Hi Ian, you can use plastic bottles for tissue culture, but not all kinds of plastic, if you want to heat sterilize your equipment and media. Polypropylene will surely melt. What you can use are the polycarbonate plastic bottles, the stuff with which baby milk bottles are made, so that they can be boiled and sterilized ( Actually I have myself done some tissue culture in baby bottles with the silicon nipples, its actually very practical for sowing with a syringe), anyways glass jars are cheaper than polycarbonate bottles and I would recommend using those. If at all you want to use cheap polypropylene plastic bottles, then you will have to sterilize them with 10% bleach or 0.5% HgCl2 followed by washing them with sterile distilled water, all under aseptic conditions. Not to mention you will have to add separately sterilized media into the bottles. Believe me using glass jars will be cheaper and easier.