Hi Y'all!

I have a bunch of the disposable plastic storage containers (GLAD, other manufacturers, etc) in my kitche, and said to myself, "Self, these would be wonderful for flasking (especially replating) orchids." The letters by the recyling symbol embossed on the container reads "PP" and I asssume this means polypropylene. So I autoclaved one at 121 degrees for 20 minutes. AND IT LIVED! No melting or structural defects! :Party:

These things come in alot of sizes, and are CHEAP! Problems might be venting the lids (Adhesive filtration patches would work great) and possibly te colored lids, though you can get them with red lids, which should help with growth.

Brian Monk, DVM

Ft.Lauderdale, FL

Yep, pp are polypropylene. They have no problem with autoclave. But they have many grade and some may change color if kept under light for a long time. You also have to make sure they are UV stabilized if you they are to be kept outside under natural light.
Drill a hole and get a venting cap and you're set!

Interesting, let us know how it goes

Dr. Monk,

I've been thinking about trying the same thing for a while; the container size seems so much more manageable than glass jars. But let me make sure I've got you right here: They were autoclaved at 121 CELCIUS and survived?

I've heard that there's a type of band-aid that works well as a gas exchange filter for this sort of thing. I've never tried it myself, but they can also be autoclaved. Apparently the best are Round 3M Nexcare Active "spots", but again, I don't have any personal knowledge of this. As soon as my next seed pods are ready, I'm going to give them a try, though :)

Matt Gore

121 degrees as the temp guage on my office autoclave reads. I think this is 121 celsius, but I'll check.

Yep! 121 C sounds about right. That would be about 249.8 F. Hot enough for your altitude.
Dean Stock

Be careful of the Dioxin given off. It is involved in breast cancer. God knows how it would affect plant life.

If I'm not mistaken, PP were created as an alternative to PVC because it has very little dioxin. They are chlorine-fre plastics. Dioxin in PP will be released off at 60dC, so putting it in autoclave at 120dC should help release some dioxin.
When applying as tissue culture vassel, we never let the temp get that high (60dC) so the plant should be safe from any dioxin left over being release.

Hi group,
I thought I should just post to clear a few things up.

Sorry but I have never heard that food grade polypropylene containers give off significant levels of dioxin when
heated to 121 deg C.
Can you direct me to any papers published in a scientific journal that you can quote showing the risk to plants or those autoclaving it?

In the USA and EU polypropylene is coded PP5 on containers, many sauces are prepared at above 100 deg C.
Such polypropylene is designed to be used with food. Such food remains in contact with the plastics during storage.

Polypropylene is autoclavable at 121 deg C.
It is widely used in the medical industry and companies such as Nalgene recommend autoclaving as a sterilizing route.
It has been designated as a safe product for health, drug and medical labware.

Back in early 1980' there was some worry about the effect of phthalates and plant growth. A paper was published in the New Scientist by Drs Hardwick and Cole. (New Scientist 30 Jan 1986) regarding work done at NVRS Warwick UK. The paper does not have specific relevance here, but was brought up in passing as we are discussing plastic toxicity.

However since then legislation in EU has ensured the polypropylene of food grade containers is phthalate free.

With closer reference to plant growth in plastic containers (autoclaved at 121 deg C), there is no indication (that I know of) published in journals, that autoclaved plastics produce dioxins detrimental to in-vitro plant growth. Polypropylene is used widely in the in-vitro and plant tissue culture industry. Many plant pots are polypropylene

With specifics to Paphs...we have been using autoclaved polypropylene containers (heated to 121 deg C) for over 10 years to produce tens of thousands of seedlings with no phytotoxic problems.

With regards red plastic covers changing the spectrum for Paph seedlings. If it helps...we explored that route in the 'light of red Phytatrays' released by Sigma back in 1996. We found no significant benefit. Infact the reduced light transmission slowed growth. Light is not so important to in-vitro seedlings as it is to ordinary plants as photosynthesis is only part of the carbon route to growth.

With regards
Alan Winthrop

Thanks Alan. Your comments mirror my experience with plastics and both plant and human cell culture. I know of no scientific evidence to the contrary.
Dean Stock

Alan, no doubt you have a lot of experience. I'm all for PP for tissue culture and never experience or heard of any problem with PP in this matter.
I've had this discussion with some of my friends who work for the ministry of health in Thailand they their data, which are international standards set specs max heat for PP at 120dC. At the same time they state that 120dC autoclave does not pose any problem for PP and it is practice in all medical industry. He also stated that any dioxin would be release at that point, if any, and would affect its after use.