i am in a very perplexed position. i have carried out the SOD assay using the NBT method. if im not wrong, the control solution (without plant sample) should give the darkest colour after 15 minutes of reaction time, while hte rest of the plant samples should be lighter, assuming the samples had some amount of SOD enzyme.
but instead, 2 of my plant samples became darker than the control solution. please help, i do not know what to do.