Complementary analysis of freeze-dried and frozen-hydrated plant tissue by electron-probe X-ray microanalysis: Spectral resolution and analysis of calcium

Abstract

Automated methods of peak determination including peak location, background determination and peak deconvolution are presented. Special attention is given to the problem of severely overlapped peaks, such as the primary calcium peak (Caka) and the secondary potassium peak (Kkβ). A method, based on the principle of electronic transitional probabilities, is presented for estimating Ca in the presence of a high background of K, and limitations of resolution are discussed. Minimally detectable concentrations of elements in prepared frozen-hydrated standards are estimated empirically by analysis of the relative variance. Minimally detectable Ca is estimated in both frozen-hydrated and freeze-dried tissue standards. Using our instrumentation and procedures P, S, Cl and K are detectable down to 24 mM, while Na and Mg are only detectable down to 38 mM in frozen-hydrated tissue. In the presence of 100 mM K, detection of calcium is possible down to 22 and 2 mM in frozen-hydrated and freeze-dried tissue, respectively. As an example, total Ca is shown not to conform to the radial gradient of K across the lettuce (Lactuca sativa L.) taproot.

Subcellular localisation of Cd and Zn in the leaves of a Cd-hyperaccumulating ecotype of Thlaspi caerulescens

“…This difference may be attributed to the different ecotypes used, different determination methods, or growth conditions. Compared to our quantitative method, EDXMA is a semi-quantitative and relatively insensitive method (Lazof and La¨uchli 1991), providing only the relative concentration of Zn (Ku¨pper et al 1999).…”

Selenium in Plants: Uptake, Functions, and Environmental Toxicity

“…This idea, however, has not yet been tested experimentally. A possible approach may be to localize Se intracellularly by electron probe X-ray microanalysis using preparation techniques similar to the ones described by Lazof and Lauchli (1991) and Lauchli and Boursier (1989).…”

Cryo-scanning electron microscopy (CSEM) in the advancement of functional plant biology: energy dispersive X-ray microanalysis (CEDX) applications

“…The Na Ka peak coincides with the O Kb peak, and it is necessary to correct the Na reading by subtraction of a proportion of the O Ka peak, which may be measured in Na-free standard solution. A similar correction to Ca Ka peak needs to be applied for the overlap with the K Kb peak (Lazof and Läuchli 1991a).…”