[APD] Help needed ... understanding results in science project about aquatic plants!

[Shireen Gonzaga <whimbrel at comcast_net>]

Hi ... I've been helping my middle-school neighbor with his science  
project. He's testing the effects of different fertilizers and  
pesticides on aquatic plants.

He has 7 jars set up with Water Sprite, under 2x 40W T-12 fluorescent  
lights for 12 hours/day. We picked out 7 plants similar in size/age  
for the project. (There were hardly any plantlets on the leaves --  
these were relatively young and very healthy plants, about 7-8" long.  
I've been growing water sprite for many years and have become  
familiar with their growth characteristics in aquariums. Most  
plantlets develop on mature leaves, and as the plantlets grow, the  
parent leaf deteriorates.)

The experiment is still in progress, and will end on Jan. 31st. One  
plant serves as a control. The other jars get small daily doses of  
the following: nitrate, phosphate, Tide w/Downy laundry detergent,  
malathion, pyrethrin, and a pesticide. As an added bonus, the plants  
had lots of pond snail eggs so he is also able to observe the effect  
of these substances on the newly-hatched snails.

It's currently two weeks into the experiment; the control, nitrate,  
phosphate, and pesticide plants seem to be OK. The main leaves have  
grown a bit larger, which is normal growth. The malathion plant was  
first to succumb. However, we're seeing something interesting in the  
plants dosed with Tide and pyrethrins.

For the Tide plant, mature leaves have all turned brown. However,  
there's been a profusion of plantlets sprouting from the brown adult  
leaves. Those plantlets are starting to show patches of brown, and  
will probably be dead in a few days.

For the pyrethrin plant, the mature leaves are still green but there  
are many plantlets sprouting from them -- not as many as the Tide  
plant, but still, a surprisingly large number of plantlets compared  
to the control plant.

I've been googl'ing around trying to understand the unusual growth in  
these two cases, but it's hard to understand what's going on because  
I don't have a background in botany and chemistry. I'm hoping that  
more knowledgeable people on the list can shed some light on what's  
going on.

Tide case: we know that the detergent has "enzymes" for getting rid  
of stains, including grass stains. So I'm assuming that these enzymes  
are attacking the mature leaves, causing them to turn brown. But  
what's causing so many plantlets to pop out? Is it caused by a  
chemical trigger in the detergent? Could it be that there's a built- 
in chemical trigger in stressed parent leaves to create plantlets  
before they turn brown and die?

Pyrethrin case: this compound is extracted from chrysanthemum  
flowers. Pyrethroids are the synthetic version of that natural  
compound. They destroy bugs by messing with their nervous system.  
(http://npic.orst.edu/factsheets/pyrethrins.pdf ) There's also  
concern about the compound's effect on aquatic animals like fish and  
crustaceans (http://www.sciencenews.org/articles/20060204/bob9.asp).  
According to an abstract at http://www.pubmedcentral.nih.gov/ 
articlerender.fcgi?artid=1566380, pyrethroids are hormone disruptors.  
Although the paper is about its effect on breast cancer cells, I'm  
wondering if there's a similar mechanism in pyrethrin/pyrethroids  
pushing the plant's asexual reproduction into overdrive?

If anyone has additional information, names of scientists we could  
contact for more information, and/or references that could help us  
understand the results of the exposures to TIde and pyrethrin, please  
post or email me at whimbrel at comcast dot net.


thanks!
   shireen


Shireen Gonzaga
Baltimore, MD
whimbrel at comcast dot net



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