The influence of metallic, cations (added at 10 μM‐1 mM) on the uptake of orthophosphate from 0.2–10 μM solution by Synechococcus leopoliensis (Racib.) Komarek was investigated. All cations tested except Mg2+ and Zn2+ stimulated phosphate uptake. The most pronounced stimulation of phosphate uptake was caused by Ca2+·Ca2+ markedly decreased the half‐saturation concentration for orthophosphate uptake, apparently by acting upon the metabolic processes of phosphate transport into the cell. Phosphate did not influence Ca2+ fluxes across the cell‐surface.

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Phosphate-limited growth of the blue-green alga Synechococcus leopoliensis was unaffected by arsenate at up to 200 μM. Phosphate uptake, during growth and also under nongrowing conditions, was not measurably affected by arsenate even at 50 × the phosphate concentration. Arsenate uptake was very low and was not influenced by light or by external phosphate. It is concluded that phosphate transport in Synechococcus is highly phosphate specific. The ecological aspects of this specificity are briefly discussed.

Anacystis nidulans (Richt.) Drouet & Daily (UTEX 625), grown in batch culture with 0.5% CO2 in air, was supplied with chloride labelled with 36Cl in light and dark. Uptake in light was stimulated relative to uptake in darkness. A single transport system for Cl− with an apparent Km for Cl− of 0.14 mM was identified. Chloride in the cells reached a maximum value after 30–50 min at 25 C. At this point the internal Cl− concentration was calculated to be 60‐fold the external (0.1 mM) in light and 37‐fold in darkness. DCMU (3‐[3,4‐dichlorophenyl]–1, 1‐dime‐thylurea), at concentrations which abolished photosynthetic O2 evolution did not inhibit Cl− uptake in light. Carbonyl cyanide m‐chlorophenyl hydrazone (CCCP), at uncoupling concentrations for photosynthesis and dark respiration, strongly inhibited Cl− uptake in light and darkness. N,N'‐dicyclohexyl carbodiimide (DCCD), an energy transfer inhibitor, inhibited light Cl− uptake more slowly than photosynthesis but had no effect on dark Cl− uptake. It is concluded that Cl− uptake in A. nidulans was active in light and darkness, and that ATP was the probable energy source for transport.

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