Visualizing the chemical plasticity of plant roots in response to soil biotic and abiotic properties and developing a better framework to predict fine root decomposition
EMSL Project ID
50814
Abstract
Fine roots of Plants represent a major contributor to soil organic carbon storage. Despite its fundamental role in global carbon cycling, we know little about the factors controlling the residence time of carbon in fine roots. Although leaf litter decomposition is a function of litter chemistry, where higher nitrogen and lower lignin concentrations lead to faster decomposition, these chemical parameters have failed to predict fine root decomposition. This disparity could arise from the differences in the functions between roots and leaves, and the biotic and abiotic environments that they occupy. Fine roots reside in soil environments that are highly heterogeneous in biotic and abiotic properties. Soil heterogeneities could alter root bulk chemistry as roots rely heavily on the abundance, molecular composition, and spatial distribution of heteropolymers such as lignin and suberin to adapt to various environmental pressures and to maximize the resource uptake. Here we hypothesize that the disconnect of root decomposition from the factors controlling leaf decomposition could be due to the molecular-level chemical plasticity of roots in response to soil heterogeneities, which arises from the fundamental differences in the spatial distribution of protective heteropolymers within root matrix, the quantity of heteropolymers, and the composition of monomers in heteropolymers. Specifically, we predict that the fine roots which form in soil patches with different nutrient availabilities will vary in the abundance, composition and spatial distribution of protective heteropolymers. Since the resistance of heteropolymers to degradation depend on the identity of their monomers and the inter-unit linkages, this plasticity of root biopolymers would then impose a strong impact on root decomposition. We also predict that biotic interactions such as mycorrhizal colonization will interact with nutrient availability to affect root chemical construction and decomposition. To test these hypotheses, we will characterize the changes in the abundance, composition, and organization of root biopolymers under a series of experimentally manipulated nutrient micro-environments for tree species associating with different types of mycorrhizal fungi. We will further investigate how these chemical changes due to soil heterogeneities affect root decomposition in a decomposition study, in an attempt to develop a better framework for predicting root decomposition. We propose to characterize root biopolymers by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and confocal multiphoton/fluorescence lifetime imaging microscopy (FLIM) integrated microscopy. Using ToF-SIMS we will obtain the spatial distributions of biopolymers within the plant roots with unmatched chemical specificity. We will use confocal multiphoton/FLIM integrated microscopy to precisely identify the organization of lignin matrix and its localization at organelle level. Characterizing molecular-level biopolymer plasticity in fine roots by ToF-SIMS and microscopic techniques would revolutionize our understanding of how molecular-level chemical construction of fine roots affect ecosystem-scale nutrient budget and carbon cycling. Moreover, our previously funded EMSL project enabled us to elucidate the organization of heteropolymers in different orders of fine roots by ToF-SIMS and FLIM and optimize these methods for root tissues. This previous knowledge on ToF-SIMS and FLIM applications on root tissues is critical for us to successfully characterize molecular-level biopolymer plasticity subjected to soil nutrient heterogeneities and mycorrhizal association in the proposed project.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2019-10-01
End Date
2022-11-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Suseela V-, Tharayil N, Orr G, Hu D. 2020. Chemical plasticity in the fine root construct of Quercus spp. varies with root order and drought. New Phytologist (In press)