Thanks . . .
Quite to the contrary, I have found PPM (Plant Preservative Mixture) economical to use for a number of reasons -- chiefly its very predictable success in the establishment of TC cultures, with no issues (in my experience) with either vitrification or phenolic bleeding when used with cuttings: an all-too-common occurrence with bleaching, hydrogen peroxide, and peracetic acid sterilization practices. Also, the lion's share of failures I have seen with those pursuing
Nepenthes culture -- especially for the first time -- have
always stemmed from over-bleaching. I cannot tell you the number of photos and queries sent my way in the last couple of years -- shots of all-too sterile cultures with very dead translucent seed; and considering the work I have done with some expensive material for clients over the years, PPM has proved to be highly predictable and consistent. There had been some discussion -- more lip-flapping than anything else -- that its use (either in media or simply as a disinfectant) could inhibit germination; but I have not found that to be the case (
http://icps.proboards.com/index.cgi?board=tissue&action=display&thread=5073).
I currently use four and eight percent solutions of PPM (though I have experimented with others), mixed with thirty percent MS (regardless of what your final media will be) -- just the salts dissolved in distilled water -- no sucrose, PGRs (plant growth regulators), or pH adjustment. I generally make small batches, usually not exceeding 50 ml at a time (so only 2 ml of PPM is used for 4% and 4 ml for 8%). Both solutions can be reused upwards of six times (the mix filtered between use and kept refrigerated) For highland
Nepenthes, four to six hours in 4% percent seems to be effective; for lowlanders, twelve hours or more in 8% percent (the seed typically being far more contaminated by algal and mold issues than their highland counterparts -- even if freshly-collected).
For
Dionaea,
Sarracenia, or
Heliamphora seed (or leaves or rhizomes), I would treat them as though highland
Nepenthes.
As an aside, my 2011 contamination rate with that methodology was 1.05% -- and there were hundreds of cultures . . .