It was a picture-perfect event, with music, food and about 1,000 guests. But the party was bittersweet for General Motors of Bowling Green. General Motors marked its 100th year of operation recently, and the GM Bowling Green Assembly Plant celebrated the centennial in the midst of production cuts and layoffs that could affect about 70 employees. The Bowling Green plant will shut down to prepare employees and equipment for a production slow-down; the plant will reduce the number of vehicles it produces from 18.5 to 15 per hour. Layoffs will affect the plant's newest hires.