In-situ application of stable isotope tracers in the rhizosphere of an oak seedling

Abstract

In a controlled rhizotrone experiment, stable isotope tracers of Mg, Ca and K were applied directly to the rhizosphere of an oak seedling using a 2D-array of micro ceramic cups. Before starting isotope application the oak root induced a significant reduction of K + , Ca 2+ , Mg 2+ and NO 3 À in the soil solution of the rhizosphere, as well as an increase of Al 3+ . The effect of adding stable isotopes in the soil (soil solution and exchangeable cations) was mainly restricted to a distance of about 1 cm from the point of application. All stable isotopes were taken up by the oak seedling, especially Ca which according to leaf analysis was in the range of insufficiency. As expected, Ca showed low mobility in the phloem, resulting in a low percentage of label in the root tip as compared to other root segments. Our experiment proved, that in-situ application is an easy to handle tool for carrying out tracer studies in real soil.

Sampling, defining, characterising and modeling the rhizosphere—the soil science tool box

“…Gradients around roots can be determined using microcosms of the root mat type and analyzing slices of soil at various distances from the root mat (Kuzyakov et al 2003). Microcosms of the "Hohenheim" type allowed to assess the equilibration of stable isotope labels for Mg, K and Ca between rhizosphere soil and solution (Göttlein et al 2005). Autoradiography on flat microcosms provides non-invasive 2D imaging of the distribution of radioactive isotopes.…”

A depth‐controlled tracer technique measures vertical, horizontal and temporal patterns of water use by trees and grasses in a subtropical savanna

“…Techniques that introduce tracers into the soil are more promising because they can constrain descriptions of water use to specific locations (i.e. vertical, horizontal, and temporal; Gottlein et al. , 2005).…”

“…Techniques that introduce tracers into the soil are more promising because they can constrain descriptions of water use to specific locations (i.e. vertical, horizontal, and temporal;Gottlein et al, 2005). While elements such as lithium (Li), strontium (Sr), and cesium (Cs) have been used as tracers (Mamolos et al, 1995;Bonanomi et al, 2005;Rodriguez et al, 2007), studies using deuterated water (D 2 O) show the most promise because plant roots typically do not distinguish D 2 O from H 2 O and, unlike some tracer elements, D 2 O is unlikely to accumulate variably in different plant parts (Dawson & Ehleringer, 1993;Takahashi, 1998;Webb & Longstaffe, 2003; but see Ellsworth & Williams, 2007).…”

Seasonal Fe Uptake of Young Citrus Trees and Its Contribution to the Development of New Organs

“…This uptake pattern is a consequence of the finite capacity of trees to use available soil elements and the capacity to self-regulate net uptake once achieving capacity [32]. By contrast, in some works carried out with 26 Mg and 44 Ca [33,34], the authors found lower Mg tracer recovery in roots compared to Ca, due to dilution of root 26 Mg and internal cycling of Mg through the phloem sap flow [35]. Mg may undergo a rapid transfer to the aboveground biomass compartment without homogenously labeling the root biomass compartment in comparison to Ca.…”