Plasmas in saline solution driven by a repetitive bipolar pulsed power source are studied. We use a negative pulse to generate electrolytic gas with a controllable amount, followed by a positive pulse to ignite the plasma. With an increase in the negative voltage pulse amplitude from 0 to -80 V, we observed an increase in the amount of electrolytic gas (hydrogen) formation, resulting in a reduced time delay, from 65 to 6 mu s, required to ignite the plasma upon the onset of the positive pulse. A decrease, from 1.75 to 1.0 A, in the peak currents within the positive voltage pulse is also observed. Optical emission spectroscopy shows that the intensity ratio of the H-alpha (656 nm) to Na (588 nm) emission lines increases from zero to 0.0035. These observations can be well explained by the increase in the gas coverage on the electrode surface and the change in the gas composition within which the plasma is ignited with the application of the negative pulse.