I have recently performed an experiment in which I tested the affects of phytotoxic cations on the rate of germination of the common navy bean. I did this out of curiosity, as I have recently been researching arsenic (III) and arsenic (V) mobility in water systems, and I wanted to know weather or not it was the mobility of the ion or its general toxicity to a cell that is more influential on the overall phytotocicity. Generally, arsenic (III) is much more toxic due to the fact that it is so mobile while arsenic (V) is less toxic due to the fact that it is less mobile. After testing the oxygen usage in each of my different germination environments, I was quite surprised at the results. I had placed 100 navy beans in 1 molar solutions of copper, lead, iron, and cobalt chloride (the lead chloride may have been a little under 1 M, as it is not very soluble in water); in each of these solutions, I let these beans germinate for 12 hours and then tested the oxygen output of each sample. Here were my results:
I did not think the mobility of these ions would have such an effect, as I know lead is less mobile than other cations in water systems; however, my major problem is interpreting the top three results, all of which gave fairly similar results. I am having trouble figuring out where this result is coming from. I know that all of the ions are phytotocic to some degree, and I would expect all of the ions to have a detrimental affect on the germination of the seeds. Is it more likely that these findings are the result of the phytotocicity of the ions or the mobility of the cations across the cellular membrane?