Effects of several inorganic ions on short-term glyphosate absorption by cultured plant cells were determined by measuring the glyphosate content of cells exposed to inorganic salts in a 0.01-mM glyphosate solution buffered at pH 5.7. Within 10 min, glyphosate absorption by potato and velvetleaf cells was stimulated about equally by 1.5 mM CaCl2 or 1.5 mM MgCl2 but was not affected by 1.5 mM KCl. Glyphosate absorption by both species increased linearly with log10 CaCl2 concentration; for velvetleaf cells, the response was greatest for CaCl2 concentrations greater than 0.2 mM. Over time of absorption, glyphosate concentration within velvetleaf cells approached an asymptote. Addition of 0.1 mM KH2PO4 inhibited glyphosate absorption by potato cells in the presence or absence of Ca2+ and Mg2+ salts; all other K+ salts tested had no effect. Glyphosate absorption by potato, velvetleaf, soybean, corn, and rice cells was stimulated by 5.0 mM CaCl2 but was inhibited by 0.1 mM KH2PO4 in the presence of 0.05 or 5.0 mM CaCl2.

A novel cryogenic electrostatic storage device consisting of two ion-beam storage rings with a common straight section for studies of interactions between oppositely charged ions at low and well-defined relative velocities is under construction at Stockholm University. Here we consider the prospect of using this new tool to measure cross-sections and rate coefficients for mutual neutralization reactions of importance in interstellar ion chemistry in general and specifically in cosmic pre-biotic ion chemistry.

The elemental composition of cells of Anabaena flos-aquae was investigated by energy-dispersive electron probe X-ray microanalysis (10 kV) of mixed phytoplankton samples obtained from different depths within a stratified eutrophic freshwater lake. Preliminary studies had indicated that at 10 kV, X-ray information was derived mainly from the peripheral region (up to 1–2 μm) of cells. Routinely detectable elements (present in at least 50% of cells) included Mg (overall mean 112 mmol kg−1 dry mass), Si (1850), P(313), S (113), Cl (92), K (300) and Ca (56). Peaks of Na and Al were also frequently present. Individual elements showed a wide range of intracellular concentrations at each depth within the lake. Si had a clear bimodal distribution at depths of 1–8 m, indicating both low-Si (mean concentrations 54–290 mmol Si kg−1) and high-Si (2770–3800 mmol Si kg−1) cell subpopulations. Low-Si cells had significantly higher concentrations of other detectable elements compared with high-Si cells, but could not be distinguished from the latter in terms of morphology or stage of cell cycle (comparison of dividing and non-dividing cells). High-Si cells were intermixed with low-Si cells in individual Anabaena colonies and decreased proportionally with depth, ranging from approximately 75% in the surface sample to 10% at 8 m. With the exception of Si, mean elemental concentrations of Anabaena populations were closely similar throughout the epilimnion. These differed from the metalimnion sample, which had significantly higher concentrations of Mg, P, S and K, and a lower concentration of Si. Mean ratios of certain elements (Mg, P, S and K) and ion groups (monovalent/divalent cations) were highly constant throughout the sampled water column. At each depth, most of the cell elements were significantly and positively inter-correlated (Pearson analysis), with Mg, P, S and K typically constituting the major group (factor analysis). Correlations with Si were invariably negative, suggesting a separate (possibly cell wall) location of this element in the cell.

Following a precultivation with pedospheric nitrogen nutrition, Ricinus plants were supplied with nitrogen solely by spraying nitrate or ammonium solution onto the leaves during the experimental period. The chemical composition of tissues, xylem and phloem exudates was determined and on the basis of the previously determined nitrogen flows (Peuke et al., New Phytologist (1998), 138, 657–687) the flows of potassium, sodium, magnesium, calcium, chloride and ABA were modelled. These data, which permit quantification of net-uptake, transport in xylem and phloem, and utilization in shoot and root, were compared with results obtained in plants with pedospherically-supplied nitrate or ammonium and data in the literature. Although the overall effects on the chemical composition of supplying ammonium to the leaves were not as pronounced as in pedospherically supplied plants, there were some typical responses of plants fed with ammonium (ammonium syndrome). In particular, in ammonium-sprayed plants uptake and transport of magnesium decreased and chloride uptake was increased compared with nitrate-sprayed plants. Furthermore, acropetal ABA transport in the xylem in ammonium-sprayed Ricinus was threefold higher than in nitrate-sprayed plants. Additionally, concentrations of anions were more or less increased in tissues, particularly in the roots, and transport fluids. The overall signal from ammonium-sprayed leaves without a direct effect of ammonium ions on uptake and transport systems in the root is discussed.