The importance of some inorganic components of sea water for the turgorregulation of Cbaetomorph¢ linura (Chladophorales). Some algae of the intertidal zone are capable of regulating their turgor pressure. In 1896 DxEvs had already shown that this process is affected primarily by accumulation (positive turgor-regulation) or extrusion (negative turgot-regulation) of mineral salts and that transformation of stock material (e. g. starch) into osmotic active substances (e. g. sucrose) and vice versa plays no important role. His results are being confirmed by the present paper. In Chaetomorpha linurn (MOLLER) KOTZINC, lowering of salinity resulted in a significant release of potassium and chlorine (negative turgor-regulation). Changes in sodium content were only small. In algae exposed to a salinity of 30°o, the total sodium concentration was only about 10% that of the external medium. Salinity increase ted to a marked accumulation (positive turgor-regulation) of potassium and chlorine. Even in this process sodium was engaged only to a small degree -despite its high concentration in the surrounding medium. In both cases internal changes in sodium content amounted only to about 5 % of the total osmotic changes in the external medium. Aiter transfer from 30 %0 salinity into isosmotic artificial sea water without Ca", a rapid loss of potassium and chlorine was observed. The abrupt decrease of the calcium content accompanied by a marked swelling of cell walls, leading to a significant reduction of cell space, is interpreted as ion exchange process changing the cell wail Ca" against Na.EINLEITUNG

The inorganic chemical composition of the cell sap of Coscinodiscus granii (Bacillariophyceae, Centrales). Cells of Coscinodiscus granii of about 200 #m diameter were cultivated at 13 ° to 17 ° C in 10-i flasks filled with nutrient solution of about 32 %o salinity according to v. STOSCH & DRESrS (1964). Illumination was provided by fluorescent lamps (12 hours per day) in combination with daylight. Brightness and quality of irradiation were subjected to considerable changes (2000-6000 lux), simulating ecological conditions. At a diatom concentration of about 10 cells/ml, the material was sifted off by plankton cloth (meshwidth 50 ~tm) and rinsed by isotonic LiCl-solution. Further treatment for cell sap preparation was performed as described by KrSSEL~R (1967). As in C. wailesii, potassium was accumulated up to about 50 times of its medium concentration, while sodium was reduced to about 10 °/0. Chloride distribution was equal in cell sap and medium. Similar values were obtained in C. wailesii. In addition to the methods employed in this species, nitrite, nitrate and silica were also determined. While NO2' was detected only in traces, NOB' was present in considerable amounts (about 0.0225 Val/1). The Estimations of silica, however, were low, seemingly due to the fact, that only orthosillcate and straight chain polymers of not more than 3 Si atoms will react with molybdate. The ready formation of Si-compounds, nonreactive under the conditions of the method employed may help to explain the deviation of the cation: anion relation from stoichiometric unity. The density of artificial sap prepared according to the analytical results exceeds the density of the medium by about 1.2 mg/cm ~. It provides, therefore, no satisfactory explanation for the flotation of diatoms. EINLEITUNG

Collection of cell sap, AFS (apparent free space) and vacuole concentration of the osmotically most important mineral components of some Helgoland marine algae. Samples of cell sap in amounts suitable for chemical analysis of mineral compounds were obtained by high speed centrifugation of several frost-killed (-200 C) He!goland algae under paraffin oil. In order to calculate the vacuole concentration of the mineral salts determined in these liquids, the extravacuolar solving space of the algae was measured as Lithium apparent free space (Li-AFS) after rinsing the algae for severaI minutes in balanced LiCI solutions. The Li-AFS was calculated from the results gained by flamephotometric determination of the Li-concentrations in the sap and in the bathing fluid. To avoid errors caused by interaction of Donnan-effects, the Li-AFS of Chaetomorpba linum kept in diluted sea water of different concentrations was measured. By plotting the results against the medium concentration, evidence was obtained to show that in 100 °/0 Li-solution (corresponding osmotically to natural sea water of about 30 %), the Donnan effect was negligible. In the more diluted solutions, however, higher Li-AFS values were obtained. This would indicate that the differences in the distribution of Li-cations between medium and AFS, whi& are effected by the negative charges of indiffusible anions in the cytoplasm and of fixed acidic groups (e. g. R-COO-) of phycocolloids in the wall material, will cause considerable errors if Li-concentrations are too low. Taking these experiences into account, AFS-values of several algae from Helgoland were measured by the same te&nique and the vacuole concentrations of the analysed mineral compounds calculated. EINLEITUNG

Investigations on the chemical composition of the cell sap in the diatom Coscinodiscus,wailesii (Bacillariophyceae, Centrates). A sample of cells of the plankton diatom

The selective adsorption of the cations Na +, K +, Mg ++ and Ca + + by the cell wall of the Mediterranean alga Valonia utricularis (Siphonocladales, Chlorophyceae) from sea water of 40 Too S was investigated by extraction of cell-wall preparations, eluted before in 1.1 mol methanol {adjusted to pH 8) with 0A n formic acid in a Soxhlet apparatus. Na + and K + were determined by flame photometry, Mg ++ and Ca + + by complexometric titration with EDTA. From calculation of the dry weight:fresh weight ratios and the chloride determinations in the eluates, the Donnan freespace fraction of the total cell-wall volume was calculated to about 35 %, and the analytical results of the cation concentrations in the extracts expressed as ~Val cm -3 DFS. This calculation is based on the assumption that the acidic groups of the noncellulosic matrix material, carrying negative charges by dissociation at the reaction of sea water (ph about 8) are responsible for the adsorption of cations by exhibition of a Donnan effect. The results obtained show clearly that besides the divalent cations Mg ++ and Ca + +, which according to the physico-chemical laws of the Donnan distribution must be relatively accumulated to the second power of the monovalent ones, potassium is also enriched by selective adsorption, and the K + :Na + ratio increased significantly compared with that in sea water. This seems to indicate that the strength of attraction between the cations and the negative sites is dependent on the radii of the ions and the state of hydration and/or polarisation of the ions and binding sites.