Some interesting developments in the health effects of wireless microwave radiation:
This Slashdot comment has an excellent theory as to why this happens:
I remember watching a TED talk a while back about a fellow who was perfecting an electromagnetic cancer-killing device that was looking to be extremely effective (Bill Doyle: Treating cancer with electric fields). Perhaps a similar phenomina is in play here. Basically part of the DNA duplication process prior to cell division involves stringing out the chromosomes into long electrostatically-bonded chains. By electromagnetically interfering in that process the device caused virtualy all replicating cells to die, with the few survivors typically being extremely sickly. Since in most parts of the body cancer cells are the only ones replicating with any frequency the device presented a method of selectively destroying cancer cells without significantly harming the surrounding tissue. Initial studies done on people with inoperable or recurrent tumors showed success on par with intensive chemotherapy, but without the horrible side effects.
So anyway - we know that at least some EM fields are capable of killing replicating cells, and that's kind of the primary activity of embrryonic cells, so that could perhaps be the reason the seeds failed to germinate. Of course I have no idea what the strength, frequency, etc. of the anti-cancer device's EM fields were, so maybe it's not relevant, but something worth considering at least.
Another "attack vector" is that fats typically absorb microwaves far more efficiently than water, and are an important component of cell membranes. That means microwave heating would is actually concentrated on the protective membrane around the cell, and in an embryo that membrane is in the process of growing very rapidly as the initial cell subdivides, and may be more vulnerable to damage.
And another comment with first hand experience:
As someone that has performed similar radiation experiments as part of my research into zero-light horticulture, faking this is very doubtful, as I've encountered the same issues. Germination rates in the area of our facility with wireless access are roughly half of that on the other side of the shed that is totally free of radiation in that frequency range thanks to the natural faraday cage (the entire structure is grounded, metal walls and supports, etc.) that the facility provides. You can't even use your cell phone two feet inside the door.
- Fun fact: the "unlicensed" band of the radio spectrum (which we use for wifi, cordless phones, garage-door openers, doorbells, kids' walkie talkies, etc.) was originally decreed to be "junk" spectrum, since this is the same frequency a microwave oven operates on. Microwave ovens' operating frequency is chosen because it can resonate and heat up water molecules. Therefore, our wifi devices are basically very weak microwave ovens.