can you explain how to handle the Imagej software with light...

Hi Prashant, the principle behind using ImageJ or CellProfiler is essentially the same. Since I prefer CellProfiler, I would recommend trying with that (http://www.cellprofiler.org/). You will notice that they have extensive tutorials and FAQs which can be applied to any type of image analysis, not just ROS staining with DAB. Briefly, CellProfiler has a tool with which you can manually identify regions of interest on your leaf. In the case of DAB, you would use pixel intensity. Over a certain pixel intensity threshold, you would set the identification as "DAB stain". Next, you can feed as many images as you like into that pipeline and it will sort based on the threshold you set. With this, you can get a quantitative assessment of the amount of staining in your tissue. Please let me know if this helped answer your question.