PARENT SESSION
Contributed Oral Session 166: Soil Communities and Plant-Root Interactions
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 522 A, Level 5, Palais des congrès de Montréal
Patterns of water potential gradients around roots in soil as reported by microbiosensors.
Herron, Patrick*,1, Gage, Dan1, Cardon, Zoe1, 1 University of Connecticut, Storrs, CT
ABSTRACT- Fine scale patterns of water availability around roots influence the activity of microbes, the availability of nitrogen and phosphorous to the plant, and likely the availability of carbon to the microbes. These significant gradients of water availability, operating across fractions of millimeters, can only be quantified with tools of comparable spatial resolution. We are using the microbiosensors Pseudomonas putida KT2442 and Pantoea agglomerans BRT98, both containing a plasmid-borne fusion of the osmotically controlled proU promoter and the reporter gene gfp, to quantify gradients of total soil water potential around the roots of corn. These biosensors produce green fluorescent protein (GFP) as a function of osmotic potential in their microenvironment; GFP can be detected in nonsterile soils nondestructively using fluorescence microscopy. Results from reporter bacteria around secondary roots indicate rhizosphere soil is more moist around the root tip, and less moist around the root's active uptake zone, consistent with hydraulic isolation of the tip from effects of the transpiration stream. We plan to substitute the reporter gene lux for gfp in our water-sensing bacteria to provide water gradient measurements on a slightly larger scale across whole root systems. These microbiosensors provide the first empirical assessment of extremely small-scale gradients in water potential in situ, gradients that previously could only be estimated by mathematical modeling.
Key words: water potential, root, microbiosensor, gfp