Determination of Ammonium Turnover and Flow Patterns Close to Roots Using Imaging Optodes

Abstract

The physical effect of nitrogen upon plants has been studied thoroughly; however, direct studies of nitrogen turnover close to roots have been limited by analytical techniques with low spatial and temporal resolution. Thus, little is known about differences in turnover taking place along and between intact root structures over time as well as how root arrangement, root cell type, plant age, microbial activity, and the dark/light cycle influence uptake and supply of nutrients to root structures. In this study an imaging (planar) optode was used to quantify ammonium over time close to an intact root system of a large fruit bearing tomato plant (Lycopersicon esculentum). Images throughout the experiment made it possible to define the ammonium depletion zone and active turnover potential as well as determine turnover rate and flow patterns around the root system over time. The results indicated that ammonium uptake for tomato plants proceeds over the entire root structure but transverse thin peripheral roots are about twice as efficient as the main root and that the uptake process might influence nutrient availability. The flow patterns close to the root structure revealed that apical regions seem to have a central role in ammonium acquisition.

Two decades of chemical imaging of solutes in sediments and soils – a review

“…Optode images are often processed using ImageJ, Matlab or similar software packages [77,82,83] which allow for the simultaneous processing of image series. The information contained in image time series can be extracted as average area concentrations [225,226], as the size of an area with a specific solute concentration [225,226], solute flow patterns [83,227] or single pixel concentration profiles [82,99,228]. Although single pixel profiles contain only a fraction of the information compared to the original image, profiles are useful to highlight small-scale variability and simplify the calculation of solute release or consumption rates.…”

“…This GFP technique allowed for root identification in situations where roots of two species grew closely together, showing that rhizosphere pH effects were the assimilation by the roots. Reproduced with permission from Strömberg [227]. Copyright 2008 American Chemical Society.…”

Signal Enhancements in Plasmon Assisted Fluorescence Ratiometric Imaging Optodes

“…Also the analytical performance such as sensitivity, limit of detection (LOD), and expected operational lifetime were calculated for each pixel and presented as statistical images [9]. After improvements of the infinity corrected imaging system as well as a high throughput macro imaging techniques were developed [10], the technique was ready for research applications such as studying ammonium uptake close to roots [11], and multiple fertilizer release studies (using a high throughput imaging system) in different soils [12] over long time periods up to 11 days.…”

Strategies and methods for studying the rhizosphere—the plant science toolbox

“…Continuous fluorescence measurements of the undisturbed system are taken from outside using a mobile polymer optical fibre system to apply the light for fluorescence excitation and to monitor fluorescence emission from the detector foil. Similar techniques are available for measuring O 2 concentrations and imaging optodes with potential perspectives for rhizosphere applications have been developed also for the detection of minerals such as NH 4 + , various heavy metals or enzyme activities (Stromberg 2006(Stromberg , 2008.…”

“…A number of studies have investigated genotypic variation in mechanisms which take place, completely or partially, in the rhizosphere of cereals, particularly maize, wheat and rice (Fageria et al 1988;Fageria and Baligar 1997a, b;Ciarelli et al 1998;Manske et al 2000;Wissuwa and Ae 2001a, b;Osborne and Rengel 2002;Wang et al 2005;Zhu et al 2005;Liao et al 2004;2008). Most of these studies have been targeted to nutrient efficiencies, most notably that of N, P and K with most progress being made for P (Rengel and Marschner 2005).…”