The 36-year-old identified only as Halil D. Faces up to 10 years jail if found guilty by a state court in the western city of Frankfurt of having planned a potentially lethal attack.
Police in a raid last April found a pipe bomb packed with nails and metal ball bearings, as well as weapons, ammunition and dangerous chemicals, in the basement of his building in Oberursel near Frankfurt.
Prosecutors claimed there was a "jihadist motivation" behind the alleged plot to commit a "serious subversive act of violence" and said D. Had ties to Germany's ultra-conservative Islamic Salafist community.
The couple had provided the shop with false personal details, said police.
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Authorities, fearing a bomb attack plot, cancelled a professional bicycle race that had been planned in the area for May 1.
The suspect's wife was also detained but released in July after she claimed she did not know about the materials her husband kept in the basement and said they bought the chemicals to remove mould.
The man in the dock declined to speak and was fined USD 217 for refusing to stand despite repeated requests from the presiding judge.
The trial, held under tight security, was expected to call scores of witnesses and experts and run for 30 days of hearings until mid-June.