The Uptake and Distribution of Potassium in Roots of Duckweed (Lemna Minor L) As Measured using Low Temperature X-Ray Microanalysis
Lemna minor L. plants were grown in a 14 H light and 10 H dark regime at 298 K in a medium containing 2 mM [K+]. Roots, 20 mm long and photosynthetically active, were removed and prepared for low temperature microscopy using methods described elsewhere. Fracture faces were made using the AMRAY Biochamber and the analysis carried out using an AMRAY 1000A SEM fitted with an LaB6 gun and a Kevex Si (Li) x-ray detector at 15-17 kV and a beam current of 1-2 nA. A reduced raster (1.0 μm2) was placed at the centre of the cell being analysed, care being taken to avoid any contact with the cell walls. Samples were maintained at 100-110 K throughout analysis and an LN2 cooled anti-contamination device was inserted close to the specimen. The spectra were analysed using the peak/background (P/B) ratio technique following use of background subtraction and peak de-convolution routines. Between eight and twelve fracture faces were analysed for each of the ten sites along the length of the root and the data pooled and presented in Table I.