1. The problem statement, all variables and given/known data So we did an experiment where we put a leaf section in KCl and another leaf section in NaCl. There was a marked difference in the percent of stomata that opening between the two. We let the two sections sit in solution for 60 mins each. The leaves in KCl had almost twice as many stoma open as the leaves in NaCl. Both were the same pH and had equal light exposure. The measurement areas were of roughly equal size. That said, the key difference was the presence of K+ ions as opposed to Na+ ions. Now - I can't figure out why the two ions would produce such different results. Any ideas? 3. The attempt at a solution I think it has something to do with on being positive and the other ion being negative. Though, I can't explain it in terms of the osmotic potential between the extracellular and intracellular regions, which cause the water to flow to regulate the guard cells of the stoma. Does K+ create higher osmotic potential which then means more water movies into the guard cells - thereby increasing the stomatal opening and therefore CO2 uptake, which means a higher photosynthetic rate? Or have I got this completely wrong? I've looked for lit on this topic and it's very limited, if at all existent.