On the bleach: stressed plants generate hydrogen peroxide (in the so-called "respiratory burst"). Bleach (hypochlorite) reacts with hydrogen peroxide to form singlet oxygen. Singlet oxygen degrades plugs in conductive elements, kills invading microbes, and probably has other physiologic effects (maybe similar to "signalling" by hydrogen peroxide). Whether these known properties are causal is theoretical. But like your students' observations, I've used diluted bleach to revive wilted cut-flowers!
> ----------
> From: dstarret at BIOLOGY.SEMO.EDU[SMTP:dstarret at BIOLOGY.SEMO.EDU]
> Sent: Wednesday, September 16, 1998 1:35 PM
> To: plant-ed at net.bio.net> Subject: Flower anecdotes
>> Edders,
> We got off onto a tangent in plant anatomy today (often the best lectures
> I do!). Students were chipping in with their home remedies for keeping
> flowers alive. Of the ones that interested me were: Salicylic acid,
> vinegar, lemon juice, 7-up, and bleach. I have an inkling about salicylic
> acid, the rest... It wasn't clear what these were supposed to do, but the
> story is that all somehow aid in making flowers last, bloom better, etc.
> Anyone know of these, what they do, or how they do it?
>> Dave Starrett
>>> *************************************************************
> * *
> * Dr. David Starrett *
> * Biology Department, MS 6200 *
> * Southeast Missouri State University *
> * Cape Girardeau, MO 63701 *
> * Ph: (573) 651-2382 *
> * Fax: (573) 986-6433 *
> * email: dstarret at biology.semo.edu *
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>>
