Effects of potassium concentration and osmotic pressure of sea water on the cell-turgor pressure of Chaetomorpha linum

The unicellular littoral alga Chaetomorpha linum is especially capable of maintaining its cell-turgor constant by regulation of the internal osmotic pressure, when the salinity of the sea water is altered. The decrease or increase of the external potassium concentration is seen to be an important cause of this turgor regulation, as well as the alteration of the external osmotic pressure, which was already known to be an important factor. This has been shown by experiments in artificial sea water with reduced osmolality and variable potassium concentration (1 to 50 mMol/l).