Today in class we did an experiment to observe mitosis and calculate a mitotic index for the cells at the apical meristem of a garlic root. We first added ethanoic alcohol before adding ethano-orcein stain and heating it, before putting it on a slide, adding some more stain, and viewing it under the microscope.

I understand we add the stain to make it look clearer under the microscope, but what is the purpose of the alcohol (sometimes we use hydrochloric acid)? Is it to break down the cell so the stain can enter easily?

But I didn't think too much about this idea because under the slide the cells appeared distinct, so they can't have been broken down.

I couldn't figure it out, and google searches i made about the experiment only came up with methods and conclusions rather than explaining why the alcohol/acid was added. So would much appreciate it if you could explain why?

Thanks a lot!

The alcohol and acid are for fixing the tissue and making it easier to stain it. Neither damages the tissue.

Tom, alcohols such as ethanol and methanol can alter cell mebrane permeability to various substances by interacting with lipids. The effect is concentration-dependent.