Phosphorus and Carbon Cycling Directed by Spatial Plasticity in Root Exudation
EMSL Project ID
51648
Abstract
Plant root exudates provide a significant carbon (C) source for rhizosphere microbial communities. In return, these communities help mobilize nutrients needed for plant growth. For instance, biogeochemical cycling of phosphorus (P) in the rhizosphere is directed by a suite of bacterial, fungal, and root processes acting on geochemical sources of P which themselves are heterogeneously distributed in soil. While previous studies have identified increased root exudation as one strategy plants use to stimulate P mobilization in response to limitation, most of these studies were at relatively large, integrated scales and not spatially resolved. We hypothesize that plasticity in root physiology enables spatial localization of root exudation at the sub-mm to 10 mm scales in order to maximize P return to a plant by leveraging dispersed microbial and geochemical microenvironments within soils. We propose to evaluate this hypothesis using switchgrass microcosms in an effort to better understand the fundamental controls of nutrient delivery from soil to this bioenergy crop. Enhanced understanding of the linkages between C and P cycling in the rhizosphere will support switchgrass growth from marginal lands in support of DOE's mission focus in bioenergy production. We will use a series of spatially-specific measurements to track the linkage between plant C delivery to and the resulting P mobilization within the rhizosphere. We will implant P resource islands within our microcosms and use 13C labeling (using 13CO2) combined with a number of spatially resolved techniques to track plant uptake of CO2 and release of resulting organic C through root exudation. We will identify spatial foci of root exudation and track shifts in the chemical composition of these exudates when located near or distal to known P resources. We will use spatially focused protein extraction and analysis to evaluate dominant microbial taxa active within P amended or replete zones and identify (through a 13C tracer) taxa showing closest metabolic connectivity to the host plant in each of these zones. We will then map the total and bioavailable (aqueous) P pools in relation to observed root exudation and microbial activity.
Taken together, our planned analyses will leverage spatial assessment to better understand the extent of root plasticity (through exudation) prompted by heterogeneous distribution of nutrient resources and the implications of this plasticity on nutrient return. We will spatially evaluate the linkage between C delivery into the rhizosphere through root exudation, microbial consumption of this material, and the resulting nutrient (P) mobilization to support plant growth in an attempt to better understand adaptation to nutrient distribution. While P can be abundant in many soils, most of this P is not bioavailable and thus does not stimulate plant biomass production. Fertilizer application can be used to circumvent P limitations. However, economic constraints, concerns over environmental impact, and fundamental limits in P reserves suitable for mining can limit future P application to soils. A better understanding of interactions between plants, microbial communities, and the geochemical environments within the rhizosphere will be able to guide future efforts to improve P delivery from natural soils to bioenergy crops and thereby improve the viability of biomass production on marginal lands.
Project Details
Project type
Exploratory Research
Start Date
2020-12-01
End Date
2022-04-22
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members