The four main factors that affect seed germination are water, oxygen, temperature, and availability of light. Of these four factors, pH would affect water the most. pH is an indicator of where a substance stands in terms of dissociating into hydrogen ions (H+), which would place it on the acidic side, or dissociating into hydroxide ions (OH-), which would qualify it as a base. The pH scale is a scale of 1 to 14, with the neutral point being 7, which is right in the middle. Pure water has a pH of 7, meaning it is neutral, neither acidic nor basic. Of course, most water used to germinate seeds has substances added to it, such as fluorine and chlorine, and these substances can affect the pH of the water. Seeds will still germinate, but will do so at different rates, as the fluctuating pH in the water can slow the process down a bit. As with most substances, too much on either end of the pH spectrum would probably have disparaging results on seed germination, resulting in little to no germination for extreme pH levels.