"Wayne Turville" <[EMAIL PROTECTED]> yelled so
loud we picked it up in Arizona:
>I am having a little difficulty with conflicting advise as to what
>chemicals,at what strength and for what period of time to soak dry orchid seed
>Here in Australia we have product called 'White King" Bleach
>I have been recommended to use between 4% to as high as 25% from
>various other labs around Australia
>Its percentage of Sodium hypochlorite is 42 grams per
>liter. Sorry USA guys metric here!
>The dry seed is emersed in a solution of white king and water,but
>the solution rates vary wildly.
>
>I have tried Calcium Hypochlorite, Benzocodium Chloride (forgive
>the incorrect spelling ) But I am having wildly varying success.
>Can someone guide me as to the correct rates and times for dry seed.
>
>I have been advised 10 minutes soaking time is correct.
Unfortunately there is no flat figure for concentration and
time when it comes to seed disinfection. Fresh seed with some amount
of retained moisture from the capsule may sink relatively quickly,
meaning that the disinfectant has penetrated the testa and thoroughly
wetted the seed. Seed that has been stored dry and cold for several
years will be much more resistant to wetting, and I frequently use an
ultrasonicator to improve penetration.
A good starting place is 10% bleach solution (commercial
bleach locally being a 6% solution of sodium hypochlorite in water)
for 10-15 minutes; rinse 1-2 times with sterile distilled water, and
deposit on fresh medium. If there is contamination, increase duration
incrementally until clean cultures are achieved.
Also note that seed that has been treated properly
(collected when fresh onto CLEAN dry paper, handled as little as
possible, dried as quickly as reasonably possible, etc.) will be much
easier to disinfest than seeds that have not been. Sometimes
treatments of 30-45 minutes with sodium hypochlorite are not enough,
and sugar hatches are required (soak in dilute sucrose solution for
24 hours, THEN hit with bleach solution). There is also
dichloroisocyanuric acid (which goes by about 5-6 different names),
the "new" pool chlorine, which forms a mildly acidic solution. This
throws the pH from alkaline (bleach) to acid, which in turn causes
the chlorine to predominate in the form of hypochlorous acid, with
~80x the "killing" power of hypochlorite (in some tests).
Do not try to acidify bleach solutions to achieve the same
result- not without a fume hood or a desire to chlorinate the neighborhood.
-AJHicks
Chandler, AZ
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