When the ambient atmosphere of Acer pseudoplatanus cells in suspension culture is rapidly changed by opening the culture flasks and gently stirring (*mild gas-shock') or by filtering and suspending in new medium ('strong gas-shock'), drastic modifications of the rates of leucine, methionine, glucose, adenine, sulphate and phosphate uptake are observed. EoMowing the gas-shock, rates of uptake rapidly decrease within a few minutes. Subsequently the rates increase agahi to the initial level within several hours. The uptake of potassium, which is known to be passively distributed between the medium and the interior of many plant cells, at least at high external concentrations, is apparently independent of gas-shock.The shock and recovery kinetics are similar for all solutes investigated (except K"''), in particular for different solutes studied hi double labelling experiments with the same batch of cells. At the maximum of the after-effect of shock, i.e, at minimum rates of uptake, uptake shows a highly reduced dependence on temperature. Gas-shock probably inactivates, denatures, structurally alters or releases membrahe macromolecules engaged in transport. These molecules are then re-synthesized and re-incorporated into the membrane during recovery.

The resumption of solute uptake capacity lost after gas‐shock of Acer pseudoplatanus L. cell suspension cultures is severely inhibited by low temperatures (1°C) and by inhibitors of transcription and translation of protein synthesis such as 2‐mercapto‐1 (β‐4‐pyridethyl) benzimidazole (MPB, 40 μg ml−1), puromycin (around 100 μg ml−1) and actinomycin (100 μg ml−1). Cells that have already attained maximum uptake capacity loose it again after less than 1 h in 40 μg ml−1 MPB. Gel‐electrophoresis of the external media of the cells shows that the release of proteins into the solution is affected by shock. The results demonstrate that proteins are involved in the mechanism of solute uptake by the cells, so that these proteins are among the factors altered during shock and recovery, and are important for the understanding of the after‐effects of shock.

No abstract

At concentrations of 10~^M, Li* inhibits the recovery of solute uptake capacity of Acer pseudoplatanus L. cell suspension cultures after gas-shock (i.e. after rapid exchange of the atmosphere in the culture flasks for ambient air). It also reduces solute uptake capacity of cells having already attained high rates of uptake during recovery from gas-shock. The effects of Li"^ are much greater in cells which have been cultivated in 7 mM K* solution than in cells cultivated with higher K* levels (19 mM). Increasing K"^ concentration during recovery reverses the effect of ICr'M Li* and, with sufficiently high concentrations of K* (^ KT'M) during recovery, the solute uptake capacity of the fully recovered cells can even become greater than that of the control, at least for the low values of substrate concentration (here sulphate 10~'M). Since Li* does not affect the time course of solute uptake measured over 15-20 min. it is thought that it interacts with the synthesis and turnover of the solute uptake machinery of the Acer pseudoplatanus cells. Thermodynamic analysis of the flux data also supports the hypothesis that Li* inhibits the biosynthesis of specific sites of solute permeation, but it does not rule out the possibility that K* interferes rather on the forces acting on the transport of the considered solutes than on the catalytic structures of permeation.