Visualizing the three-dimensional organization of biopolymers within the plant root-matrix to understand the physiology and

Lead Institution: 
Clemson University
Closed Date: 
Friday, September 30, 2016
Principal Investigator: 
Nishanth Tharayil Santhakumar
Project ID: 
48371
Abstract: 

Plant roots contribute to a majority of carbon stored in soils. However, we still lack the parameters that can accurately forecast root decomposability, which hinders our ability to predict future carbon budget of terrestrial ecosystems. Ratios of elements (carbon, nitrogen) and quantity of compounds (lignin) used to predict the decomposability of aboveground plant tissues have failed to predict root decomposability. The variation in the decomposability of roots and leaves arises from the fundamental difference in their structural makeup and the environments they occupy. While leaves have a planar geometry that has more surface area per unit mass, roots, being cylindrical, has a lower surface of exchange with its immediate surroundings. Apart from performing the functions of anchorage and resource uptake, roots also constantly strive to protect itself from toxins, pests and pathogens that are ubiquitous in soils. This could lead to the differential production and strategic distribution of polymers that allow the roots to defend themselves in the soil environment without compromising their functions. We hypothesize that the organization of biopolymers within different orders of roots would vary based on their local environments, and this differential distribution of biopolymers within the cylindrical root construct regulates the function and decomposability of roots. Our proposed work aims to develop a deeper understanding of the chemical composition and spatial distribution of heteropolymers such as cellulose, lignins, suberins and tannins within the three dimensional matrix of plant roots using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), confocal laser scanning microscopy (CLSM) and fluorescence lifetime imaging microscopy (FLIM). Using ToF-SIMS we propose to obtain the three dimensional distribution of biopolymers within the plant roots with unmatched chemical specificity. We will utilize confocal multiphoton/FLIM integrated microscopy to precisely identify the organization of lignin matrix and its localization at organelle level. We would further relate the above measurements to the traditional quantitative parameters (C:N, lignin) and to root decomposition (mass loss), to highlight the role of the differential distribution of biopolymers in regulating the functioning and decomposition susceptibility of roots. Characterizing the molecular level composition and spatial mapping of biopolymers in roots using ToF-SIMS and microscopic techniques would significantly advance our ability to predict decomposability of roots in terrestrial ecosystems, and would revolutionize our understanding on the structural construct of plant organs. EMSL provide a unique combination of relevant expertise and instrumentation to undertake the proposed study. Also, based on the results from ToF-SIMS and CLSM, the research team would be further able to pursue other related techniques in fully elucidating the molecular level spatial distribution of polymers in plant tissues. Such an integrated problem solving atmosphere is critical for successfully executing the intricate objectives proposed in this research.