal System and the Ecosystem Science Cluster in the Division of Environmental Biology. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.