| Summary: | In part I we established Thiel-Beilby model of the <em>Chara</em> action potential (AP). In part II the AP is investigated in detail at the time of saline stress. Even very short exposure of salt-sensitive <em>Chara</em> cells to artificial pond water with 50 mM NaCl (Saline APW) modified the AP threshold and drastically altered the AP form. Detailed modeling of 14 saline APs from 3 cells established that both the Ca<sup>2+</sup> pump and the Ca<sup>2+</sup> channels on internal stores seem to be affected, with the changes sometimes cancelling and sometimes re-enforcing each other, leading to APs with long durations and very complex forms. The exposure to salinity offers further insights into AP mechanism and suggests future experiments. The prolonged APs lead to greater loss of chloride and potassium ions, compounding the effects of saline stress.
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