From Mother Earth News:
“The report I ran across discussed the effects of bathing radishes in ultrasound. One flat of seeds was placed in an environmentally controlled chamber with 50,000 CPS ultrasound piped in at an output of about one watt; the second group (called a control) was set in an identical chamber but did not receive exposure to ultrasound. Artificial lighting was switched on in both chambers for 12 hours each day (during which time the experimental flat received ultrasound). Both groups were watered and cared for equally.
After about seven days, the seeds in both trays began to sprout. One week is just about the normal germination period for radishes, so up to that point in the experiment, ultrasound didn't seem to offer any benefit.
It soon became apparent, though, that the seedlings receiving ultrasound treatment were growing much more rapidly than their control counterparts. In fact, by the fourteenth day the experimental plants were half again as tall as the ones in the "quiet" chamber.
The experiment continued for 28 days, the same period of time used in the photovoltaic root stimulation tests. By the end of the test, the plants treated with ultrasonic vibrations had grown an average of 87% taller than their control cousins. (The actual growth rates are shown in graphic form in Fig. 2.) Repetitions of the experiment were run to confirm the initial results, and some of the later tests showed growth rate increases of as much as 150%!
It isn't exactly clear why ultrasound stimulates plant growth. Evidence seems to support the theory that the sound acts as a catalyst, activating the production of plant hormones called auxins. As was the case with photovoltaic root stimulation, however, concrete explanations will have to wait for further research.”
Read more: http://www.motherearthnews.com/Sustainable-Farming/1984-05-01/High-Frequency-Sound-Uses.aspx#ixzz1eZeKJVtl
From: http://www.motherearthnews.com/Sustainable-Farming/1984-05-01/High-Frequency-Sound-Uses.aspx
Here is a report that reinforces the positive effects of ultrasound on plants:
“Beneficial effects of ultrasound on plants—a review
A.G. Gordona, b
a Forestry Commission Research Station, Alice Holt Lodge, Farnham, Surrey, UK,
b Formerly at the Department of Plant Science, University of Manitoba, Canada
Available online 2 October 2002.
Abstract
A significantly beneficial effect of ultrasound can be produced in plant material, but it is clear that the causes of, and inconsistencies in, the effect are barely understood.”
From: http://www.sciencedirect.com/science/article/pii/0041624X71901247
I also found this report where insonification by ultrasound caused damage to plant roots:
From:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2149298/
I am not qualified to say this is "mainstream science", but I remain skeptical.
